diff --git a/.cirrus.yml b/.cirrus.yml
index 7d7c3adfd32..416ad879fc4 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -1,5 +1,7 @@
+only_if: $CIRRUS_TAG == '' && ($CIRRUS_PR != '' || $CIRRUS_BRANCH == 'master' || $CIRRUS_BRANCH =~ 'tokio-.*')
+auto_cancellation: $CIRRUS_BRANCH != 'master' && $CIRRUS_BRANCH !=~ 'tokio-.*'
 freebsd_instance:
-  image: freebsd-12-3-release-amd64
+  image_family: freebsd-12-4
 env:
   RUST_STABLE: stable
   RUST_NIGHTLY: nightly-2022-10-25
@@ -11,7 +13,6 @@ env:
 # the system's binaries, so the environment shouldn't matter.
 task:
   name: FreeBSD 64-bit
-  auto_cancellation: $CIRRUS_BRANCH != 'master' && $CIRRUS_BRANCH !=~ 'tokio-.*'
   setup_script:
     - pkg install -y bash curl
     - curl https://sh.rustup.rs -sSf --output rustup.sh
@@ -26,7 +27,6 @@ task:
 
 task:
   name: FreeBSD docs
-  auto_cancellation: $CIRRUS_BRANCH != 'master' && $CIRRUS_BRANCH !=~ 'tokio-.*'
   env:
     RUSTFLAGS: --cfg docsrs --cfg tokio_unstable
     RUSTDOCFLAGS: --cfg docsrs --cfg tokio_unstable -Dwarnings
@@ -44,7 +44,6 @@ task:
 
 task:
   name: FreeBSD 32-bit
-  auto_cancellation: $CIRRUS_BRANCH != 'master' && $CIRRUS_BRANCH !=~ 'tokio-.*'
   setup_script:
     - pkg install -y bash curl
     - curl https://sh.rustup.rs -sSf --output rustup.sh
diff --git a/.github/workflows/audit.yml b/.github/workflows/audit.yml
index fa0e8d72943..cb124aabdb6 100644
--- a/.github/workflows/audit.yml
+++ b/.github/workflows/audit.yml
@@ -15,15 +15,16 @@ permissions:
 jobs:
   security-audit:
     permissions:
-      checks: write  # for actions-rs/audit-check to create check
+      checks: write  # for rustsec/audit-check to create check
       contents: read  # for actions/checkout to fetch code
-      issues: write  # for actions-rs/audit-check to create issues
+      issues: write  # for rustsec/audit-check to create issues
     runs-on: ubuntu-latest
     if: "!contains(github.event.head_commit.message, 'ci skip')"
     steps:
       - uses: actions/checkout@v3
 
       - name: Audit Check
-        uses: actions-rs/audit-check@v1
+        # https://github.com/rustsec/audit-check/issues/2
+        uses: rustsec/audit-check@master
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a109e9f0023..0c00616005a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,7 +12,7 @@ env:
   # Change to specific Rust release to pin
   rust_stable: stable
   rust_nightly: nightly-2022-11-03
-  rust_clippy: 1.60.0
+  rust_clippy: 1.65.0
   # When updating this, also update:
   # - README.md
   # - tokio/README.md
@@ -42,6 +42,7 @@ jobs:
       - test-unstable
       - miri
       - asan
+      - semver
       - cross-check
       - cross-test
       - no-atomic-u64
@@ -73,13 +74,12 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_stable }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
             toolchain: ${{ env.rust_stable }}
-            override: true
       - name: Install Rust
         run: rustup update stable
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: Install cargo-hack
         uses: taiki-e/install-action@cargo-hack
 
@@ -123,11 +123,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_stable }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
             toolchain: ${{ env.rust_stable }}
-            override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: Enable parking_lot send_guard feature
         # Inserts the line "plsend = ["parking_lot/send_guard"]" right after [features]
         run: sed -i '/\[features\]/a plsend = ["parking_lot/send_guard"]' tokio/Cargo.toml
@@ -140,11 +139,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_stable }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
             toolchain: ${{ env.rust_stable }}
-            override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
 
       - name: Install Valgrind
         uses: taiki-e/install-action@valgrind
@@ -179,11 +177,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_stable }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
             toolchain: ${{ env.rust_stable }}
-            override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       # Run `tokio` with "unstable" cfg flag.
       - name: test tokio full --cfg unstable
         run: cargo test --all-features
@@ -200,12 +197,11 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_nightly }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_nightly }}
           components: miri
-          override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: miri
         # Many of tests in tokio/tests and doctests use #[tokio::test] or
         # #[tokio::main] that calls epoll_create1 that Miri does not support.
@@ -213,7 +209,6 @@ jobs:
         working-directory: tokio
         env:
           MIRIFLAGS: -Zmiri-disable-isolation -Zmiri-strict-provenance -Zmiri-retag-fields
-          PROPTEST_CASES: 10
 
   asan:
     name: asan
@@ -224,11 +219,10 @@ jobs:
         # Required to resolve symbols in sanitizer output
         run: sudo apt-get install -y llvm
       - name: Install Rust ${{ env.rust_nightly }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_nightly }}
-          override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: asan
         run: cargo test --workspace --all-features --target x86_64-unknown-linux-gnu --tests -- --test-threads 1
         env:
@@ -236,6 +230,23 @@ jobs:
           # Ignore `trybuild` errors as they are irrelevant and flaky on nightly
           TRYBUILD: overwrite
 
+  semver:
+    name: semver
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Install Rust ${{ env.rust_stable }}
+        uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ env.rust_stable }}
+      - name: Install cargo-semver-checks
+        uses: taiki-e/install-action@v2
+        with:
+          tool: cargo-semver-checks
+      - name: Check semver compatibility
+        run: |
+          cargo semver-checks check-release --release-type minor
+
   cross-check:
     name: cross-check
     runs-on: ubuntu-latest
@@ -250,16 +261,13 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_stable }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_stable }}
           target: ${{ matrix.target }}
-          override: true
-      - uses: actions-rs/cargo@v1
-        with:
-          use-cross: true
-          command: check
-          args: --workspace --all-features --target ${{ matrix.target }}
+      - name: Install cross
+        uses: taiki-e/install-action@cross
+      - run: cross check --workspace --all-features --target ${{ matrix.target }}
         env:
           RUSTFLAGS: --cfg tokio_unstable -Dwarnings
 
@@ -268,26 +276,35 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        target:
-          - i686-unknown-linux-gnu
-          - arm-unknown-linux-gnueabihf
-          - armv7-unknown-linux-gnueabihf
-          - aarch64-unknown-linux-gnu
+        include:
+          - target: i686-unknown-linux-gnu
+          - target: arm-unknown-linux-gnueabihf
+          - target: armv7-unknown-linux-gnueabihf
+          - target: aarch64-unknown-linux-gnu
+
+          # Run a platform without AtomicU64 and no const Mutex::new
+          - target: arm-unknown-linux-gnueabihf
+            rustflags: --cfg tokio_no_const_mutex_new
     steps:
       - uses: actions/checkout@v3
-      - name: Install Rust ${{ env.rust_stable }}
-        uses: actions-rs/toolchain@v1
+      - name: Install Rust stable
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_stable }}
           target: ${{ matrix.target }}
-          override: true
-      - uses: actions-rs/cargo@v1
-        with:
-          use-cross: true
-          command: test
-          args: -p tokio --all-features --target ${{ matrix.target }} --tests
+      - name: Install cross
+        uses: taiki-e/install-action@cross
+      # First run with all features (including parking_lot)
+      - run: cross test -p tokio --all-features --target ${{ matrix.target }} --tests
+        env:
+          RUSTFLAGS: --cfg tokio_unstable -Dwarnings --cfg tokio_no_ipv6 ${{ matrix.rustflags }}
+      # Now run without parking_lot
+      - name: Remove `parking_lot` from `full` feature
+        run: sed -i '0,/parking_lot/{/parking_lot/d;}' tokio/Cargo.toml
+      # The `tokio_no_parking_lot` cfg is here to ensure the `sed` above does not silently break.
+      - run: cross test -p tokio --features full,test-util --target ${{ matrix.target }} --tests
         env:
-          RUSTFLAGS: --cfg tokio_unstable -Dwarnings --cfg tokio_no_ipv6
+          RUSTFLAGS: --cfg tokio_unstable -Dwarnings --cfg tokio_no_ipv6 --cfg tokio_no_parking_lot ${{ matrix.rustflags }}
 
   # See https://github.com/tokio-rs/tokio/issues/5187
   no-atomic-u64:
@@ -296,11 +313,12 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_nightly }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_nightly }}
           components: rust-src
-          override: true
+      - name: Install cargo-hack
+        uses: taiki-e/install-action@cargo-hack
       # Install linker and libraries for i686-unknown-linux-gnu
       - uses: taiki-e/setup-cross-toolchain-action@v1
         with:
@@ -308,6 +326,14 @@ jobs:
       - run: cargo test -Zbuild-std --target target-specs/i686-unknown-linux-gnu.json -p tokio --all-features
         env:
           RUSTFLAGS: --cfg tokio_unstable -Dwarnings --cfg tokio_no_atomic_u64
+      # https://github.com/tokio-rs/tokio/pull/5356
+      # https://github.com/tokio-rs/tokio/issues/5373
+      - run: cargo hack build -p tokio --feature-powerset --depth 2 -Z avoid-dev-deps --keep-going
+        env:
+          RUSTFLAGS: --cfg tokio_unstable -Dwarnings --cfg tokio_no_atomic_u64 --cfg tokio_no_const_mutex_new
+      - run: cargo hack build -p tokio --feature-powerset --depth 2 -Z avoid-dev-deps --keep-going
+        env:
+          RUSTFLAGS: --cfg tokio_unstable -Dwarnings --cfg tokio_no_atomic_u64
 
   features:
     name: features
@@ -315,12 +341,11 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_nightly }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_nightly }}
           target: ${{ matrix.target }}
-          override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: Install cargo-hack
         uses: taiki-e/install-action@cargo-hack
       - name: check --feature-powerset
@@ -337,11 +362,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_min }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_min }}
-          override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       # First compile just the main tokio crate with minrust and newest version
       # of all dependencies, then pin once_cell and compile the rest of the
       # crates with the pinned once_cell version.
@@ -351,10 +375,14 @@ jobs:
       # release.
       - name: "check -p tokio --all-features"
         run: cargo check -p tokio --all-features
+        env:
+          RUSTFLAGS: "" # remove -Dwarnings
       - name: "pin once_cell version"
         run: cargo update -p once_cell --precise 1.14.0
       - name: "check --workspace --all-features"
         run: cargo check --workspace --all-features
+        env:
+          RUSTFLAGS: "" # remove -Dwarnings
 
   minimal-versions:
     name: minimal-versions
@@ -362,11 +390,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_nightly }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_nightly }}
-          override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: Install cargo-hack
         uses: taiki-e/install-action@cargo-hack
       - name: "check --all-features -Z minimal-versions"
@@ -394,12 +421,11 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_stable }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_stable }}
-          override: true
           components: rustfmt
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       # Check fmt
       - name: "rustfmt --check"
         # Workaround for rust-lang/cargo#7732
@@ -415,12 +441,11 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_clippy }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_clippy }}
-          override: true
           components: clippy
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       # Run clippy
       - name: "clippy --all"
         run: cargo clippy --all --tests --all-features
@@ -431,11 +456,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_nightly }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_nightly }}
-          override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: "doc --lib --all-features"
         run: cargo doc --lib --no-deps --all-features --document-private-items
         env:
@@ -448,11 +472,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_stable }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_stable }}
-          override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: build --cfg loom
         run: cargo test --no-run --lib --features full
         working-directory: tokio
@@ -483,11 +506,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_stable }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_stable }}
-          override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: Test hyper
         run: |
           set -x
@@ -511,12 +533,11 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_nightly }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_nightly }}
           target: x86_64-fortanix-unknown-sgx
-          override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       # NOTE: Currently the only test we can run is to build tokio with rt and sync features.
       - name: build tokio
         run: cargo build --target x86_64-fortanix-unknown-sgx --features rt,sync
@@ -528,11 +549,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_stable }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_stable }}
-          override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: Install wasm-pack
         run: curl https://rustwasm.github.io/wasm-pack/installer/init.sh -sSf | sh
       - name: test tokio
@@ -545,11 +565,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_stable }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ env.rust_stable }}
-          override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
 
       # Install dependencies
       - name: Install cargo-hack
@@ -597,17 +616,16 @@ jobs:
           - ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - name: Install Rust nightly-2022-07-25
-        uses: actions-rs/toolchain@v1
+      - name: Install Rust nightly-2022-11-16
+        uses: dtolnay/rust-toolchain@master
         with:
           # `check-external-types` requires a specific Rust nightly version. See
           # the README for details: https://github.com/awslabs/cargo-check-external-types
-          toolchain: nightly-2022-07-25
-          override: true
-      - uses: Swatinem/rust-cache@v1
+          toolchain: nightly-2022-11-16
+      - uses: Swatinem/rust-cache@v2
       - name: check-external-types
         run: |
           set -x
-          cargo install cargo-check-external-types --locked --version 0.1.5
+          cargo install cargo-check-external-types --locked --version 0.1.6
           cargo check-external-types --all-features --config external-types.toml
         working-directory: tokio
diff --git a/.github/workflows/loom.yml b/.github/workflows/loom.yml
index bd92a1e45a4..0c18e0c3aa8 100644
--- a/.github/workflows/loom.yml
+++ b/.github/workflows/loom.yml
@@ -34,11 +34,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_stable }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
             toolchain: ${{ env.rust_stable }}
-            override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: loom ${{ matrix.scope }}
         run: cargo test --lib --release --features full -- --nocapture $SCOPE
         working-directory: tokio
diff --git a/.github/workflows/pr-audit.yml b/.github/workflows/pr-audit.yml
index 408bc49edf1..d6f798292fe 100644
--- a/.github/workflows/pr-audit.yml
+++ b/.github/workflows/pr-audit.yml
@@ -19,17 +19,10 @@ jobs:
       - uses: actions/checkout@v3
 
       - name: Install cargo-audit
-        uses: actions-rs/cargo@v1
-        with:
-          command: install
-          args: cargo-audit
+        run: cargo install cargo-audit
 
       - name: Generate lockfile
-        uses: actions-rs/cargo@v1
-        with:
-          command: generate-lockfile
+        run: cargo generate-lockfile
 
       - name: Audit dependencies
-        uses: actions-rs/cargo@v1
-        with:
-          command: audit
+        run: cargo audit
diff --git a/.github/workflows/stress-test.yml b/.github/workflows/stress-test.yml
index 9b93fdb67a5..f33cc181b3d 100644
--- a/.github/workflows/stress-test.yml
+++ b/.github/workflows/stress-test.yml
@@ -25,11 +25,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust ${{ env.rust_stable }}
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
             toolchain: ${{ env.rust_stable }}
-            override: true
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: Install Valgrind
         uses: taiki-e/install-action@valgrind
 
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index a3c1c91084e..7681ef9da23 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -187,7 +187,7 @@ LOOM_MAX_PREEMPTIONS=1 RUSTFLAGS="--cfg loom" \
 
 You can run miri tests with
 ```
-MIRIFLAGS="-Zmiri-disable-isolation -Zmiri-tag-raw-pointers" PROPTEST_CASES=10 \
+MIRIFLAGS="-Zmiri-disable-isolation -Zmiri-tag-raw-pointers" \
     cargo +nightly miri test --features full --lib
 ```
 
@@ -209,6 +209,31 @@ utilities available to use in tests, no matter the crate being tested.
 The best strategy for writing a new integration test is to look at existing
 integration tests in the crate and follow the style.
 
+#### Fuzz tests
+
+Some of our crates include a set of fuzz tests, this will be marked by a
+directory `fuzz`. It is a good idea to run fuzz tests after each change.
+To get started with fuzz testing you'll need to install 
+[cargo-fuzz](https://github.com/rust-fuzz/cargo-fuzz).
+
+`cargo install cargo-fuzz`
+
+To list the available fuzzing harnesses you can run;
+
+```bash
+$ cd tokio
+$ cargo fuzz list
+fuzz_linked_list
+````
+
+Running a fuzz test is as simple as;
+
+`cargo fuzz run fuzz_linked_list`
+
+**NOTE**: Keep in mind that by default when running a fuzz test the fuzz
+harness will run forever and will only exit if you `ctrl-c` or it finds
+a bug.
+
 #### Documentation tests
 
 Ideally, every API has at least one [documentation test] that demonstrates how to
diff --git a/LICENSE b/LICENSE
index 8af5baf01ea..8bdf6bd60d3 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2022 Tokio Contributors
+Copyright (c) 2023 Tokio Contributors
 
 Permission is hereby granted, free of charge, to any
 person obtaining a copy of this software and associated
diff --git a/README.md b/README.md
index 1cb160d30dc..462e6e8b0b7 100644
--- a/README.md
+++ b/README.md
@@ -56,7 +56,7 @@ Make sure you activated the full features of the tokio crate on Cargo.toml:
 
 ```toml
 [dependencies]
-tokio = { version = "1.22.0", features = ["full"] }
+tokio = { version = "1.25.0", features = ["full"] }
 ```
 Then, on your main.rs:
 
diff --git a/benches/Cargo.toml b/benches/Cargo.toml
index 78e80fb1d3c..10c32de0f3f 100644
--- a/benches/Cargo.toml
+++ b/benches/Cargo.toml
@@ -27,6 +27,16 @@ name = "sync_mpsc"
 path = "sync_mpsc.rs"
 harness = false
 
+[[bench]]
+name = "sync_mpsc_oneshot"
+path = "sync_mpsc_oneshot.rs"
+harness = false
+
+[[bench]]
+name = "sync_watch"
+path = "sync_watch.rs"
+harness = false
+
 [[bench]]
 name = "rt_multi_threaded"
 path = "rt_multi_threaded.rs"
diff --git a/benches/sync_mpsc_oneshot.rs b/benches/sync_mpsc_oneshot.rs
new file mode 100644
index 00000000000..04b783b9d41
--- /dev/null
+++ b/benches/sync_mpsc_oneshot.rs
@@ -0,0 +1,53 @@
+use bencher::{benchmark_group, benchmark_main, Bencher};
+use tokio::{
+    runtime::Runtime,
+    sync::{mpsc, oneshot},
+};
+
+fn request_reply_current_thread(b: &mut Bencher) {
+    let rt = tokio::runtime::Builder::new_current_thread()
+        .build()
+        .unwrap();
+
+    request_reply(b, rt);
+}
+
+fn request_reply_multi_threaded(b: &mut Bencher) {
+    let rt = tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(1)
+        .build()
+        .unwrap();
+
+    request_reply(b, rt);
+}
+
+fn request_reply(b: &mut Bencher, rt: Runtime) {
+    let tx = rt.block_on(async move {
+        let (tx, mut rx) = mpsc::channel::<oneshot::Sender<()>>(10);
+        tokio::spawn(async move {
+            while let Some(reply) = rx.recv().await {
+                reply.send(()).unwrap();
+            }
+        });
+        tx
+    });
+
+    b.iter(|| {
+        let task_tx = tx.clone();
+        rt.block_on(async move {
+            for _ in 0..1_000 {
+                let (o_tx, o_rx) = oneshot::channel();
+                task_tx.send(o_tx).await.unwrap();
+                let _ = o_rx.await;
+            }
+        })
+    });
+}
+
+benchmark_group!(
+    sync_mpsc_oneshot_group,
+    request_reply_current_thread,
+    request_reply_multi_threaded,
+);
+
+benchmark_main!(sync_mpsc_oneshot_group);
diff --git a/benches/sync_watch.rs b/benches/sync_watch.rs
new file mode 100644
index 00000000000..401f83c82e7
--- /dev/null
+++ b/benches/sync_watch.rs
@@ -0,0 +1,64 @@
+use bencher::{black_box, Bencher};
+use rand::prelude::*;
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::sync::Arc;
+use tokio::sync::{watch, Notify};
+
+fn rt() -> tokio::runtime::Runtime {
+    tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(6)
+        .build()
+        .unwrap()
+}
+
+fn do_work(rng: &mut impl RngCore) -> u32 {
+    use std::fmt::Write;
+    let mut message = String::new();
+    for i in 1..=10 {
+        let _ = write!(&mut message, " {i}={}", rng.gen::<f64>());
+    }
+    message
+        .as_bytes()
+        .iter()
+        .map(|&c| c as u32)
+        .fold(0, u32::wrapping_add)
+}
+
+fn contention_resubscribe(b: &mut Bencher) {
+    const NTASK: u64 = 1000;
+
+    let rt = rt();
+    let (snd, rcv) = watch::channel(0i32);
+    let wg = Arc::new((AtomicU64::new(0), Notify::new()));
+    for n in 0..NTASK {
+        let mut rcv = rcv.clone();
+        let wg = wg.clone();
+        let mut rng = rand::rngs::StdRng::seed_from_u64(n);
+        rt.spawn(async move {
+            while rcv.changed().await.is_ok() {
+                let _ = *rcv.borrow(); // contend on rwlock
+                let r = do_work(&mut rng);
+                let _ = black_box(r);
+                if wg.0.fetch_sub(1, Ordering::Release) == 1 {
+                    wg.1.notify_one();
+                }
+            }
+        });
+    }
+
+    b.iter(|| {
+        rt.block_on(async {
+            for _ in 0..100 {
+                assert_eq!(wg.0.fetch_add(NTASK, Ordering::Relaxed), 0);
+                let _ = snd.send(black_box(42));
+                while wg.0.load(Ordering::Acquire) > 0 {
+                    wg.1.notified().await;
+                }
+            }
+        });
+    });
+}
+
+bencher::benchmark_group!(contention, contention_resubscribe);
+
+bencher::benchmark_main!(contention);
diff --git a/examples/Cargo.toml b/examples/Cargo.toml
index b35c587b6f3..ceb2a36a18e 100644
--- a/examples/Cargo.toml
+++ b/examples/Cargo.toml
@@ -25,7 +25,7 @@ once_cell = "1.5.2"
 rand = "0.8.3"
 
 [target.'cfg(windows)'.dev-dependencies.windows-sys]
-version = "0.42.0"
+version = "0.45"
 
 [[example]]
 name = "chat"
diff --git a/tokio-macros/LICENSE b/tokio-macros/LICENSE
index a3753c034a9..12d1037fd0c 100644
--- a/tokio-macros/LICENSE
+++ b/tokio-macros/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2022 Tokio Contributors
+Copyright (c) 2023 Tokio Contributors
 
 Permission is hereby granted, free of charge, to any
 person obtaining a copy of this software and associated
diff --git a/tokio-macros/src/lib.rs b/tokio-macros/src/lib.rs
index 34041afa4c5..11bbbaec811 100644
--- a/tokio-macros/src/lib.rs
+++ b/tokio-macros/src/lib.rs
@@ -39,6 +39,13 @@ use proc_macro::TokenStream;
 /// function is called often, it is preferable to create the runtime using the
 /// runtime builder so the runtime can be reused across calls.
 ///
+/// # Non-worker async function
+///
+/// Note that the async function marked with this macro does not run as a
+/// worker. The expectation is that other tasks are spawned by the function here.
+/// Awaiting on other futures from the function provided here will not
+/// perform as fast as those spawned as workers.
+///
 /// # Multi-threaded runtime
 ///
 /// To use the multi-threaded runtime, the macro can be configured using
diff --git a/tokio-macros/src/select.rs b/tokio-macros/src/select.rs
index 23e280a1056..8c5ae306e67 100644
--- a/tokio-macros/src/select.rs
+++ b/tokio-macros/src/select.rs
@@ -100,10 +100,10 @@ fn clean_pattern(pat: &mut syn::Pat) {
         }
         syn::Pat::Reference(reference) => {
             reference.mutability = None;
-            clean_pattern(&mut *reference.pat);
+            clean_pattern(&mut reference.pat);
         }
         syn::Pat::Type(type_pat) => {
-            clean_pattern(&mut *type_pat.pat);
+            clean_pattern(&mut type_pat.pat);
         }
         _ => {}
     }
diff --git a/tokio-stream/CHANGELOG.md b/tokio-stream/CHANGELOG.md
index 05c2b18812c..3c9bbc3b330 100644
--- a/tokio-stream/CHANGELOG.md
+++ b/tokio-stream/CHANGELOG.md
@@ -1,3 +1,13 @@
+# 0.1.12 (January 20, 2023)
+
+- time: remove `Unpin` bound on `Throttle` methods ([#5105])
+- time: document that `throttle` operates on ms granularity ([#5101])
+- sync: add `WatchStream::from_changes` ([#5432])
+
+[#5105]: https://github.com/tokio-rs/tokio/pull/5105
+[#5101]: https://github.com/tokio-rs/tokio/pull/5101
+[#5432]: https://github.com/tokio-rs/tokio/pull/5432
+
 # 0.1.11 (October 11, 2022)
 
 - time: allow `StreamExt::chunks_timeout` outside of a runtime ([#5036])
diff --git a/tokio-stream/Cargo.toml b/tokio-stream/Cargo.toml
index 6dfa9784f79..f87b59a3654 100644
--- a/tokio-stream/Cargo.toml
+++ b/tokio-stream/Cargo.toml
@@ -4,7 +4,7 @@ name = "tokio-stream"
 # - Remove path dependencies
 # - Update CHANGELOG.md.
 # - Create "tokio-stream-0.1.x" git tag.
-version = "0.1.11"
+version = "0.1.12"
 edition = "2018"
 rust-version = "1.49"
 authors = ["Tokio Contributors <team@tokio.rs>"]
@@ -38,9 +38,6 @@ parking_lot = "0.12.0"
 tokio-test = { path = "../tokio-test" }
 futures = { version = "0.3", default-features = false }
 
-[target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
-proptest = "1"
-
 [package.metadata.docs.rs]
 all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
diff --git a/tokio-stream/LICENSE b/tokio-stream/LICENSE
index 8af5baf01ea..8bdf6bd60d3 100644
--- a/tokio-stream/LICENSE
+++ b/tokio-stream/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2022 Tokio Contributors
+Copyright (c) 2023 Tokio Contributors
 
 Permission is hereby granted, free of charge, to any
 person obtaining a copy of this software and associated
diff --git a/tokio-stream/fuzz/.gitignore b/tokio-stream/fuzz/.gitignore
new file mode 100644
index 00000000000..1a45eee7760
--- /dev/null
+++ b/tokio-stream/fuzz/.gitignore
@@ -0,0 +1,4 @@
+target
+corpus
+artifacts
+coverage
diff --git a/tokio-stream/fuzz/Cargo.toml b/tokio-stream/fuzz/Cargo.toml
new file mode 100644
index 00000000000..e1003ee5783
--- /dev/null
+++ b/tokio-stream/fuzz/Cargo.toml
@@ -0,0 +1,29 @@
+[package]
+name = "tokio-stream-fuzz"
+version = "0.0.0"
+publish = false
+edition = "2018"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+libfuzzer-sys = "0.4"
+tokio-test = { path = "../../tokio-test" }
+
+[dependencies.tokio-stream]
+path = ".."
+
+
+# Prevent this from interfering with workspaces
+[workspace]
+members = ["."]
+
+[profile.release]
+debug = 1
+
+[[bin]]
+name = "fuzz_stream_map"
+path = "fuzz_targets/fuzz_stream_map.rs"
+test = false
+doc = false
diff --git a/tokio-stream/fuzz/fuzz_targets/fuzz_stream_map.rs b/tokio-stream/fuzz/fuzz_targets/fuzz_stream_map.rs
new file mode 100644
index 00000000000..4c3a2d04aaf
--- /dev/null
+++ b/tokio-stream/fuzz/fuzz_targets/fuzz_stream_map.rs
@@ -0,0 +1,80 @@
+#![no_main]
+
+use libfuzzer_sys::fuzz_target;
+use std::pin::Pin;
+
+use tokio_stream::{self as stream, pending, Stream, StreamExt, StreamMap};
+use tokio_test::{assert_ok, assert_pending, assert_ready, task};
+
+macro_rules! assert_ready_some {
+    ($($t:tt)*) => {
+        match assert_ready!($($t)*) {
+            Some(v) => v,
+            None => panic!("expected `Some`, got `None`"),
+        }
+    };
+}
+
+macro_rules! assert_ready_none {
+    ($($t:tt)*) => {
+        match assert_ready!($($t)*) {
+            None => {}
+            Some(v) => panic!("expected `None`, got `Some({:?})`", v),
+        }
+    };
+}
+
+fn pin_box<T: Stream<Item = U> + 'static, U>(s: T) -> Pin<Box<dyn Stream<Item = U>>> {
+    Box::pin(s)
+}
+
+fuzz_target!(|data: &[u8]| {
+    use std::task::{Context, Poll};
+
+    struct DidPoll<T> {
+        did_poll: bool,
+        inner: T,
+    }
+
+    impl<T: Stream + Unpin> Stream for DidPoll<T> {
+        type Item = T::Item;
+
+        fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T::Item>> {
+            self.did_poll = true;
+            Pin::new(&mut self.inner).poll_next(cx)
+        }
+    }
+
+    for _ in 0..10 {
+        let mut map = task::spawn(StreamMap::new());
+        let mut expect = 0;
+
+        for (i, is_empty) in data.iter().map(|x| *x != 0).enumerate() {
+            let inner = if is_empty {
+                pin_box(stream::empty::<()>())
+            } else {
+                expect += 1;
+                pin_box(stream::pending::<()>())
+            };
+
+            let stream = DidPoll {
+                did_poll: false,
+                inner,
+            };
+
+            map.insert(i, stream);
+        }
+
+        if expect == 0 {
+            assert_ready_none!(map.poll_next());
+        } else {
+            assert_pending!(map.poll_next());
+
+            assert_eq!(expect, map.values().count());
+
+            for stream in map.values() {
+                assert!(stream.did_poll);
+            }
+        }
+    }
+});
diff --git a/tokio-stream/src/stream_ext/then.rs b/tokio-stream/src/stream_ext/then.rs
index 7f6b5a2394f..cc7caa721e0 100644
--- a/tokio-stream/src/stream_ext/then.rs
+++ b/tokio-stream/src/stream_ext/then.rs
@@ -72,7 +72,7 @@ where
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
-        let future_len = if self.future.is_some() { 1 } else { 0 };
+        let future_len = usize::from(self.future.is_some());
         let (lower, upper) = self.stream.size_hint();
 
         let lower = lower.saturating_add(future_len);
diff --git a/tokio-stream/src/wrappers/watch.rs b/tokio-stream/src/wrappers/watch.rs
index c682c9c271d..ec8ead06da0 100644
--- a/tokio-stream/src/wrappers/watch.rs
+++ b/tokio-stream/src/wrappers/watch.rs
@@ -10,8 +10,9 @@ use tokio::sync::watch::error::RecvError;
 
 /// A wrapper around [`tokio::sync::watch::Receiver`] that implements [`Stream`].
 ///
-/// This stream will always start by yielding the current value when the WatchStream is polled,
-/// regardless of whether it was the initial value or sent afterwards.
+/// This stream will start by yielding the current value when the WatchStream is polled,
+/// regardless of whether it was the initial value or sent afterwards,
+/// unless you use [`WatchStream<T>::from_changes`].
 ///
 /// # Examples
 ///
@@ -40,6 +41,28 @@ use tokio::sync::watch::error::RecvError;
 /// let (tx, rx) = watch::channel("hello");
 /// let mut rx = WatchStream::new(rx);
 ///
+/// // existing rx output with "hello" is ignored here
+///
+/// tx.send("goodbye").unwrap();
+/// assert_eq!(rx.next().await, Some("goodbye"));
+/// # }
+/// ```
+///
+/// Example with [`WatchStream<T>::from_changes`]:
+///
+/// ```
+/// # #[tokio::main]
+/// # async fn main() {
+/// use futures::future::FutureExt;
+/// use tokio::sync::watch;
+/// use tokio_stream::{StreamExt, wrappers::WatchStream};
+///
+/// let (tx, rx) = watch::channel("hello");
+/// let mut rx = WatchStream::from_changes(rx);
+///
+/// // no output from rx is available at this point - let's check this:
+/// assert!(rx.next().now_or_never().is_none());
+///
 /// tx.send("goodbye").unwrap();
 /// assert_eq!(rx.next().await, Some("goodbye"));
 /// # }
@@ -66,6 +89,13 @@ impl<T: 'static + Clone + Send + Sync> WatchStream<T> {
             inner: ReusableBoxFuture::new(async move { (Ok(()), rx) }),
         }
     }
+
+    /// Create a new `WatchStream` that waits for the value to be changed.
+    pub fn from_changes(rx: Receiver<T>) -> Self {
+        Self {
+            inner: ReusableBoxFuture::new(make_future(rx)),
+        }
+    }
 }
 
 impl<T: Clone + 'static + Send + Sync> Stream for WatchStream<T> {
diff --git a/tokio-stream/tests/stream_stream_map.rs b/tokio-stream/tests/stream_stream_map.rs
index ffc489b32ef..b6b87e9d0ac 100644
--- a/tokio-stream/tests/stream_stream_map.rs
+++ b/tokio-stream/tests/stream_stream_map.rs
@@ -325,63 +325,6 @@ fn one_ready_many_none() {
     }
 }
 
-#[cfg(not(target_os = "wasi"))]
-proptest::proptest! {
-    #[test]
-    fn fuzz_pending_complete_mix(kinds: Vec<bool>) {
-        use std::task::{Context, Poll};
-
-        struct DidPoll<T> {
-            did_poll: bool,
-            inner: T,
-        }
-
-        impl<T: Stream + Unpin> Stream for DidPoll<T> {
-            type Item = T::Item;
-
-            fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>)
-                -> Poll<Option<T::Item>>
-            {
-                self.did_poll = true;
-                Pin::new(&mut self.inner).poll_next(cx)
-            }
-        }
-
-        for _ in 0..10 {
-            let mut map = task::spawn(StreamMap::new());
-            let mut expect = 0;
-
-            for (i, &is_empty) in kinds.iter().enumerate() {
-                let inner = if is_empty {
-                    pin_box(stream::empty::<()>())
-                } else {
-                    expect += 1;
-                    pin_box(stream::pending::<()>())
-                };
-
-                let stream = DidPoll {
-                    did_poll: false,
-                    inner,
-                };
-
-                map.insert(i, stream);
-            }
-
-            if expect == 0 {
-                assert_ready_none!(map.poll_next());
-            } else {
-                assert_pending!(map.poll_next());
-
-                assert_eq!(expect, map.values().count());
-
-                for stream in map.values() {
-                    assert!(stream.did_poll);
-                }
-            }
-        }
-    }
-}
-
 fn pin_box<T: Stream<Item = U> + 'static, U>(s: T) -> Pin<Box<dyn Stream<Item = U>>> {
     Box::pin(s)
 }
diff --git a/tokio-stream/tests/watch.rs b/tokio-stream/tests/watch.rs
index a56254edefd..3a39aaf3db7 100644
--- a/tokio-stream/tests/watch.rs
+++ b/tokio-stream/tests/watch.rs
@@ -3,9 +3,11 @@
 use tokio::sync::watch;
 use tokio_stream::wrappers::WatchStream;
 use tokio_stream::StreamExt;
+use tokio_test::assert_pending;
+use tokio_test::task::spawn;
 
 #[tokio::test]
-async fn message_not_twice() {
+async fn watch_stream_message_not_twice() {
     let (tx, rx) = watch::channel("hello");
 
     let mut counter = 0;
@@ -27,3 +29,29 @@ async fn message_not_twice() {
     drop(tx);
     task.await.unwrap();
 }
+
+#[tokio::test]
+async fn watch_stream_from_rx() {
+    let (tx, rx) = watch::channel("hello");
+
+    let mut stream = WatchStream::from(rx);
+
+    assert_eq!(stream.next().await.unwrap(), "hello");
+
+    tx.send("bye").unwrap();
+
+    assert_eq!(stream.next().await.unwrap(), "bye");
+}
+
+#[tokio::test]
+async fn watch_stream_from_changes() {
+    let (tx, rx) = watch::channel("hello");
+
+    let mut stream = WatchStream::from_changes(rx);
+
+    assert_pending!(spawn(&mut stream).poll_next());
+
+    tx.send("bye").unwrap();
+
+    assert_eq!(stream.next().await.unwrap(), "bye");
+}
diff --git a/tokio-test/Cargo.toml b/tokio-test/Cargo.toml
index e889dcec85a..30cacead51f 100644
--- a/tokio-test/Cargo.toml
+++ b/tokio-test/Cargo.toml
@@ -19,7 +19,7 @@ categories = ["asynchronous", "testing"]
 [dependencies]
 tokio = { version = "1.2.0", path = "../tokio", features = ["rt", "sync", "time", "test-util"] }
 tokio-stream = { version = "0.1.1", path = "../tokio-stream" }
-async-stream = "0.3"
+async-stream = "0.3.3"
 
 bytes = "1.0.0"
 futures-core = "0.3.0"
diff --git a/tokio-test/LICENSE b/tokio-test/LICENSE
index 8af5baf01ea..8bdf6bd60d3 100644
--- a/tokio-test/LICENSE
+++ b/tokio-test/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2022 Tokio Contributors
+Copyright (c) 2023 Tokio Contributors
 
 Permission is hereby granted, free of charge, to any
 person obtaining a copy of this software and associated
diff --git a/tokio-util/CHANGELOG.md b/tokio-util/CHANGELOG.md
index ca378b1ed20..0c11b2144eb 100644
--- a/tokio-util/CHANGELOG.md
+++ b/tokio-util/CHANGELOG.md
@@ -1,3 +1,52 @@
+# 0.7.7 (February 12, 2023)
+
+This release reverts the removal of the `Encoder` bound on the `FramedParts`
+constructor from [#5280] since it turned out to be a breaking change. ([#5450])
+
+[#5450]: https://github.com/tokio-rs/tokio/pull/5450
+
+# 0.7.6 (February 10, 2023)
+
+This release fixes a compilation failure in 0.7.5 when it is used together with
+Tokio version 1.21 and unstable features are enabled. ([#5445])
+
+[#5445]: https://github.com/tokio-rs/tokio/pull/5445
+
+# 0.7.5 (February 9, 2023)
+
+This release fixes an accidental breaking change where `UnwindSafe` was
+accidentally removed from `CancellationToken`.
+
+### Added
+- codec: add `Framed::backpressure_boundary` ([#5124])
+- io: add `InspectReader` and `InspectWriter` ([#5033])
+- io: add `tokio_util::io::{CopyToBytes, SinkWriter}` ([#5070], [#5436])
+- io: impl `std::io::BufRead` on `SyncIoBridge` ([#5265])
+- sync: add `PollSemaphore::poll_acquire_many` ([#5137])
+- sync: add owned future for `CancellationToken` ([#5153])
+- time: add `DelayQueue::try_remove` ([#5052])
+
+### Fixed
+- codec: fix `LengthDelimitedCodec` buffer over-reservation ([#4997])
+- sync: impl `UnwindSafe` on `CancellationToken` ([#5438])
+- util: remove `Encoder` bound on `FramedParts` constructor ([#5280])
+
+### Documented
+- io: add lines example for `StreamReader` ([#5145])
+
+[#4997]: https://github.com/tokio-rs/tokio/pull/4997
+[#5033]: https://github.com/tokio-rs/tokio/pull/5033
+[#5052]: https://github.com/tokio-rs/tokio/pull/5052
+[#5070]: https://github.com/tokio-rs/tokio/pull/5070
+[#5124]: https://github.com/tokio-rs/tokio/pull/5124
+[#5137]: https://github.com/tokio-rs/tokio/pull/5137
+[#5145]: https://github.com/tokio-rs/tokio/pull/5145
+[#5153]: https://github.com/tokio-rs/tokio/pull/5153
+[#5265]: https://github.com/tokio-rs/tokio/pull/5265
+[#5280]: https://github.com/tokio-rs/tokio/pull/5280
+[#5436]: https://github.com/tokio-rs/tokio/pull/5436
+[#5438]: https://github.com/tokio-rs/tokio/pull/5438
+
 # 0.7.4 (September 8, 2022)
 
 ### Added
diff --git a/tokio-util/Cargo.toml b/tokio-util/Cargo.toml
index d5a9f748c18..267662b4d5b 100644
--- a/tokio-util/Cargo.toml
+++ b/tokio-util/Cargo.toml
@@ -4,7 +4,7 @@ name = "tokio-util"
 # - Remove path dependencies
 # - Update CHANGELOG.md.
 # - Create "tokio-util-0.7.x" git tag.
-version = "0.7.4"
+version = "0.7.7"
 edition = "2018"
 rust-version = "1.49"
 authors = ["Tokio Contributors <team@tokio.rs>"]
@@ -34,7 +34,7 @@ rt = ["tokio/rt", "tokio/sync", "futures-util", "hashbrown"]
 __docs_rs = ["futures-util"]
 
 [dependencies]
-tokio = { version = "1.21.0", path = "../tokio", features = ["sync"] }
+tokio = { version = "1.22.0", path = "../tokio", features = ["sync"] }
 bytes = "1.0.0"
 futures-core = "0.3.0"
 futures-sink = "0.3.0"
diff --git a/tokio-util/LICENSE b/tokio-util/LICENSE
index 8af5baf01ea..8bdf6bd60d3 100644
--- a/tokio-util/LICENSE
+++ b/tokio-util/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2022 Tokio Contributors
+Copyright (c) 2023 Tokio Contributors
 
 Permission is hereby granted, free of charge, to any
 person obtaining a copy of this software and associated
diff --git a/tokio-util/src/io/sink_writer.rs b/tokio-util/src/io/sink_writer.rs
index 5d1acc499cc..f2af262c4d0 100644
--- a/tokio-util/src/io/sink_writer.rs
+++ b/tokio-util/src/io/sink_writer.rs
@@ -1,3 +1,4 @@
+use futures_core::ready;
 use futures_sink::Sink;
 
 use pin_project_lite::pin_project;
@@ -98,19 +99,11 @@ where
         buf: &[u8],
     ) -> Poll<Result<usize, io::Error>> {
         let mut this = self.project();
-        match this.inner.as_mut().poll_ready(cx) {
-            Poll::Ready(Ok(())) => {
-                if let Err(e) = this.inner.as_mut().start_send(buf) {
-                    Poll::Ready(Err(e.into()))
-                } else {
-                    Poll::Ready(Ok(buf.len()))
-                }
-            }
-            Poll::Ready(Err(e)) => Poll::Ready(Err(e.into())),
-            Poll::Pending => {
-                cx.waker().wake_by_ref();
-                Poll::Pending
-            }
+
+        ready!(this.inner.as_mut().poll_ready(cx).map_err(Into::into))?;
+        match this.inner.as_mut().start_send(buf) {
+            Ok(()) => Poll::Ready(Ok(buf.len())),
+            Err(e) => Poll::Ready(Err(e.into())),
         }
     }
 
diff --git a/tokio-util/src/io/sync_bridge.rs b/tokio-util/src/io/sync_bridge.rs
index 5682258c3b3..f87bfbb9c4e 100644
--- a/tokio-util/src/io/sync_bridge.rs
+++ b/tokio-util/src/io/sync_bridge.rs
@@ -1,5 +1,7 @@
-use std::io::{Read, Write};
-use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
+use std::io::{BufRead, Read, Write};
+use tokio::io::{
+    AsyncBufRead, AsyncBufReadExt, AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt,
+};
 
 /// Use a [`tokio::io::AsyncRead`] synchronously as a [`std::io::Read`] or
 /// a [`tokio::io::AsyncWrite`] as a [`std::io::Write`].
@@ -9,6 +11,28 @@ pub struct SyncIoBridge<T> {
     rt: tokio::runtime::Handle,
 }
 
+impl<T: AsyncBufRead + Unpin> BufRead for SyncIoBridge<T> {
+    fn fill_buf(&mut self) -> std::io::Result<&[u8]> {
+        let src = &mut self.src;
+        self.rt.block_on(AsyncBufReadExt::fill_buf(src))
+    }
+
+    fn consume(&mut self, amt: usize) {
+        let src = &mut self.src;
+        AsyncBufReadExt::consume(src, amt)
+    }
+
+    fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> std::io::Result<usize> {
+        let src = &mut self.src;
+        self.rt
+            .block_on(AsyncBufReadExt::read_until(src, byte, buf))
+    }
+    fn read_line(&mut self, buf: &mut String) -> std::io::Result<usize> {
+        let src = &mut self.src;
+        self.rt.block_on(AsyncBufReadExt::read_line(src, buf))
+    }
+}
+
 impl<T: AsyncRead + Unpin> Read for SyncIoBridge<T> {
     fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
         let src = &mut self.src;
diff --git a/tokio-util/src/sync/cancellation_token.rs b/tokio-util/src/sync/cancellation_token.rs
index fbceb2eeba2..c44be69864f 100644
--- a/tokio-util/src/sync/cancellation_token.rs
+++ b/tokio-util/src/sync/cancellation_token.rs
@@ -55,6 +55,9 @@ pub struct CancellationToken {
     inner: Arc<tree_node::TreeNode>,
 }
 
+impl std::panic::UnwindSafe for CancellationToken {}
+impl std::panic::RefUnwindSafe for CancellationToken {}
+
 pin_project! {
     /// A Future that is resolved once the corresponding [`CancellationToken`]
     /// is cancelled.
diff --git a/tokio-util/src/sync/poll_semaphore.rs b/tokio-util/src/sync/poll_semaphore.rs
index 85f75a40896..6b44574a161 100644
--- a/tokio-util/src/sync/poll_semaphore.rs
+++ b/tokio-util/src/sync/poll_semaphore.rs
@@ -166,6 +166,6 @@ impl fmt::Debug for PollSemaphore {
 
 impl AsRef<Semaphore> for PollSemaphore {
     fn as_ref(&self) -> &Semaphore {
-        &*self.semaphore
+        &self.semaphore
     }
 }
diff --git a/tokio-util/tests/spawn_pinned.rs b/tokio-util/tests/spawn_pinned.rs
index b620cce048c..9ea8cd27830 100644
--- a/tokio-util/tests/spawn_pinned.rs
+++ b/tokio-util/tests/spawn_pinned.rs
@@ -82,8 +82,8 @@ async fn task_panic_propagates() {
     assert!(result.is_err());
     let error = result.unwrap_err();
     assert!(error.is_panic());
-    let panic_str: &str = *error.into_panic().downcast().unwrap();
-    assert_eq!(panic_str, "Test panic");
+    let panic_str = error.into_panic().downcast::<&'static str>().unwrap();
+    assert_eq!(*panic_str, "Test panic");
 
     // Trying again with a "safe" task still works
     let join_handle = pool.spawn_pinned(|| async { "test" });
@@ -108,8 +108,8 @@ async fn callback_panic_does_not_kill_worker() {
     assert!(result.is_err());
     let error = result.unwrap_err();
     assert!(error.is_panic());
-    let panic_str: &str = *error.into_panic().downcast().unwrap();
-    assert_eq!(panic_str, "Test panic");
+    let panic_str = error.into_panic().downcast::<&'static str>().unwrap();
+    assert_eq!(*panic_str, "Test panic");
 
     // Trying again with a "safe" callback works
     let join_handle = pool.spawn_pinned(|| async { "test" });
diff --git a/tokio-util/tests/time_delay_queue.rs b/tokio-util/tests/time_delay_queue.rs
index 0fcdbf4a073..9ceae34365c 100644
--- a/tokio-util/tests/time_delay_queue.rs
+++ b/tokio-util/tests/time_delay_queue.rs
@@ -1,4 +1,4 @@
-#![allow(clippy::blacklisted_name)]
+#![allow(clippy::disallowed_names)]
 #![warn(rust_2018_idioms)]
 #![cfg(feature = "full")]
 
diff --git a/tokio/CHANGELOG.md b/tokio/CHANGELOG.md
index 670289d0913..39a57fde717 100644
--- a/tokio/CHANGELOG.md
+++ b/tokio/CHANGELOG.md
@@ -1,3 +1,95 @@
+# 1.25.0 (January 28, 2023)
+
+### Fixed
+
+- rt: fix runtime metrics reporting ([#5330])
+
+### Added
+
+- sync: add `broadcast::Sender::len` ([#5343])
+
+### Changed
+
+- fs: increase maximum read buffer size to 2MiB ([#5397])
+
+[#5330]: https://github.com/tokio-rs/tokio/pull/5330
+[#5343]: https://github.com/tokio-rs/tokio/pull/5343
+[#5397]: https://github.com/tokio-rs/tokio/pull/5397
+
+# 1.24.2 (January 17, 2023)
+
+Forward ports 1.18.5 changes.
+
+### Fixed
+
+- io: fix unsoundness in `ReadHalf::unsplit` ([#5375])
+
+[#5375]: https://github.com/tokio-rs/tokio/pull/5375
+
+# 1.24.1 (January 6, 2022)
+
+This release fixes a compilation failure on targets without `AtomicU64` when using rustc older than 1.63. ([#5356])
+
+[#5356]: https://github.com/tokio-rs/tokio/pull/5356
+
+# 1.24.0 (January 5, 2022)
+
+### Fixed
+ - rt: improve native `AtomicU64` support detection ([#5284])
+
+### Added
+ - rt: add configuration option for max number of I/O events polled from the OS
+   per tick ([#5186])
+ - rt: add an environment variable for configuring the default number of worker
+   threads per runtime instance ([#4250])
+
+### Changed
+ - sync: reduce MPSC channel stack usage ([#5294])
+ - io: reduce lock contention in I/O operations  ([#5300])
+ - fs: speed up `read_dir()` by chunking operations ([#5309])
+ - rt: use internal `ThreadId` implementation ([#5329])
+ - test: don't auto-advance time when a `spawn_blocking` task is running ([#5115])
+
+[#5186]: https://github.com/tokio-rs/tokio/pull/5186
+[#5294]: https://github.com/tokio-rs/tokio/pull/5294
+[#5284]: https://github.com/tokio-rs/tokio/pull/5284
+[#4250]: https://github.com/tokio-rs/tokio/pull/4250
+[#5300]: https://github.com/tokio-rs/tokio/pull/5300
+[#5329]: https://github.com/tokio-rs/tokio/pull/5329
+[#5115]: https://github.com/tokio-rs/tokio/pull/5115
+[#5309]: https://github.com/tokio-rs/tokio/pull/5309
+
+# 1.23.1 (January 4, 2022)
+
+This release forward ports changes from 1.18.4.
+
+### Fixed
+
+- net: fix Windows named pipe server builder to maintain option when toggling
+  pipe mode ([#5336]).
+
+[#5336]: https://github.com/tokio-rs/tokio/pull/5336
+
+# 1.23.0 (December 5, 2022)
+
+### Fixed
+
+ - net: fix Windows named pipe connect ([#5208])
+ - io: support vectored writes for `ChildStdin` ([#5216])
+ - io: fix `async fn ready()` false positive for OS-specific events ([#5231])
+
+ ### Changed
+ - runtime: `yield_now` defers task until after driver poll ([#5223])
+ - runtime: reduce amount of codegen needed per spawned task ([#5213])
+ - windows: replace `winapi` dependency with `windows-sys` ([#5204])
+
+ [#5208]: https://github.com/tokio-rs/tokio/pull/5208
+ [#5216]: https://github.com/tokio-rs/tokio/pull/5216
+ [#5213]: https://github.com/tokio-rs/tokio/pull/5213
+ [#5204]: https://github.com/tokio-rs/tokio/pull/5204
+ [#5223]: https://github.com/tokio-rs/tokio/pull/5223
+ [#5231]: https://github.com/tokio-rs/tokio/pull/5231
+
 # 1.22.0 (November 17, 2022)
 
 ### Added
@@ -242,6 +334,27 @@ wasm32-wasi target is given unstable support for the `net` feature.
 [#4956]: https://github.com/tokio-rs/tokio/pull/4956
 [#4959]: https://github.com/tokio-rs/tokio/pull/4959
 
+# 1.20.4 (January 17, 2023)
+
+Forward ports 1.18.5 changes.
+
+### Fixed
+
+- io: fix unsoundness in `ReadHalf::unsplit` ([#5375])
+
+[#5375]: https://github.com/tokio-rs/tokio/pull/5375
+
+# 1.20.3 (January 3, 2022)
+
+This release forward ports changes from 1.18.4.
+
+### Fixed
+
+- net: fix Windows named pipe server builder to maintain option when toggling
+  pipe mode ([#5336]).
+
+[#5336]: https://github.com/tokio-rs/tokio/pull/5336
+
 # 1.20.2 (September 27, 2022)
 
 This release removes the dependency on the `once_cell` crate to restore the MSRV
@@ -367,6 +480,23 @@ This release fixes a bug in `Notified::enable`. ([#4747])
 [#4729]: https://github.com/tokio-rs/tokio/pull/4729
 [#4739]: https://github.com/tokio-rs/tokio/pull/4739
 
+# 1.18.5 (January 17, 2023)
+
+### Fixed
+
+- io: fix unsoundness in `ReadHalf::unsplit` ([#5375])
+
+[#5375]: https://github.com/tokio-rs/tokio/pull/5375
+
+# 1.18.4 (January 3, 2022)
+
+### Fixed
+
+- net: fix Windows named pipe server builder to maintain option when toggling
+  pipe mode ([#5336]).
+
+[#5336]: https://github.com/tokio-rs/tokio/pull/5336
+
 # 1.18.3 (September 27, 2022)
 
 This release removes the dependency on the `once_cell` crate to restore the MSRV
@@ -494,7 +624,7 @@ performance improvements.
 - time: use bit manipulation instead of modulo to improve performance ([#4480])
 - net: use `std::future::Ready` instead of our own `Ready` future ([#4271])
 - replace deprecated `atomic::spin_loop_hint` with `hint::spin_loop` ([#4491])
-- fix miri failures in intrusive linked lists ([#4397]) 
+- fix miri failures in intrusive linked lists ([#4397])
 
 ### Documented
 
diff --git a/tokio/Cargo.toml b/tokio/Cargo.toml
index efa6ddc95ef..3087c3318e5 100644
--- a/tokio/Cargo.toml
+++ b/tokio/Cargo.toml
@@ -6,7 +6,7 @@ name = "tokio"
 #   - README.md
 # - Update CHANGELOG.md.
 # - Create "v1.x.y" git tag.
-version = "1.22.0"
+version = "1.25.0"
 edition = "2018"
 rust-version = "1.49"
 authors = ["Tokio Contributors <team@tokio.rs>"]
@@ -122,14 +122,14 @@ signal-hook-registry = { version = "1.1.1", optional = true }
 
 [target.'cfg(unix)'.dev-dependencies]
 libc = { version = "0.2.42" }
-nix = { version = "0.24", default-features = false, features = ["fs", "socket"] }
+nix = { version = "0.26", default-features = false, features = ["fs", "socket"] }
 
 [target.'cfg(windows)'.dependencies.windows-sys]
-version = "0.42.0"
+version = "0.45"
 optional = true
 
 [target.'cfg(docsrs)'.dependencies.windows-sys]
-version = "0.42.0"
+version = "0.45"
 features = [
     "Win32_Foundation",
     "Win32_Security_Authorization",
@@ -143,12 +143,11 @@ tokio-test = { version = "0.4.0", path = "../tokio-test" }
 tokio-stream = { version = "0.1", path = "../tokio-stream" }
 futures = { version = "0.3.0", features = ["async-await"] }
 mockall = "0.11.1"
-tempfile = "3.1.0"
 async-stream = "0.3"
 
 [target.'cfg(not(any(target_arch = "wasm32", target_arch = "wasm64")))'.dev-dependencies]
-proptest = "1"
 socket2 = "0.4"
+tempfile = "3.1.0"
 
 [target.'cfg(not(all(any(target_arch = "wasm32", target_arch = "wasm64"), target_os = "unknown")))'.dev-dependencies]
 rand = "0.8.0"
@@ -157,7 +156,7 @@ rand = "0.8.0"
 wasm-bindgen-test = "0.3.0"
 
 [target.'cfg(target_os = "freebsd")'.dev-dependencies]
-mio-aio = { version = "0.6.0", features = ["tokio"] }
+mio-aio = { version = "0.7.0", features = ["tokio"] }
 
 [target.'cfg(loom)'.dev-dependencies]
 loom = { version = "0.5.2", features = ["futures", "checkpoint"] }
diff --git a/tokio/LICENSE b/tokio/LICENSE
index 8af5baf01ea..8bdf6bd60d3 100644
--- a/tokio/LICENSE
+++ b/tokio/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2022 Tokio Contributors
+Copyright (c) 2023 Tokio Contributors
 
 Permission is hereby granted, free of charge, to any
 person obtaining a copy of this software and associated
diff --git a/tokio/README.md b/tokio/README.md
index 1cb160d30dc..462e6e8b0b7 100644
--- a/tokio/README.md
+++ b/tokio/README.md
@@ -56,7 +56,7 @@ Make sure you activated the full features of the tokio crate on Cargo.toml:
 
 ```toml
 [dependencies]
-tokio = { version = "1.22.0", features = ["full"] }
+tokio = { version = "1.25.0", features = ["full"] }
 ```
 Then, on your main.rs:
 
diff --git a/tokio/build.rs b/tokio/build.rs
index 93b05092bf9..ddade2876bb 100644
--- a/tokio/build.rs
+++ b/tokio/build.rs
@@ -24,10 +24,26 @@ const CONST_MUTEX_NEW_PROBE: &str = r#"
 }
 "#;
 
+const TARGET_HAS_ATOMIC_PROBE: &str = r#"
+{
+    #[cfg(target_has_atomic = "ptr")]
+    let _ = ();
+}
+"#;
+
+const TARGET_ATOMIC_U64_PROBE: &str = r#"
+{
+    #[allow(unused_imports)]
+    use std::sync::atomic::AtomicU64 as _;
+}
+"#;
+
 fn main() {
     let mut enable_const_thread_local = false;
     let mut enable_addr_of = false;
+    let mut enable_target_has_atomic = false;
     let mut enable_const_mutex_new = false;
+    let mut target_needs_atomic_u64_fallback = false;
 
     match AutoCfg::new() {
         Ok(ac) => {
@@ -66,6 +82,27 @@ fn main() {
                 }
             }
 
+            // The `target_has_atomic` cfg was stabilized in 1.60.
+            if ac.probe_rustc_version(1, 61) {
+                enable_target_has_atomic = true;
+            } else if ac.probe_rustc_version(1, 60) {
+                // This compiler claims to be 1.60, but there are some nightly
+                // compilers that claim to be 1.60 without supporting the
+                // feature. Explicitly probe to check if code using them
+                // compiles.
+                //
+                // The oldest nightly that supports the feature is 2022-02-11.
+                if ac.probe_expression(TARGET_HAS_ATOMIC_PROBE) {
+                    enable_target_has_atomic = true;
+                }
+            }
+
+            // If we can't tell using `target_has_atomic`, tell if the target
+            // has `AtomicU64` by trying to use it.
+            if !enable_target_has_atomic && !ac.probe_expression(TARGET_ATOMIC_U64_PROBE) {
+                target_needs_atomic_u64_fallback = true;
+            }
+
             // The `Mutex::new` method was made const in 1.63.
             if ac.probe_rustc_version(1, 64) {
                 enable_const_mutex_new = true;
@@ -109,6 +146,14 @@ fn main() {
         autocfg::emit("tokio_no_addr_of")
     }
 
+    if !enable_target_has_atomic {
+        // To disable this feature on compilers that support it, you can
+        // explicitly pass this flag with the following environment variable:
+        //
+        // RUSTFLAGS="--cfg tokio_no_target_has_atomic"
+        autocfg::emit("tokio_no_target_has_atomic")
+    }
+
     if !enable_const_mutex_new {
         // To disable this feature on compilers that support it, you can
         // explicitly pass this flag with the following environment variable:
@@ -117,6 +162,14 @@ fn main() {
         autocfg::emit("tokio_no_const_mutex_new")
     }
 
+    if target_needs_atomic_u64_fallback {
+        // To disable this feature on compilers that support it, you can
+        // explicitly pass this flag with the following environment variable:
+        //
+        // RUSTFLAGS="--cfg tokio_no_atomic_u64"
+        autocfg::emit("tokio_no_atomic_u64")
+    }
+
     let target = ::std::env::var("TARGET").unwrap_or_default();
 
     // We emit cfgs instead of using `target_family = "wasm"` that requires Rust 1.54.
diff --git a/tokio/docs/reactor-refactor.md b/tokio/docs/reactor-refactor.md
index 3005afc0168..77e64f4dfd7 100644
--- a/tokio/docs/reactor-refactor.md
+++ b/tokio/docs/reactor-refactor.md
@@ -188,12 +188,12 @@ readiness, the driver's tick is packed into the atomic `usize`.
 The `ScheduledIo` readiness `AtomicUsize` is structured as:
 
 ```
-| reserved | generation |  driver tick | readiness |
+| shutdown | generation |  driver tick | readiness |
 |----------+------------+--------------+-----------|
 |   1 bit  |   7 bits   +    8 bits    +  16 bits  |
 ```
 
-The `reserved` and `generation` components exist today.
+The `shutdown` and `generation` components exist today.
 
 The `readiness()` function returns a `ReadyEvent` value. This value includes the
 `tick` component read with the resource's readiness value. When
diff --git a/tokio/fuzz/.gitignore b/tokio/fuzz/.gitignore
new file mode 100644
index 00000000000..1a45eee7760
--- /dev/null
+++ b/tokio/fuzz/.gitignore
@@ -0,0 +1,4 @@
+target
+corpus
+artifacts
+coverage
diff --git a/tokio/fuzz/Cargo.toml b/tokio/fuzz/Cargo.toml
new file mode 100644
index 00000000000..4b47d7bdf94
--- /dev/null
+++ b/tokio/fuzz/Cargo.toml
@@ -0,0 +1,29 @@
+[package]
+name = "tokio-fuzz"
+version = "0.0.0"
+publish = false
+edition = "2018"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+libfuzzer-sys = "0.4"
+
+[dependencies.tokio]
+path = ".."
+features = ["fs","net","process","rt","sync","signal","time"]
+
+
+# Prevent this from interfering with workspaces
+[workspace]
+members = ["."]
+
+[profile.release]
+debug = 1
+
+[[bin]]
+name = "fuzz_linked_list"
+path = "fuzz_targets/fuzz_linked_list.rs"
+test = false
+doc = false
diff --git a/tokio/fuzz/fuzz_targets/fuzz_linked_list.rs b/tokio/fuzz/fuzz_targets/fuzz_linked_list.rs
new file mode 100644
index 00000000000..276e16dc775
--- /dev/null
+++ b/tokio/fuzz/fuzz_targets/fuzz_linked_list.rs
@@ -0,0 +1,7 @@
+#![no_main]
+
+use libfuzzer_sys::fuzz_target;
+
+fuzz_target!(|data: &[u8]| {
+    tokio::fuzz::fuzz_linked_list(data);
+});
diff --git a/tokio/src/fs/file/tests.rs b/tokio/src/fs/file/tests.rs
index 1c90a8d1541..7c61b3c4b31 100644
--- a/tokio/src/fs/file/tests.rs
+++ b/tokio/src/fs/file/tests.rs
@@ -231,12 +231,12 @@ fn flush_while_idle() {
 #[cfg_attr(miri, ignore)] // takes a really long time with miri
 fn read_with_buffer_larger_than_max() {
     // Chunks
-    let chunk_a = 16 * 1024;
+    let chunk_a = crate::io::blocking::MAX_BUF;
     let chunk_b = chunk_a * 2;
     let chunk_c = chunk_a * 3;
     let chunk_d = chunk_a * 4;
 
-    assert_eq!(chunk_d / 1024, 64);
+    assert_eq!(chunk_d / 1024 / 1024, 8);
 
     let mut data = vec![];
     for i in 0..(chunk_d - 1) {
@@ -303,12 +303,12 @@ fn read_with_buffer_larger_than_max() {
 #[cfg_attr(miri, ignore)] // takes a really long time with miri
 fn write_with_buffer_larger_than_max() {
     // Chunks
-    let chunk_a = 16 * 1024;
+    let chunk_a = crate::io::blocking::MAX_BUF;
     let chunk_b = chunk_a * 2;
     let chunk_c = chunk_a * 3;
     let chunk_d = chunk_a * 4;
 
-    assert_eq!(chunk_d / 1024, 64);
+    assert_eq!(chunk_d / 1024 / 1024, 8);
 
     let mut data = vec![];
     for i in 0..(chunk_d - 1) {
diff --git a/tokio/src/fs/mod.rs b/tokio/src/fs/mod.rs
index 3afefc6e3fb..30ce6a91a35 100644
--- a/tokio/src/fs/mod.rs
+++ b/tokio/src/fs/mod.rs
@@ -102,6 +102,9 @@ pub use self::write::write;
 mod copy;
 pub use self::copy::copy;
 
+mod try_exists;
+pub use self::try_exists::try_exists;
+
 #[cfg(test)]
 mod mocks;
 
diff --git a/tokio/src/fs/read_dir.rs b/tokio/src/fs/read_dir.rs
index 10ad150d70c..9471e8ce809 100644
--- a/tokio/src/fs/read_dir.rs
+++ b/tokio/src/fs/read_dir.rs
@@ -1,5 +1,6 @@
 use crate::fs::asyncify;
 
+use std::collections::VecDeque;
 use std::ffi::OsString;
 use std::fs::{FileType, Metadata};
 use std::future::Future;
@@ -19,6 +20,8 @@ use crate::blocking::spawn_blocking;
 #[cfg(not(test))]
 use crate::blocking::JoinHandle;
 
+const CHUNK_SIZE: usize = 32;
+
 /// Returns a stream over the entries within a directory.
 ///
 /// This is an async version of [`std::fs::read_dir`](std::fs::read_dir)
@@ -29,9 +32,14 @@ use crate::blocking::JoinHandle;
 /// [`spawn_blocking`]: crate::task::spawn_blocking
 pub async fn read_dir(path: impl AsRef<Path>) -> io::Result<ReadDir> {
     let path = path.as_ref().to_owned();
-    let std = asyncify(|| std::fs::read_dir(path)).await?;
+    asyncify(|| -> io::Result<ReadDir> {
+        let mut std = std::fs::read_dir(path)?;
+        let mut buf = VecDeque::with_capacity(CHUNK_SIZE);
+        ReadDir::next_chunk(&mut buf, &mut std);
 
-    Ok(ReadDir(State::Idle(Some(std))))
+        Ok(ReadDir(State::Idle(Some((buf, std)))))
+    })
+    .await
 }
 
 /// Reads the entries in a directory.
@@ -58,8 +66,8 @@ pub struct ReadDir(State);
 
 #[derive(Debug)]
 enum State {
-    Idle(Option<std::fs::ReadDir>),
-    Pending(JoinHandle<(Option<io::Result<std::fs::DirEntry>>, std::fs::ReadDir)>),
+    Idle(Option<(VecDeque<io::Result<DirEntry>>, std::fs::ReadDir)>),
+    Pending(JoinHandle<(VecDeque<io::Result<DirEntry>>, std::fs::ReadDir)>),
 }
 
 impl ReadDir {
@@ -94,29 +102,57 @@ impl ReadDir {
     pub fn poll_next_entry(&mut self, cx: &mut Context<'_>) -> Poll<io::Result<Option<DirEntry>>> {
         loop {
             match self.0 {
-                State::Idle(ref mut std) => {
-                    let mut std = std.take().unwrap();
+                State::Idle(ref mut data) => {
+                    let (buf, _) = data.as_mut().unwrap();
+
+                    if let Some(ent) = buf.pop_front() {
+                        return Poll::Ready(ent.map(Some));
+                    };
+
+                    let (mut buf, mut std) = data.take().unwrap();
 
                     self.0 = State::Pending(spawn_blocking(move || {
-                        let ret = std.next();
-                        (ret, std)
+                        ReadDir::next_chunk(&mut buf, &mut std);
+                        (buf, std)
                     }));
                 }
                 State::Pending(ref mut rx) => {
-                    let (ret, std) = ready!(Pin::new(rx).poll(cx))?;
-                    self.0 = State::Idle(Some(std));
+                    let (mut buf, std) = ready!(Pin::new(rx).poll(cx))?;
 
-                    let ret = match ret {
-                        Some(Ok(std)) => Ok(Some(DirEntry(Arc::new(std)))),
+                    let ret = match buf.pop_front() {
+                        Some(Ok(x)) => Ok(Some(x)),
                         Some(Err(e)) => Err(e),
                         None => Ok(None),
                     };
 
+                    self.0 = State::Idle(Some((buf, std)));
+
                     return Poll::Ready(ret);
                 }
             }
         }
     }
+
+    fn next_chunk(buf: &mut VecDeque<io::Result<DirEntry>>, std: &mut std::fs::ReadDir) {
+        for ret in std.by_ref().take(CHUNK_SIZE) {
+            let success = ret.is_ok();
+
+            buf.push_back(ret.map(|std| DirEntry {
+                #[cfg(not(any(
+                    target_os = "solaris",
+                    target_os = "illumos",
+                    target_os = "haiku",
+                    target_os = "vxworks"
+                )))]
+                file_type: std.file_type().ok(),
+                std: Arc::new(std),
+            }));
+
+            if !success {
+                break;
+            }
+        }
+    }
 }
 
 feature! {
@@ -160,7 +196,16 @@ feature! {
 /// filesystem. Each entry can be inspected via methods to learn about the full
 /// path or possibly other metadata through per-platform extension traits.
 #[derive(Debug)]
-pub struct DirEntry(Arc<std::fs::DirEntry>);
+pub struct DirEntry {
+    #[cfg(not(any(
+        target_os = "solaris",
+        target_os = "illumos",
+        target_os = "haiku",
+        target_os = "vxworks"
+    )))]
+    file_type: Option<FileType>,
+    std: Arc<std::fs::DirEntry>,
+}
 
 impl DirEntry {
     /// Returns the full path to the file that this entry represents.
@@ -193,7 +238,7 @@ impl DirEntry {
     ///
     /// The exact text, of course, depends on what files you have in `.`.
     pub fn path(&self) -> PathBuf {
-        self.0.path()
+        self.std.path()
     }
 
     /// Returns the bare file name of this directory entry without any other
@@ -214,7 +259,7 @@ impl DirEntry {
     /// # }
     /// ```
     pub fn file_name(&self) -> OsString {
-        self.0.file_name()
+        self.std.file_name()
     }
 
     /// Returns the metadata for the file that this entry points at.
@@ -248,7 +293,7 @@ impl DirEntry {
     /// # }
     /// ```
     pub async fn metadata(&self) -> io::Result<Metadata> {
-        let std = self.0.clone();
+        let std = self.std.clone();
         asyncify(move || std.metadata()).await
     }
 
@@ -283,13 +328,23 @@ impl DirEntry {
     /// # }
     /// ```
     pub async fn file_type(&self) -> io::Result<FileType> {
-        let std = self.0.clone();
+        #[cfg(not(any(
+            target_os = "solaris",
+            target_os = "illumos",
+            target_os = "haiku",
+            target_os = "vxworks"
+        )))]
+        if let Some(file_type) = self.file_type {
+            return Ok(file_type);
+        }
+
+        let std = self.std.clone();
         asyncify(move || std.file_type()).await
     }
 
     /// Returns a reference to the underlying `std::fs::DirEntry`.
     #[cfg(unix)]
     pub(super) fn as_inner(&self) -> &std::fs::DirEntry {
-        &self.0
+        &self.std
     }
 }
diff --git a/tokio/src/fs/try_exists.rs b/tokio/src/fs/try_exists.rs
new file mode 100644
index 00000000000..069518bf946
--- /dev/null
+++ b/tokio/src/fs/try_exists.rs
@@ -0,0 +1,34 @@
+use crate::fs::asyncify;
+
+use std::io;
+use std::path::Path;
+
+/// Returns `Ok(true)` if the path points at an existing entity.
+///
+/// This function will traverse symbolic links to query information about the
+/// destination file. In case of broken symbolic links this will return `Ok(false)`.
+///
+/// This is the async equivalent of [`std::path::Path::try_exists`][std].
+///
+/// [std]: fn@std::path::Path::try_exists
+///
+/// # Examples
+///
+/// ```no_run
+/// use tokio::fs;
+///
+/// # async fn dox() -> std::io::Result<()> {
+/// fs::try_exists("foo.txt").await?;
+/// # Ok(())
+/// # }
+/// ```
+pub async fn try_exists(path: impl AsRef<Path>) -> io::Result<bool> {
+    let path = path.as_ref().to_owned();
+    // std's Path::try_exists is not available for current Rust min supported version.
+    // Current implementation is based on its internal implementation instead.
+    match asyncify(move || std::fs::metadata(path)).await {
+        Ok(_) => Ok(true),
+        Err(error) if error.kind() == std::io::ErrorKind::NotFound => Ok(false),
+        Err(error) => Err(error),
+    }
+}
diff --git a/tokio/src/fuzz.rs b/tokio/src/fuzz.rs
new file mode 100644
index 00000000000..d89718f0e0e
--- /dev/null
+++ b/tokio/src/fuzz.rs
@@ -0,0 +1 @@
+pub use crate::util::linked_list::tests::fuzz_linked_list;
diff --git a/tokio/src/io/async_fd.rs b/tokio/src/io/async_fd.rs
index 92fc6b38fd2..b71bcd56e70 100644
--- a/tokio/src/io/async_fd.rs
+++ b/tokio/src/io/async_fd.rs
@@ -65,8 +65,8 @@ use std::{task::Context, task::Poll};
 /// # Examples
 ///
 /// This example shows how to turn [`std::net::TcpStream`] asynchronous using
-/// `AsyncFd`.  It implements `read` as an async fn, and `AsyncWrite` as a trait
-/// to show how to implement both approaches.
+/// `AsyncFd`.  It implements the read/write operations both as an `async fn`
+/// and using the IO traits [`AsyncRead`] and [`AsyncWrite`].
 ///
 /// ```no_run
 /// use futures::ready;
@@ -74,7 +74,7 @@ use std::{task::Context, task::Poll};
 /// use std::net::TcpStream;
 /// use std::pin::Pin;
 /// use std::task::{Context, Poll};
-/// use tokio::io::AsyncWrite;
+/// use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
 /// use tokio::io::unix::AsyncFd;
 ///
 /// pub struct AsyncTcpStream {
@@ -99,6 +99,39 @@ use std::{task::Context, task::Poll};
 ///             }
 ///         }
 ///     }
+///
+///     pub async fn write(&self, buf: &[u8]) -> io::Result<usize> {
+///         loop {
+///             let mut guard = self.inner.writable().await?;
+///
+///             match guard.try_io(|inner| inner.get_ref().write(buf)) {
+///                 Ok(result) => return result,
+///                 Err(_would_block) => continue,
+///             }
+///         }
+///     }
+/// }
+///
+/// impl AsyncRead for AsyncTcpStream {
+///     fn poll_read(
+///         self: Pin<&mut Self>,
+///         cx: &mut Context<'_>,
+///         buf: &mut ReadBuf<'_>
+///     ) -> Poll<io::Result<()>> {
+///         loop {
+///             let mut guard = ready!(self.inner.poll_read_ready(cx))?;
+///
+///             let unfilled = buf.initialize_unfilled();
+///             match guard.try_io(|inner| inner.get_ref().read(unfilled)) {
+///                 Ok(Ok(len)) => {
+///                     buf.advance(len);
+///                     return Poll::Ready(Ok(()));
+///                 },
+///                 Ok(Err(err)) => return Poll::Ready(Err(err)),
+///                 Err(_would_block) => continue,
+///             }
+///         }
+///     }
 /// }
 ///
 /// impl AsyncWrite for AsyncTcpStream {
@@ -139,6 +172,8 @@ use std::{task::Context, task::Poll};
 /// [`writable`]: method@Self::writable
 /// [`AsyncFdReadyGuard`]: struct@self::AsyncFdReadyGuard
 /// [`TcpStream::poll_read_ready`]: struct@crate::net::TcpStream
+/// [`AsyncRead`]: trait@crate::io::AsyncRead
+/// [`AsyncWrite`]: trait@crate::io::AsyncWrite
 pub struct AsyncFd<T: AsRawFd> {
     registration: Registration,
     inner: Option<T>,
diff --git a/tokio/src/io/blocking.rs b/tokio/src/io/blocking.rs
index f6db4500af1..416573e9732 100644
--- a/tokio/src/io/blocking.rs
+++ b/tokio/src/io/blocking.rs
@@ -26,7 +26,7 @@ pub(crate) struct Buf {
     pos: usize,
 }
 
-pub(crate) const MAX_BUF: usize = 16 * 1024;
+pub(crate) const MAX_BUF: usize = 2 * 1024 * 1024;
 
 #[derive(Debug)]
 enum State<T> {
diff --git a/tokio/src/io/split.rs b/tokio/src/io/split.rs
index 2e0da95665f..f067b65a826 100644
--- a/tokio/src/io/split.rs
+++ b/tokio/src/io/split.rs
@@ -75,7 +75,10 @@ impl<T> ReadHalf<T> {
     /// This can be checked ahead of time by comparing the stream ID
     /// of the two halves.
     #[track_caller]
-    pub fn unsplit(self, wr: WriteHalf<T>) -> T {
+    pub fn unsplit(self, wr: WriteHalf<T>) -> T
+    where
+        T: Unpin,
+    {
         if self.is_pair_of(&wr) {
             drop(wr);
 
diff --git a/tokio/src/io/stdio_common.rs b/tokio/src/io/stdio_common.rs
index 2715ba7923a..06da761b858 100644
--- a/tokio/src/io/stdio_common.rs
+++ b/tokio/src/io/stdio_common.rs
@@ -108,14 +108,13 @@ where
 #[cfg(test)]
 #[cfg(not(loom))]
 mod tests {
+    use crate::io::blocking::MAX_BUF;
     use crate::io::AsyncWriteExt;
     use std::io;
     use std::pin::Pin;
     use std::task::Context;
     use std::task::Poll;
 
-    const MAX_BUF: usize = 16 * 1024;
-
     struct TextMockWriter;
 
     impl crate::io::AsyncWrite for TextMockWriter {
@@ -177,6 +176,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_splitter() {
         let data = str::repeat("█", MAX_BUF);
         let mut wr = super::SplitByUtf8BoundaryIfWindows::new(TextMockWriter);
@@ -190,6 +190,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_pseudo_text() {
         // In this test we write a piece of binary data, whose beginning is
         // text though. We then validate that even in this corner case buffer
diff --git a/tokio/src/io/util/copy_bidirectional.rs b/tokio/src/io/util/copy_bidirectional.rs
index c93060b361a..e1a7db127a7 100644
--- a/tokio/src/io/util/copy_bidirectional.rs
+++ b/tokio/src/io/util/copy_bidirectional.rs
@@ -1,8 +1,8 @@
 use super::copy::CopyBuffer;
 
+use crate::future::poll_fn;
 use crate::io::{AsyncRead, AsyncWrite};
 
-use std::future::Future;
 use std::io;
 use std::pin::Pin;
 use std::task::{Context, Poll};
@@ -13,13 +13,6 @@ enum TransferState {
     Done(u64),
 }
 
-struct CopyBidirectional<'a, A: ?Sized, B: ?Sized> {
-    a: &'a mut A,
-    b: &'a mut B,
-    a_to_b: TransferState,
-    b_to_a: TransferState,
-}
-
 fn transfer_one_direction<A, B>(
     cx: &mut Context<'_>,
     state: &mut TransferState,
@@ -48,35 +41,6 @@ where
         }
     }
 }
-
-impl<'a, A, B> Future for CopyBidirectional<'a, A, B>
-where
-    A: AsyncRead + AsyncWrite + Unpin + ?Sized,
-    B: AsyncRead + AsyncWrite + Unpin + ?Sized,
-{
-    type Output = io::Result<(u64, u64)>;
-
-    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        // Unpack self into mut refs to each field to avoid borrow check issues.
-        let CopyBidirectional {
-            a,
-            b,
-            a_to_b,
-            b_to_a,
-        } = &mut *self;
-
-        let a_to_b = transfer_one_direction(cx, a_to_b, &mut *a, &mut *b)?;
-        let b_to_a = transfer_one_direction(cx, b_to_a, &mut *b, &mut *a)?;
-
-        // It is not a problem if ready! returns early because transfer_one_direction for the
-        // other direction will keep returning TransferState::Done(count) in future calls to poll
-        let a_to_b = ready!(a_to_b);
-        let b_to_a = ready!(b_to_a);
-
-        Poll::Ready(Ok((a_to_b, b_to_a)))
-    }
-}
-
 /// Copies data in both directions between `a` and `b`.
 ///
 /// This function returns a future that will read from both streams,
@@ -110,11 +74,18 @@ where
     A: AsyncRead + AsyncWrite + Unpin + ?Sized,
     B: AsyncRead + AsyncWrite + Unpin + ?Sized,
 {
-    CopyBidirectional {
-        a,
-        b,
-        a_to_b: TransferState::Running(CopyBuffer::new()),
-        b_to_a: TransferState::Running(CopyBuffer::new()),
-    }
+    let mut a_to_b = TransferState::Running(CopyBuffer::new());
+    let mut b_to_a = TransferState::Running(CopyBuffer::new());
+    poll_fn(|cx| {
+        let a_to_b = transfer_one_direction(cx, &mut a_to_b, a, b)?;
+        let b_to_a = transfer_one_direction(cx, &mut b_to_a, b, a)?;
+
+        // It is not a problem if ready! returns early because transfer_one_direction for the
+        // other direction will keep returning TransferState::Done(count) in future calls to poll
+        let a_to_b = ready!(a_to_b);
+        let b_to_a = ready!(b_to_a);
+
+        Poll::Ready(Ok((a_to_b, b_to_a)))
+    })
     .await
 }
diff --git a/tokio/src/io/util/read.rs b/tokio/src/io/util/read.rs
index edc9d5a9e6e..a1f9c8a0505 100644
--- a/tokio/src/io/util/read.rs
+++ b/tokio/src/io/util/read.rs
@@ -48,7 +48,7 @@ where
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<usize>> {
         let me = self.project();
-        let mut buf = ReadBuf::new(*me.buf);
+        let mut buf = ReadBuf::new(me.buf);
         ready!(Pin::new(me.reader).poll_read(cx, &mut buf))?;
         Poll::Ready(Ok(buf.filled().len()))
     }
diff --git a/tokio/src/lib.rs b/tokio/src/lib.rs
index e745fe9995f..688dd0c4d42 100644
--- a/tokio/src/lib.rs
+++ b/tokio/src/lib.rs
@@ -174,12 +174,15 @@
 //! swapping the currently running task on each thread. However, this kind of
 //! swapping can only happen at `.await` points, so code that spends a long time
 //! without reaching an `.await` will prevent other tasks from running. To
-//! combat this, Tokio provides two kinds of threads: Core threads and blocking
-//! threads. The core threads are where all asynchronous code runs, and Tokio
-//! will by default spawn one for each CPU core. The blocking threads are
-//! spawned on demand, can be used to run blocking code that would otherwise
-//! block other tasks from running and are kept alive when not used for a certain
-//! amount of time which can be configured with [`thread_keep_alive`].
+//! combat this, Tokio provides two kinds of threads: Core threads and blocking threads.
+//!
+//! The core threads are where all asynchronous code runs, and Tokio will by default
+//! spawn one for each CPU core. You can use the environment variable `TOKIO_WORKER_THREADS`
+//! to override the default value.
+//!
+//! The blocking threads are spawned on demand, can be used to run blocking code
+//! that would otherwise block other tasks from running and are kept alive when
+//! not used for a certain amount of time which can be configured with [`thread_keep_alive`].
 //! Since it is not possible for Tokio to swap out blocking tasks, like it
 //! can do with asynchronous code, the upper limit on the number of blocking
 //! threads is very large. These limits can be configured on the [`Builder`].
@@ -381,7 +384,33 @@
 //! [unstable features]: https://internals.rust-lang.org/t/feature-request-unstable-opt-in-non-transitive-crate-features/16193#why-not-a-crate-feature-2
 //! [feature flags]: https://doc.rust-lang.org/cargo/reference/manifest.html#the-features-section
 //!
-//! ## WASM support
+//! ## Supported platforms
+//!
+//! Tokio currently guarantees support for the following platforms:
+//!
+//!  * Linux
+//!  * Windows
+//!  * Android (API level 21)
+//!  * macOS
+//!  * iOS
+//!  * FreeBSD
+//!
+//! Tokio will continue to support these platforms in the future. However,
+//! future releases may change requirements such as the minimum required libc
+//! version on Linux, the API level on Android, or the supported FreeBSD
+//! release.
+//!
+//! Beyond the above platforms, Tokio is intended to work on all platforms
+//! supported by the mio crate. You can find a longer list [in mio's
+//! documentation][mio-supported]. However, these additional platforms may
+//! become unsupported in the future.
+//!
+//! Note that Wine is considered to be a different platform from Windows. See
+//! mio's documentation for more information on Wine support.
+//!
+//! [mio-supported]: https://crates.io/crates/mio#platforms
+//!
+//! ### WASM support
 //!
 //! Tokio has some limited support for the WASM platform. Without the
 //! `tokio_unstable` flag, the following features are supported:
@@ -628,3 +657,6 @@ cfg_macros! {
 #[cfg(feature = "io-util")]
 #[cfg(test)]
 fn is_unpin<T: Unpin>() {}
+
+#[cfg(fuzzing)]
+pub mod fuzz;
diff --git a/tokio/src/loom/mocked.rs b/tokio/src/loom/mocked.rs
index 1c4a32dd863..56dc1a06344 100644
--- a/tokio/src/loom/mocked.rs
+++ b/tokio/src/loom/mocked.rs
@@ -25,6 +25,13 @@ pub(crate) mod sync {
         }
     }
     pub(crate) use loom::sync::*;
+
+    pub(crate) mod atomic {
+        pub(crate) use loom::sync::atomic::*;
+
+        // TODO: implement a loom version
+        pub(crate) type StaticAtomicU64 = std::sync::atomic::AtomicU64;
+    }
 }
 
 pub(crate) mod rand {
diff --git a/tokio/src/loom/std/atomic_u64.rs b/tokio/src/loom/std/atomic_u64.rs
index 5d1d8a89f8b..ce391be3e11 100644
--- a/tokio/src/loom/std/atomic_u64.rs
+++ b/tokio/src/loom/std/atomic_u64.rs
@@ -7,12 +7,13 @@
 // `#[cfg(target_has_atomic = "64")]`.
 // Refs: https://github.com/rust-lang/rust/tree/master/src/librustc_target
 cfg_has_atomic_u64! {
-    pub(crate) use std::sync::atomic::AtomicU64;
+    #[path = "atomic_u64_native.rs"]
+    mod imp;
 }
 
 cfg_not_has_atomic_u64! {
     #[path = "atomic_u64_as_mutex.rs"]
-    mod atomic_u64_as_mutex;
-
-    pub(crate) use atomic_u64_as_mutex::AtomicU64;
+    mod imp;
 }
+
+pub(crate) use imp::{AtomicU64, StaticAtomicU64};
diff --git a/tokio/src/loom/std/atomic_u64_as_mutex.rs b/tokio/src/loom/std/atomic_u64_as_mutex.rs
index 84ddff06fb8..9b3b6fac68c 100644
--- a/tokio/src/loom/std/atomic_u64_as_mutex.rs
+++ b/tokio/src/loom/std/atomic_u64_as_mutex.rs
@@ -1,18 +1,24 @@
 use crate::loom::sync::Mutex;
 use std::sync::atomic::Ordering;
 
+cfg_has_const_mutex_new! {
+    #[path = "atomic_u64_static_const_new.rs"]
+    mod static_macro;
+}
+
+cfg_not_has_const_mutex_new! {
+    #[path = "atomic_u64_static_once_cell.rs"]
+    mod static_macro;
+}
+
+pub(crate) use static_macro::StaticAtomicU64;
+
 #[derive(Debug)]
 pub(crate) struct AtomicU64 {
     inner: Mutex<u64>,
 }
 
 impl AtomicU64 {
-    pub(crate) fn new(val: u64) -> Self {
-        Self {
-            inner: Mutex::new(val),
-        }
-    }
-
     pub(crate) fn load(&self, _: Ordering) -> u64 {
         *self.inner.lock()
     }
diff --git a/tokio/src/loom/std/atomic_u64_native.rs b/tokio/src/loom/std/atomic_u64_native.rs
new file mode 100644
index 00000000000..08adb28629a
--- /dev/null
+++ b/tokio/src/loom/std/atomic_u64_native.rs
@@ -0,0 +1,4 @@
+pub(crate) use std::sync::atomic::{AtomicU64, Ordering};
+
+/// Alias `AtomicU64` to `StaticAtomicU64`
+pub(crate) type StaticAtomicU64 = AtomicU64;
diff --git a/tokio/src/loom/std/atomic_u64_static_const_new.rs b/tokio/src/loom/std/atomic_u64_static_const_new.rs
new file mode 100644
index 00000000000..a4215342b68
--- /dev/null
+++ b/tokio/src/loom/std/atomic_u64_static_const_new.rs
@@ -0,0 +1,12 @@
+use super::AtomicU64;
+use crate::loom::sync::Mutex;
+
+pub(crate) type StaticAtomicU64 = AtomicU64;
+
+impl AtomicU64 {
+    pub(crate) const fn new(val: u64) -> Self {
+        Self {
+            inner: Mutex::const_new(val),
+        }
+    }
+}
diff --git a/tokio/src/loom/std/atomic_u64_static_once_cell.rs b/tokio/src/loom/std/atomic_u64_static_once_cell.rs
new file mode 100644
index 00000000000..40c6172a524
--- /dev/null
+++ b/tokio/src/loom/std/atomic_u64_static_once_cell.rs
@@ -0,0 +1,57 @@
+use super::AtomicU64;
+use crate::loom::sync::{atomic::Ordering, Mutex};
+use crate::util::once_cell::OnceCell;
+
+pub(crate) struct StaticAtomicU64 {
+    init: u64,
+    cell: OnceCell<Mutex<u64>>,
+}
+
+impl AtomicU64 {
+    pub(crate) fn new(val: u64) -> Self {
+        Self {
+            inner: Mutex::new(val),
+        }
+    }
+}
+
+impl StaticAtomicU64 {
+    pub(crate) const fn new(val: u64) -> StaticAtomicU64 {
+        StaticAtomicU64 {
+            init: val,
+            cell: OnceCell::new(),
+        }
+    }
+
+    pub(crate) fn load(&self, order: Ordering) -> u64 {
+        *self.inner().lock()
+    }
+
+    pub(crate) fn fetch_add(&self, val: u64, order: Ordering) -> u64 {
+        let mut lock = self.inner().lock();
+        let prev = *lock;
+        *lock = prev + val;
+        prev
+    }
+
+    pub(crate) fn compare_exchange_weak(
+        &self,
+        current: u64,
+        new: u64,
+        _success: Ordering,
+        _failure: Ordering,
+    ) -> Result<u64, u64> {
+        let mut lock = self.inner().lock();
+
+        if *lock == current {
+            *lock = new;
+            Ok(current)
+        } else {
+            Err(*lock)
+        }
+    }
+
+    fn inner(&self) -> &Mutex<u64> {
+        self.cell.get(|| Mutex::new(self.init))
+    }
+}
diff --git a/tokio/src/loom/std/mod.rs b/tokio/src/loom/std/mod.rs
index 1fc0032a87d..6bd1ad93dcf 100644
--- a/tokio/src/loom/std/mod.rs
+++ b/tokio/src/loom/std/mod.rs
@@ -71,7 +71,7 @@ pub(crate) mod sync {
     pub(crate) mod atomic {
         pub(crate) use crate::loom::std::atomic_u16::AtomicU16;
         pub(crate) use crate::loom::std::atomic_u32::AtomicU32;
-        pub(crate) use crate::loom::std::atomic_u64::AtomicU64;
+        pub(crate) use crate::loom::std::atomic_u64::{AtomicU64, StaticAtomicU64};
         pub(crate) use crate::loom::std::atomic_usize::AtomicUsize;
 
         pub(crate) use std::sync::atomic::{fence, AtomicBool, AtomicPtr, AtomicU8, Ordering};
@@ -81,7 +81,27 @@ pub(crate) mod sync {
 pub(crate) mod sys {
     #[cfg(feature = "rt-multi-thread")]
     pub(crate) fn num_cpus() -> usize {
-        usize::max(1, num_cpus::get())
+        const ENV_WORKER_THREADS: &str = "TOKIO_WORKER_THREADS";
+
+        match std::env::var(ENV_WORKER_THREADS) {
+            Ok(s) => {
+                let n = s.parse().unwrap_or_else(|e| {
+                    panic!(
+                        "\"{}\" must be usize, error: {}, value: {}",
+                        ENV_WORKER_THREADS, e, s
+                    )
+                });
+                assert!(n > 0, "\"{}\" cannot be set to 0", ENV_WORKER_THREADS);
+                n
+            }
+            Err(std::env::VarError::NotPresent) => usize::max(1, num_cpus::get()),
+            Err(std::env::VarError::NotUnicode(e)) => {
+                panic!(
+                    "\"{}\" must be valid unicode, error: {:?}",
+                    ENV_WORKER_THREADS, e
+                )
+            }
+        }
     }
 
     #[cfg(not(feature = "rt-multi-thread"))]
diff --git a/tokio/src/macros/cfg.rs b/tokio/src/macros/cfg.rs
index 2eea344b516..1c66d24147a 100644
--- a/tokio/src/macros/cfg.rs
+++ b/tokio/src/macros/cfg.rs
@@ -461,14 +461,14 @@ macro_rules! cfg_not_coop {
 macro_rules! cfg_has_atomic_u64 {
     ($($item:item)*) => {
         $(
-            #[cfg(not(any(
-                target_arch = "arm",
-                target_arch = "mips",
-                target_arch = "powerpc",
-                target_arch = "riscv32",
-                tokio_wasm,
-                tokio_no_atomic_u64,
-            )))]
+            #[cfg_attr(
+                not(tokio_no_target_has_atomic),
+                cfg(all(target_has_atomic = "64", not(tokio_no_atomic_u64))
+            ))]
+            #[cfg_attr(
+                tokio_no_target_has_atomic,
+                cfg(not(tokio_no_atomic_u64))
+            )]
             $item
         )*
     }
@@ -477,14 +477,14 @@ macro_rules! cfg_has_atomic_u64 {
 macro_rules! cfg_not_has_atomic_u64 {
     ($($item:item)*) => {
         $(
-            #[cfg(any(
-                target_arch = "arm",
-                target_arch = "mips",
-                target_arch = "powerpc",
-                target_arch = "riscv32",
-                tokio_wasm,
-                tokio_no_atomic_u64,
+            #[cfg_attr(
+                not(tokio_no_target_has_atomic),
+                cfg(any(not(target_has_atomic = "64"), tokio_no_atomic_u64)
             ))]
+            #[cfg_attr(
+                tokio_no_target_has_atomic,
+                cfg(tokio_no_atomic_u64)
+            )]
             $item
         )*
     }
diff --git a/tokio/src/macros/join.rs b/tokio/src/macros/join.rs
index 7e85203c0c4..8a0198600b2 100644
--- a/tokio/src/macros/join.rs
+++ b/tokio/src/macros/join.rs
@@ -158,7 +158,9 @@ macro_rules! join {
 
     // ===== Entry point =====
 
-    ( $($e:expr),* $(,)?) => {
+    ( $($e:expr),+ $(,)?) => {
         $crate::join!(@{ () (0) } $($e,)*)
     };
+
+    () => { async {}.await }
 }
diff --git a/tokio/src/macros/try_join.rs b/tokio/src/macros/try_join.rs
index 597cd5df021..7b123709231 100644
--- a/tokio/src/macros/try_join.rs
+++ b/tokio/src/macros/try_join.rs
@@ -210,7 +210,9 @@ macro_rules! try_join {
 
     // ===== Entry point =====
 
-    ( $($e:expr),* $(,)?) => {
+    ( $($e:expr),+ $(,)?) => {
         $crate::try_join!(@{ () (0) } $($e,)*)
     };
+
+    () => { async { Ok(()) }.await }
 }
diff --git a/tokio/src/net/tcp/listener.rs b/tokio/src/net/tcp/listener.rs
index 4a022fa2a2c..4441313703e 100644
--- a/tokio/src/net/tcp/listener.rs
+++ b/tokio/src/net/tcp/listener.rs
@@ -195,15 +195,22 @@ impl TcpListener {
     /// Creates new `TcpListener` from a `std::net::TcpListener`.
     ///
     /// This function is intended to be used to wrap a TCP listener from the
-    /// standard library in the Tokio equivalent. The conversion assumes nothing
-    /// about the underlying listener; it is left up to the user to set it in
-    /// non-blocking mode.
+    /// standard library in the Tokio equivalent.
     ///
     /// This API is typically paired with the `socket2` crate and the `Socket`
     /// type to build up and customize a listener before it's shipped off to the
     /// backing event loop. This allows configuration of options like
     /// `SO_REUSEPORT`, binding to multiple addresses, etc.
     ///
+    /// # Notes
+    ///
+    /// The caller is responsible for ensuring that the listener is in
+    /// non-blocking mode. Otherwise all I/O operations on the listener
+    /// will block the thread, which will cause unexpected behavior.
+    /// Non-blocking mode can be set using [`set_nonblocking`].
+    ///
+    /// [`set_nonblocking`]: std::net::TcpListener::set_nonblocking
+    ///
     /// # Examples
     ///
     /// ```rust,no_run
diff --git a/tokio/src/net/tcp/socket.rs b/tokio/src/net/tcp/socket.rs
index 94534110460..09349fe53eb 100644
--- a/tokio/src/net/tcp/socket.rs
+++ b/tokio/src/net/tcp/socket.rs
@@ -670,6 +670,15 @@ impl TcpSocket {
     /// [`std::net::TcpStream`]: struct@std::net::TcpStream
     /// [`socket2`]: https://docs.rs/socket2/
     ///
+    /// # Notes
+    ///
+    /// The caller is responsible for ensuring that the socket is in
+    /// non-blocking mode. Otherwise all I/O operations on the socket
+    /// will block the thread, which will cause unexpected behavior.
+    /// Non-blocking mode can be set using [`set_nonblocking`].
+    ///
+    /// [`set_nonblocking`]: std::net::TcpStream::set_nonblocking
+    ///
     /// # Examples
     ///
     /// ```
@@ -678,8 +687,8 @@ impl TcpSocket {
     ///
     /// #[tokio::main]
     /// async fn main() -> std::io::Result<()> {
-    ///
     ///     let socket2_socket = Socket::new(Domain::IPV4, Type::STREAM, None)?;
+    ///     socket2_socket.set_nonblocking(true)?;
     ///
     ///     let socket = TcpSocket::from_std_stream(socket2_socket.into());
     ///
diff --git a/tokio/src/net/tcp/split.rs b/tokio/src/net/tcp/split.rs
index 2ea08b3dc32..343d4fde7d5 100644
--- a/tokio/src/net/tcp/split.rs
+++ b/tokio/src/net/tcp/split.rs
@@ -145,6 +145,12 @@ impl ReadHalf<'_> {
     /// can be used to concurrently read / write to the same socket on a single
     /// task without splitting the socket.
     ///
+    /// The function may complete without the socket being ready. This is a
+    /// false-positive and attempting an operation will return with
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
+    ///
     /// This function is equivalent to [`TcpStream::ready`].
     ///
     /// # Cancel safety
@@ -273,6 +279,12 @@ impl WriteHalf<'_> {
     /// can be used to concurrently read / write to the same socket on a single
     /// task without splitting the socket.
     ///
+    /// The function may complete without the socket being ready. This is a
+    /// false-positive and attempting an operation will return with
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
+    ///
     /// This function is equivalent to [`TcpStream::ready`].
     ///
     /// # Cancel safety
diff --git a/tokio/src/net/tcp/split_owned.rs b/tokio/src/net/tcp/split_owned.rs
index e2cfdefe1a3..53fc5f06fd7 100644
--- a/tokio/src/net/tcp/split_owned.rs
+++ b/tokio/src/net/tcp/split_owned.rs
@@ -200,6 +200,12 @@ impl OwnedReadHalf {
     /// can be used to concurrently read / write to the same socket on a single
     /// task without splitting the socket.
     ///
+    /// The function may complete without the socket being ready. This is a
+    /// false-positive and attempting an operation will return with
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
+    ///
     /// This function is equivalent to [`TcpStream::ready`].
     ///
     /// # Cancel safety
@@ -355,6 +361,12 @@ impl OwnedWriteHalf {
     /// can be used to concurrently read / write to the same socket on a single
     /// task without splitting the socket.
     ///
+    /// The function may complete without the socket being ready. This is a
+    /// false-positive and attempting an operation will return with
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
+    ///
     /// This function is equivalent to [`TcpStream::ready`].
     ///
     /// # Cancel safety
@@ -478,12 +490,12 @@ impl AsyncWrite for OwnedWriteHalf {
 
 impl AsRef<TcpStream> for OwnedReadHalf {
     fn as_ref(&self) -> &TcpStream {
-        &*self.inner
+        &self.inner
     }
 }
 
 impl AsRef<TcpStream> for OwnedWriteHalf {
     fn as_ref(&self) -> &TcpStream {
-        &*self.inner
+        &self.inner
     }
 }
diff --git a/tokio/src/net/tcp/stream.rs b/tokio/src/net/tcp/stream.rs
index 09045d9c665..a99e6badad1 100644
--- a/tokio/src/net/tcp/stream.rs
+++ b/tokio/src/net/tcp/stream.rs
@@ -165,9 +165,16 @@ impl TcpStream {
     /// Creates new `TcpStream` from a `std::net::TcpStream`.
     ///
     /// This function is intended to be used to wrap a TCP stream from the
-    /// standard library in the Tokio equivalent. The conversion assumes nothing
-    /// about the underlying stream; it is left up to the user to set it in
-    /// non-blocking mode.
+    /// standard library in the Tokio equivalent.
+    ///
+    /// # Notes
+    ///
+    /// The caller is responsible for ensuring that the stream is in
+    /// non-blocking mode. Otherwise all I/O operations on the stream
+    /// will block the thread, which will cause unexpected behavior.
+    /// Non-blocking mode can be set using [`set_nonblocking`].
+    ///
+    /// [`set_nonblocking`]: std::net::TcpStream::set_nonblocking
     ///
     /// # Examples
     ///
@@ -377,6 +384,12 @@ impl TcpStream {
     /// can be used to concurrently read / write to the same socket on a single
     /// task without splitting the socket.
     ///
+    /// The function may complete without the socket being ready. This is a
+    /// false-positive and attempting an operation will return with
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
+    ///
     /// # Cancel safety
     ///
     /// This method is cancel safe. Once a readiness event occurs, the method
diff --git a/tokio/src/net/udp.rs b/tokio/src/net/udp.rs
index 8c255f187e1..ff6878ededa 100644
--- a/tokio/src/net/udp.rs
+++ b/tokio/src/net/udp.rs
@@ -179,14 +179,21 @@ impl UdpSocket {
     /// Creates new `UdpSocket` from a previously bound `std::net::UdpSocket`.
     ///
     /// This function is intended to be used to wrap a UDP socket from the
-    /// standard library in the Tokio equivalent. The conversion assumes nothing
-    /// about the underlying socket; it is left up to the user to set it in
-    /// non-blocking mode.
+    /// standard library in the Tokio equivalent.
     ///
     /// This can be used in conjunction with socket2's `Socket` interface to
     /// configure a socket before it's handed off, such as setting options like
     /// `reuse_address` or binding to multiple addresses.
     ///
+    /// # Notes
+    ///
+    /// The caller is responsible for ensuring that the socket is in
+    /// non-blocking mode. Otherwise all I/O operations on the socket
+    /// will block the thread, which will cause unexpected behavior.
+    /// Non-blocking mode can be set using [`set_nonblocking`].
+    ///
+    /// [`set_nonblocking`]: std::net::UdpSocket::set_nonblocking
+    ///
     /// # Panics
     ///
     /// This function panics if thread-local runtime is not set.
@@ -357,7 +364,9 @@ impl UdpSocket {
     ///
     /// The function may complete without the socket being ready. This is a
     /// false-positive and attempting an operation will return with
-    /// `io::ErrorKind::WouldBlock`.
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
     ///
     /// # Cancel safety
     ///
diff --git a/tokio/src/net/unix/datagram/socket.rs b/tokio/src/net/unix/datagram/socket.rs
index 8e455f67187..7b56f45a0b9 100644
--- a/tokio/src/net/unix/datagram/socket.rs
+++ b/tokio/src/net/unix/datagram/socket.rs
@@ -104,7 +104,9 @@ impl UnixDatagram {
     ///
     /// The function may complete without the socket being ready. This is a
     /// false-positive and attempting an operation will return with
-    /// `io::ErrorKind::WouldBlock`.
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
     ///
     /// # Cancel safety
     ///
@@ -424,9 +426,16 @@ impl UnixDatagram {
     /// Creates new `UnixDatagram` from a `std::os::unix::net::UnixDatagram`.
     ///
     /// This function is intended to be used to wrap a UnixDatagram from the
-    /// standard library in the Tokio equivalent. The conversion assumes
-    /// nothing about the underlying datagram; it is left up to the user to set
-    /// it in non-blocking mode.
+    /// standard library in the Tokio equivalent.
+    ///
+    /// # Notes
+    ///
+    /// The caller is responsible for ensuring that the socker is in
+    /// non-blocking mode. Otherwise all I/O operations on the socket
+    /// will block the thread, which will cause unexpected behavior.
+    /// Non-blocking mode can be set using [`set_nonblocking`].
+    ///
+    /// [`set_nonblocking`]: std::os::unix::net::UnixDatagram::set_nonblocking
     ///
     /// # Panics
     ///
@@ -468,21 +477,19 @@ impl UnixDatagram {
     /// Turns a [`tokio::net::UnixDatagram`] into a [`std::os::unix::net::UnixDatagram`].
     ///
     /// The returned [`std::os::unix::net::UnixDatagram`] will have nonblocking
-    /// mode set as `true`.  Use [`set_nonblocking`] to change the blocking mode
+    /// mode set as `true`. Use [`set_nonblocking`] to change the blocking mode
     /// if needed.
     ///
     /// # Examples
     ///
     /// ```rust,no_run
-    /// use std::error::Error;
-    ///
-    /// #[tokio::main]
-    /// async fn main() -> Result<(), Box<dyn Error>> {
-    ///     let tokio_socket = tokio::net::UnixDatagram::bind("127.0.0.1:0")?;
-    ///     let std_socket = tokio_socket.into_std()?;
-    ///     std_socket.set_nonblocking(false)?;
-    ///     Ok(())
-    /// }
+    /// # use std::error::Error;
+    /// # async fn dox() -> Result<(), Box<dyn Error>> {
+    /// let tokio_socket = tokio::net::UnixDatagram::bind("/path/to/the/socket")?;
+    /// let std_socket = tokio_socket.into_std()?;
+    /// std_socket.set_nonblocking(false)?;
+    /// # Ok(())
+    /// # }
     /// ```
     ///
     /// [`tokio::net::UnixDatagram`]: UnixDatagram
diff --git a/tokio/src/net/unix/listener.rs b/tokio/src/net/unix/listener.rs
index fbea3e76a1a..9887f7343be 100644
--- a/tokio/src/net/unix/listener.rs
+++ b/tokio/src/net/unix/listener.rs
@@ -73,9 +73,31 @@ impl UnixListener {
     /// Creates new `UnixListener` from a `std::os::unix::net::UnixListener `.
     ///
     /// This function is intended to be used to wrap a UnixListener from the
-    /// standard library in the Tokio equivalent. The conversion assumes
-    /// nothing about the underlying listener; it is left up to the user to set
-    /// it in non-blocking mode.
+    /// standard library in the Tokio equivalent.
+    ///
+    /// # Notes
+    ///
+    /// The caller is responsible for ensuring that the listener is in
+    /// non-blocking mode. Otherwise all I/O operations on the listener
+    /// will block the thread, which will cause unexpected behavior.
+    /// Non-blocking mode can be set using [`set_nonblocking`].
+    ///
+    /// [`set_nonblocking`]: std::os::unix::net::UnixListener::set_nonblocking
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use tokio::net::UnixListener;
+    /// use std::os::unix::net::UnixListener as StdUnixListener;
+    /// # use std::error::Error;
+    ///
+    /// # async fn dox() -> Result<(), Box<dyn Error>> {
+    /// let std_listener = StdUnixListener::bind("/path/to/the/socket")?;
+    /// std_listener.set_nonblocking(true)?;
+    /// let listener = UnixListener::from_std(std_listener)?;
+    /// # Ok(())
+    /// # }
+    /// ```
     ///
     /// # Panics
     ///
@@ -95,20 +117,18 @@ impl UnixListener {
     /// Turns a [`tokio::net::UnixListener`] into a [`std::os::unix::net::UnixListener`].
     ///
     /// The returned [`std::os::unix::net::UnixListener`] will have nonblocking mode
-    /// set as `true`.  Use [`set_nonblocking`] to change the blocking mode if needed.
+    /// set as `true`. Use [`set_nonblocking`] to change the blocking mode if needed.
     ///
     /// # Examples
     ///
     /// ```rust,no_run
-    /// use std::error::Error;
-    ///
-    /// #[tokio::main]
-    /// async fn main() -> Result<(), Box<dyn Error>> {
-    ///     let tokio_listener = tokio::net::UnixListener::bind("127.0.0.1:0")?;
-    ///     let std_listener = tokio_listener.into_std()?;
-    ///     std_listener.set_nonblocking(false)?;
-    ///     Ok(())
-    /// }
+    /// # use std::error::Error;
+    /// # async fn dox() -> Result<(), Box<dyn Error>> {
+    /// let tokio_listener = tokio::net::UnixListener::bind("/path/to/the/socket")?;
+    /// let std_listener = tokio_listener.into_std()?;
+    /// std_listener.set_nonblocking(false)?;
+    /// # Ok(())
+    /// # }
     /// ```
     ///
     /// [`tokio::net::UnixListener`]: UnixListener
diff --git a/tokio/src/net/unix/mod.rs b/tokio/src/net/unix/mod.rs
index 97b632744dc..a49b70af34a 100644
--- a/tokio/src/net/unix/mod.rs
+++ b/tokio/src/net/unix/mod.rs
@@ -1,4 +1,4 @@
-//! Unix domain socket utility types.
+//! Unix specific network types.
 // This module does not currently provide any public API, but it was
 // unintentionally defined as a public module. Hide it from the documentation
 // instead of changing it to a private module to avoid breakage.
@@ -22,6 +22,8 @@ pub(crate) use stream::UnixStream;
 mod ucred;
 pub use ucred::UCred;
 
+pub mod pipe;
+
 /// A type representing process and process group IDs.
 #[allow(non_camel_case_types)]
 pub type uid_t = u32;
diff --git a/tokio/src/net/unix/pipe.rs b/tokio/src/net/unix/pipe.rs
new file mode 100644
index 00000000000..0775717b0c6
--- /dev/null
+++ b/tokio/src/net/unix/pipe.rs
@@ -0,0 +1,1206 @@
+//! Unix pipe types.
+
+use crate::io::interest::Interest;
+use crate::io::{AsyncRead, AsyncWrite, PollEvented, ReadBuf, Ready};
+
+use mio::unix::pipe as mio_pipe;
+use std::fs::File;
+use std::io::{self, Read, Write};
+use std::os::unix::fs::{FileTypeExt, OpenOptionsExt};
+use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
+use std::path::Path;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+cfg_io_util! {
+    use bytes::BufMut;
+}
+
+/// Options and flags which can be used to configure how a FIFO file is opened.
+///
+/// This builder allows configuring how to create a pipe end from a FIFO file.
+/// Generally speaking, when using `OpenOptions`, you'll first call [`new`],
+/// then chain calls to methods to set each option, then call either
+/// [`open_receiver`] or [`open_sender`], passing the path of the FIFO file you
+/// are trying to open. This will give you a [`io::Result`][result] with a pipe
+/// end inside that you can further operate on.
+///
+/// [`new`]: OpenOptions::new
+/// [`open_receiver`]: OpenOptions::open_receiver
+/// [`open_sender`]: OpenOptions::open_sender
+/// [result]: std::io::Result
+///
+/// # Examples
+///
+/// Opening a pair of pipe ends from a FIFO file:
+///
+/// ```no_run
+/// use tokio::net::unix::pipe;
+/// # use std::error::Error;
+///
+/// const FIFO_NAME: &str = "path/to/a/fifo";
+///
+/// # async fn dox() -> Result<(), Box<dyn Error>> {
+/// let rx = pipe::OpenOptions::new().open_receiver(FIFO_NAME)?;
+/// let tx = pipe::OpenOptions::new().open_sender(FIFO_NAME)?;
+/// # Ok(())
+/// # }
+/// ```
+///
+/// Opening a [`Sender`] on Linux when you are sure the file is a FIFO:
+///
+/// ```ignore
+/// use tokio::net::unix::pipe;
+/// use nix::{unistd::mkfifo, sys::stat::Mode};
+/// # use std::error::Error;
+///
+/// // Our program has exclusive access to this path.
+/// const FIFO_NAME: &str = "path/to/a/new/fifo";
+///
+/// # async fn dox() -> Result<(), Box<dyn Error>> {
+/// mkfifo(FIFO_NAME, Mode::S_IRWXU)?;
+/// let tx = pipe::OpenOptions::new()
+///     .read_write(true)
+///     .unchecked(true)
+///     .open_sender(FIFO_NAME)?;
+/// # Ok(())
+/// # }
+/// ```
+#[derive(Clone, Debug)]
+pub struct OpenOptions {
+    #[cfg(target_os = "linux")]
+    read_write: bool,
+    unchecked: bool,
+}
+
+impl OpenOptions {
+    /// Creates a blank new set of options ready for configuration.
+    ///
+    /// All options are initially set to `false`.
+    pub fn new() -> OpenOptions {
+        OpenOptions {
+            #[cfg(target_os = "linux")]
+            read_write: false,
+            unchecked: false,
+        }
+    }
+
+    /// Sets the option for read-write access.
+    ///
+    /// This option, when true, will indicate that a FIFO file will be opened
+    /// in read-write access mode. This operation is not defined by the POSIX
+    /// standard and is only guaranteed to work on Linux.
+    ///
+    /// # Examples
+    ///
+    /// Opening a [`Sender`] even if there are no open reading ends:
+    ///
+    /// ```ignore
+    /// use tokio::net::unix::pipe;
+    ///
+    /// let tx = pipe::OpenOptions::new()
+    ///     .read_write(true)
+    ///     .open_sender("path/to/a/fifo");
+    /// ```
+    ///
+    /// Opening a resilient [`Receiver`] i.e. a reading pipe end which will not
+    /// fail with [`UnexpectedEof`] during reading if all writing ends of the
+    /// pipe close the FIFO file.
+    ///
+    /// [`UnexpectedEof`]: std::io::ErrorKind::UnexpectedEof
+    ///
+    /// ```ignore
+    /// use tokio::net::unix::pipe;
+    ///
+    /// let tx = pipe::OpenOptions::new()
+    ///     .read_write(true)
+    ///     .open_receiver("path/to/a/fifo");
+    /// ```
+    #[cfg(target_os = "linux")]
+    #[cfg_attr(docsrs, doc(cfg(target_os = "linux")))]
+    pub fn read_write(&mut self, value: bool) -> &mut Self {
+        self.read_write = value;
+        self
+    }
+
+    /// Sets the option to skip the check for FIFO file type.
+    ///
+    /// By default, [`open_receiver`] and [`open_sender`] functions will check
+    /// if the opened file is a FIFO file. Set this option to `true` if you are
+    /// sure the file is a FIFO file.
+    ///
+    /// [`open_receiver`]: OpenOptions::open_receiver
+    /// [`open_sender`]: OpenOptions::open_sender
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use tokio::net::unix::pipe;
+    /// use nix::{unistd::mkfifo, sys::stat::Mode};
+    /// # use std::error::Error;
+    ///
+    /// // Our program has exclusive access to this path.
+    /// const FIFO_NAME: &str = "path/to/a/new/fifo";
+    ///
+    /// # async fn dox() -> Result<(), Box<dyn Error>> {
+    /// mkfifo(FIFO_NAME, Mode::S_IRWXU)?;
+    /// let rx = pipe::OpenOptions::new()
+    ///     .unchecked(true)
+    ///     .open_receiver(FIFO_NAME)?;
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn unchecked(&mut self, value: bool) -> &mut Self {
+        self.unchecked = value;
+        self
+    }
+
+    /// Creates a [`Receiver`] from a FIFO file with the options specified by `self`.
+    ///
+    /// This function will open the FIFO file at the specified path, possibly
+    /// check if it is a pipe, and associate the pipe with the default event
+    /// loop for reading.
+    ///
+    /// # Errors
+    ///
+    /// If the file type check fails, this function will fail with `io::ErrorKind::InvalidInput`.
+    /// This function may also fail with other standard OS errors.
+    ///
+    /// # Panics
+    ///
+    /// This function panics if it is not called from within a runtime with
+    /// IO enabled.
+    ///
+    /// The runtime is usually set implicitly when this function is called
+    /// from a future driven by a tokio runtime, otherwise runtime can be set
+    /// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter) function.
+    pub fn open_receiver<P: AsRef<Path>>(&self, path: P) -> io::Result<Receiver> {
+        let file = self.open(path.as_ref(), PipeEnd::Receiver)?;
+        Receiver::from_file_unchecked(file)
+    }
+
+    /// Creates a [`Sender`] from a FIFO file with the options specified by `self`.
+    ///
+    /// This function will open the FIFO file at the specified path, possibly
+    /// check if it is a pipe, and associate the pipe with the default event
+    /// loop for writing.
+    ///
+    /// # Errors
+    ///
+    /// If the file type check fails, this function will fail with `io::ErrorKind::InvalidInput`.
+    /// If the file is not opened in read-write access mode and the file is not
+    /// currently open for reading, this function will fail with `ENXIO`.
+    /// This function may also fail with other standard OS errors.
+    ///
+    /// # Panics
+    ///
+    /// This function panics if it is not called from within a runtime with
+    /// IO enabled.
+    ///
+    /// The runtime is usually set implicitly when this function is called
+    /// from a future driven by a tokio runtime, otherwise runtime can be set
+    /// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter) function.
+    pub fn open_sender<P: AsRef<Path>>(&self, path: P) -> io::Result<Sender> {
+        let file = self.open(path.as_ref(), PipeEnd::Sender)?;
+        Sender::from_file_unchecked(file)
+    }
+
+    fn open(&self, path: &Path, pipe_end: PipeEnd) -> io::Result<File> {
+        let mut options = std::fs::OpenOptions::new();
+        options
+            .read(pipe_end == PipeEnd::Receiver)
+            .write(pipe_end == PipeEnd::Sender)
+            .custom_flags(libc::O_NONBLOCK);
+
+        #[cfg(target_os = "linux")]
+        if self.read_write {
+            options.read(true).write(true);
+        }
+
+        let file = options.open(path)?;
+
+        if !self.unchecked && !is_fifo(&file)? {
+            return Err(io::Error::new(io::ErrorKind::InvalidInput, "not a pipe"));
+        }
+
+        Ok(file)
+    }
+}
+
+impl Default for OpenOptions {
+    fn default() -> OpenOptions {
+        OpenOptions::new()
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+enum PipeEnd {
+    Sender,
+    Receiver,
+}
+
+/// Writing end of a Unix pipe.
+///
+/// It can be constructed from a FIFO file with [`OpenOptions::open_sender`].
+///
+/// Opening a named pipe for writing involves a few steps.
+/// Call to [`OpenOptions::open_sender`] might fail with an error indicating
+/// different things:
+///
+/// * [`io::ErrorKind::NotFound`] - There is no file at the specified path.
+/// * [`io::ErrorKind::InvalidInput`] - The file exists, but it is not a FIFO.
+/// * [`ENXIO`] - The file is a FIFO, but no process has it open for reading.
+///   Sleep for a while and try again.
+/// * Other OS errors not specific to opening FIFO files.
+///
+/// Opening a `Sender` from a FIFO file should look like this:
+///
+/// ```no_run
+/// use tokio::net::unix::pipe;
+/// use tokio::time::{self, Duration};
+///
+/// const FIFO_NAME: &str = "path/to/a/fifo";
+///
+/// # async fn dox() -> Result<(), Box<dyn std::error::Error>> {
+/// // Wait for a reader to open the file.
+/// let tx = loop {
+///     match pipe::OpenOptions::new().open_sender(FIFO_NAME) {
+///         Ok(tx) => break tx,
+///         Err(e) if e.raw_os_error() == Some(libc::ENXIO) => {},
+///         Err(e) => return Err(e.into()),
+///     }
+///
+///     time::sleep(Duration::from_millis(50)).await;
+/// };
+/// # Ok(())
+/// # }
+/// ```
+///
+/// On Linux, it is possible to create a `Sender` without waiting in a sleeping
+/// loop. This is done by opening a named pipe in read-write access mode with
+/// `OpenOptions::read_write`. This way, a `Sender` can at the same time hold
+/// both a writing end and a reading end, and the latter allows to open a FIFO
+/// without [`ENXIO`] error since the pipe is open for reading as well.
+///
+/// `Sender` cannot be used to read from a pipe, so in practice the read access
+/// is only used when a FIFO is opened. However, using a `Sender` in read-write
+/// mode **may lead to lost data**, because written data will be dropped by the
+/// system as soon as all pipe ends are closed. To avoid lost data you have to
+/// make sure that a reading end has been opened before dropping a `Sender`.
+///
+/// Note that using read-write access mode with FIFO files is not defined by
+/// the POSIX standard and it is only guaranteed to work on Linux.
+///
+/// ```ignore
+/// use tokio::io::AsyncWriteExt;
+/// use tokio::net::unix::pipe;
+///
+/// const FIFO_NAME: &str = "path/to/a/fifo";
+///
+/// # async fn dox() -> Result<(), Box<dyn std::error::Error>> {
+/// let mut tx = pipe::OpenOptions::new()
+///     .read_write(true)
+///     .open_sender(FIFO_NAME)?;
+///
+/// // Asynchronously write to the pipe before a reader.
+/// tx.write_all(b"hello world").await?;
+/// # Ok(())
+/// # }
+/// ```
+///
+/// [`ENXIO`]: https://docs.rs/libc/latest/libc/constant.ENXIO.html
+#[derive(Debug)]
+pub struct Sender {
+    io: PollEvented<mio_pipe::Sender>,
+}
+
+impl Sender {
+    fn from_mio(mio_tx: mio_pipe::Sender) -> io::Result<Sender> {
+        let io = PollEvented::new_with_interest(mio_tx, Interest::WRITABLE)?;
+        Ok(Sender { io })
+    }
+
+    /// Creates a new `Sender` from a [`File`].
+    ///
+    /// This function is intended to construct a pipe from a [`File`] representing
+    /// a special FIFO file. It will check if the file is a pipe and has write access,
+    /// set it in non-blocking mode and perform the conversion.
+    ///
+    /// # Errors
+    ///
+    /// Fails with `io::ErrorKind::InvalidInput` if the file is not a pipe or it
+    /// does not have write access. Also fails with any standard OS error if it occurs.
+    ///
+    /// # Panics
+    ///
+    /// This function panics if it is not called from within a runtime with
+    /// IO enabled.
+    ///
+    /// The runtime is usually set implicitly when this function is called
+    /// from a future driven by a tokio runtime, otherwise runtime can be set
+    /// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter) function.
+    pub fn from_file(mut file: File) -> io::Result<Sender> {
+        if !is_fifo(&file)? {
+            return Err(io::Error::new(io::ErrorKind::InvalidInput, "not a pipe"));
+        }
+
+        let flags = get_file_flags(&file)?;
+        if has_write_access(flags) {
+            set_nonblocking(&mut file, flags)?;
+            Sender::from_file_unchecked(file)
+        } else {
+            Err(io::Error::new(
+                io::ErrorKind::InvalidInput,
+                "not in O_WRONLY or O_RDWR access mode",
+            ))
+        }
+    }
+
+    /// Creates a new `Sender` from a [`File`] without checking pipe properties.
+    ///
+    /// This function is intended to construct a pipe from a File representing
+    /// a special FIFO file. The conversion assumes nothing about the underlying
+    /// file; it is left up to the user to make sure it is opened with write access,
+    /// represents a pipe and is set in non-blocking mode.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use tokio::net::unix::pipe;
+    /// use std::fs::OpenOptions;
+    /// use std::os::unix::fs::{FileTypeExt, OpenOptionsExt};
+    /// # use std::error::Error;
+    ///
+    /// const FIFO_NAME: &str = "path/to/a/fifo";
+    ///
+    /// # async fn dox() -> Result<(), Box<dyn Error>> {
+    /// let file = OpenOptions::new()
+    ///     .write(true)
+    ///     .custom_flags(libc::O_NONBLOCK)
+    ///     .open(FIFO_NAME)?;
+    /// if file.metadata()?.file_type().is_fifo() {
+    ///     let tx = pipe::Sender::from_file_unchecked(file)?;
+    ///     /* use the Sender */
+    /// }
+    /// # Ok(())
+    /// # }
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if it is not called from within a runtime with
+    /// IO enabled.
+    ///
+    /// The runtime is usually set implicitly when this function is called
+    /// from a future driven by a tokio runtime, otherwise runtime can be set
+    /// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter) function.
+    pub fn from_file_unchecked(file: File) -> io::Result<Sender> {
+        let raw_fd = file.into_raw_fd();
+        let mio_tx = unsafe { mio_pipe::Sender::from_raw_fd(raw_fd) };
+        Sender::from_mio(mio_tx)
+    }
+
+    /// Waits for any of the requested ready states.
+    ///
+    /// This function can be used instead of [`writable()`] to check the returned
+    /// ready set for [`Ready::WRITABLE`] and [`Ready::WRITE_CLOSED`] events.
+    ///
+    /// The function may complete without the pipe being ready. This is a
+    /// false-positive and attempting an operation will return with
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
+    ///
+    /// [`writable()`]: Self::writable
+    ///
+    /// # Cancel safety
+    ///
+    /// This method is cancel safe. Once a readiness event occurs, the method
+    /// will continue to return immediately until the readiness event is
+    /// consumed by an attempt to write that fails with `WouldBlock` or
+    /// `Poll::Pending`.
+    pub async fn ready(&self, interest: Interest) -> io::Result<Ready> {
+        let event = self.io.registration().readiness(interest).await?;
+        Ok(event.ready)
+    }
+
+    /// Waits for the pipe to become writable.
+    ///
+    /// This function is equivalent to `ready(Interest::WRITABLE)` and is usually
+    /// paired with [`try_write()`].
+    ///
+    /// [`try_write()`]: Self::try_write
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use tokio::net::unix::pipe;
+    /// use std::io;
+    ///
+    /// #[tokio::main]
+    /// async fn main() -> io::Result<()> {
+    ///     // Open a writing end of a fifo
+    ///     let tx = pipe::OpenOptions::new().open_sender("path/to/a/fifo")?;
+    ///
+    ///     loop {
+    ///         // Wait for the pipe to be writable
+    ///         tx.writable().await?;
+    ///
+    ///         // Try to write data, this may still fail with `WouldBlock`
+    ///         // if the readiness event is a false positive.
+    ///         match tx.try_write(b"hello world") {
+    ///             Ok(n) => {
+    ///                 break;
+    ///             }
+    ///             Err(e) if e.kind() == io::ErrorKind::WouldBlock => {
+    ///                 continue;
+    ///             }
+    ///             Err(e) => {
+    ///                 return Err(e.into());
+    ///             }
+    ///         }
+    ///     }
+    ///
+    ///     Ok(())
+    /// }
+    /// ```
+    pub async fn writable(&self) -> io::Result<()> {
+        self.ready(Interest::WRITABLE).await?;
+        Ok(())
+    }
+
+    /// Polls for write readiness.
+    ///
+    /// If the pipe is not currently ready for writing, this method will
+    /// store a clone of the `Waker` from the provided `Context`. When the pipe
+    /// becomes ready for writing, `Waker::wake` will be called on the waker.
+    ///
+    /// Note that on multiple calls to `poll_write_ready` or `poll_write`, only
+    /// the `Waker` from the `Context` passed to the most recent call is
+    /// scheduled to receive a wakeup.
+    ///
+    /// This function is intended for cases where creating and pinning a future
+    /// via [`writable`] is not feasible. Where possible, using [`writable`] is
+    /// preferred, as this supports polling from multiple tasks at once.
+    ///
+    /// [`writable`]: Self::writable
+    ///
+    /// # Return value
+    ///
+    /// The function returns:
+    ///
+    /// * `Poll::Pending` if the pipe is not ready for writing.
+    /// * `Poll::Ready(Ok(()))` if the pipe is ready for writing.
+    /// * `Poll::Ready(Err(e))` if an error is encountered.
+    ///
+    /// # Errors
+    ///
+    /// This function may encounter any standard I/O error except `WouldBlock`.
+    pub fn poll_write_ready(&self, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        self.io.registration().poll_write_ready(cx).map_ok(|_| ())
+    }
+
+    /// Tries to write a buffer to the pipe, returning how many bytes were
+    /// written.
+    ///
+    /// The function will attempt to write the entire contents of `buf`, but
+    /// only part of the buffer may be written. If the length of `buf` is not
+    /// greater than `PIPE_BUF` (an OS constant, 4096 under Linux), then the
+    /// write is guaranteed to be atomic, i.e. either the entire content of
+    /// `buf` will be written or this method will fail with `WouldBlock`. There
+    /// is no such guarantee if `buf` is larger than `PIPE_BUF`.
+    ///
+    /// This function is usually paired with [`writable`].
+    ///
+    /// [`writable`]: Self::writable
+    ///
+    /// # Return
+    ///
+    /// If data is successfully written, `Ok(n)` is returned, where `n` is the
+    /// number of bytes written. If the pipe is not ready to write data,
+    /// `Err(io::ErrorKind::WouldBlock)` is returned.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use tokio::net::unix::pipe;
+    /// use std::io;
+    ///
+    /// #[tokio::main]
+    /// async fn main() -> io::Result<()> {
+    ///     // Open a writing end of a fifo
+    ///     let tx = pipe::OpenOptions::new().open_sender("path/to/a/fifo")?;
+    ///
+    ///     loop {
+    ///         // Wait for the pipe to be writable
+    ///         tx.writable().await?;
+    ///
+    ///         // Try to write data, this may still fail with `WouldBlock`
+    ///         // if the readiness event is a false positive.
+    ///         match tx.try_write(b"hello world") {
+    ///             Ok(n) => {
+    ///                 break;
+    ///             }
+    ///             Err(e) if e.kind() == io::ErrorKind::WouldBlock => {
+    ///                 continue;
+    ///             }
+    ///             Err(e) => {
+    ///                 return Err(e.into());
+    ///             }
+    ///         }
+    ///     }
+    ///
+    ///     Ok(())
+    /// }
+    /// ```
+    pub fn try_write(&self, buf: &[u8]) -> io::Result<usize> {
+        self.io
+            .registration()
+            .try_io(Interest::WRITABLE, || (&*self.io).write(buf))
+    }
+
+    /// Tries to write several buffers to the pipe, returning how many bytes
+    /// were written.
+    ///
+    /// Data is written from each buffer in order, with the final buffer read
+    /// from possible being only partially consumed. This method behaves
+    /// equivalently to a single call to [`try_write()`] with concatenated
+    /// buffers.
+    ///
+    /// If the total length of buffers is not greater than `PIPE_BUF` (an OS
+    /// constant, 4096 under Linux), then the write is guaranteed to be atomic,
+    /// i.e. either the entire contents of buffers will be written or this
+    /// method will fail with `WouldBlock`. There is no such guarantee if the
+    /// total length of buffers is greater than `PIPE_BUF`.
+    ///
+    /// This function is usually paired with [`writable`].
+    ///
+    /// [`try_write()`]: Self::try_write()
+    /// [`writable`]: Self::writable
+    ///
+    /// # Return
+    ///
+    /// If data is successfully written, `Ok(n)` is returned, where `n` is the
+    /// number of bytes written. If the pipe is not ready to write data,
+    /// `Err(io::ErrorKind::WouldBlock)` is returned.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use tokio::net::unix::pipe;
+    /// use std::io;
+    ///
+    /// #[tokio::main]
+    /// async fn main() -> io::Result<()> {
+    ///     // Open a writing end of a fifo
+    ///     let tx = pipe::OpenOptions::new().open_sender("path/to/a/fifo")?;
+    ///
+    ///     let bufs = [io::IoSlice::new(b"hello "), io::IoSlice::new(b"world")];
+    ///
+    ///     loop {
+    ///         // Wait for the pipe to be writable
+    ///         tx.writable().await?;
+    ///
+    ///         // Try to write data, this may still fail with `WouldBlock`
+    ///         // if the readiness event is a false positive.
+    ///         match tx.try_write_vectored(&bufs) {
+    ///             Ok(n) => {
+    ///                 break;
+    ///             }
+    ///             Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
+    ///                 continue;
+    ///             }
+    ///             Err(e) => {
+    ///                 return Err(e.into());
+    ///             }
+    ///         }
+    ///     }
+    ///
+    ///     Ok(())
+    /// }
+    /// ```
+    pub fn try_write_vectored(&self, buf: &[io::IoSlice<'_>]) -> io::Result<usize> {
+        self.io
+            .registration()
+            .try_io(Interest::WRITABLE, || (&*self.io).write_vectored(buf))
+    }
+}
+
+impl AsyncWrite for Sender {
+    fn poll_write(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        self.io.poll_write(cx, buf)
+    }
+
+    fn poll_write_vectored(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        bufs: &[io::IoSlice<'_>],
+    ) -> Poll<io::Result<usize>> {
+        self.io.poll_write_vectored(cx, bufs)
+    }
+
+    fn is_write_vectored(&self) -> bool {
+        true
+    }
+
+    fn poll_flush(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Poll::Ready(Ok(()))
+    }
+
+    fn poll_shutdown(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Poll::Ready(Ok(()))
+    }
+}
+
+impl AsRawFd for Sender {
+    fn as_raw_fd(&self) -> RawFd {
+        self.io.as_raw_fd()
+    }
+}
+
+/// Reading end of a Unix pipe.
+///
+/// It can be constructed from a FIFO file with [`OpenOptions::open_receiver`].
+///
+/// # Examples
+///
+/// Receiving messages from a named pipe in a loop:
+///
+/// ```no_run
+/// use tokio::net::unix::pipe;
+/// use tokio::io::{self, AsyncReadExt};
+///
+/// const FIFO_NAME: &str = "path/to/a/fifo";
+///
+/// # async fn dox() -> Result<(), Box<dyn std::error::Error>> {
+/// let mut rx = pipe::OpenOptions::new().open_receiver(FIFO_NAME)?;
+/// loop {
+///     let mut msg = vec![0; 256];
+///     match rx.read_exact(&mut msg).await {
+///         Ok(_) => {
+///             /* handle the message */
+///         }
+///         Err(e) if e.kind() == io::ErrorKind::UnexpectedEof => {
+///             // Writing end has been closed, we should reopen the pipe.
+///             rx = pipe::OpenOptions::new().open_receiver(FIFO_NAME)?;
+///         }
+///         Err(e) => return Err(e.into()),
+///     }
+/// }
+/// # }
+/// ```
+///
+/// On Linux, you can use a `Receiver` in read-write access mode to implement
+/// resilient reading from a named pipe. Unlike `Receiver` opened in read-only
+/// mode, read from a pipe in read-write mode will not fail with `UnexpectedEof`
+/// when the writing end is closed. This way, a `Receiver` can asynchronously
+/// wait for the next writer to open the pipe.
+///
+/// You should not use functions waiting for EOF such as [`read_to_end`] with
+/// a `Receiver` in read-write access mode, since it **may wait forever**.
+/// `Receiver` in this mode also holds an open writing end, which prevents
+/// receiving EOF.
+///
+/// To set the read-write access mode you can use `OpenOptions::read_write`.
+/// Note that using read-write access mode with FIFO files is not defined by
+/// the POSIX standard and it is only guaranteed to work on Linux.
+///
+/// ```ignore
+/// use tokio::net::unix::pipe;
+/// use tokio::io::AsyncReadExt;
+/// # use std::error::Error;
+///
+/// const FIFO_NAME: &str = "path/to/a/fifo";
+///
+/// # async fn dox() -> Result<(), Box<dyn Error>> {
+/// let mut rx = pipe::OpenOptions::new()
+///     .read_write(true)
+///     .open_receiver(FIFO_NAME)?;
+/// loop {
+///     let mut msg = vec![0; 256];
+///     rx.read_exact(&mut msg).await?;
+///     /* handle the message */
+/// }
+/// # }
+/// ```
+///
+/// [`read_to_end`]: crate::io::AsyncReadExt::read_to_end
+#[derive(Debug)]
+pub struct Receiver {
+    io: PollEvented<mio_pipe::Receiver>,
+}
+
+impl Receiver {
+    fn from_mio(mio_rx: mio_pipe::Receiver) -> io::Result<Receiver> {
+        let io = PollEvented::new_with_interest(mio_rx, Interest::READABLE)?;
+        Ok(Receiver { io })
+    }
+
+    /// Creates a new `Receiver` from a [`File`].
+    ///
+    /// This function is intended to construct a pipe from a [`File`] representing
+    /// a special FIFO file. It will check if the file is a pipe and has read access,
+    /// set it in non-blocking mode and perform the conversion.
+    ///
+    /// # Errors
+    ///
+    /// Fails with `io::ErrorKind::InvalidInput` if the file is not a pipe or it
+    /// does not have read access. Also fails with any standard OS error if it occurs.
+    ///
+    /// # Panics
+    ///
+    /// This function panics if it is not called from within a runtime with
+    /// IO enabled.
+    ///
+    /// The runtime is usually set implicitly when this function is called
+    /// from a future driven by a tokio runtime, otherwise runtime can be set
+    /// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter) function.
+    pub fn from_file(mut file: File) -> io::Result<Receiver> {
+        if !is_fifo(&file)? {
+            return Err(io::Error::new(io::ErrorKind::InvalidInput, "not a pipe"));
+        }
+
+        let flags = get_file_flags(&file)?;
+        if has_read_access(flags) {
+            set_nonblocking(&mut file, flags)?;
+            Receiver::from_file_unchecked(file)
+        } else {
+            Err(io::Error::new(
+                io::ErrorKind::InvalidInput,
+                "not in O_RDONLY or O_RDWR access mode",
+            ))
+        }
+    }
+
+    /// Creates a new `Receiver` from a [`File`] without checking pipe properties.
+    ///
+    /// This function is intended to construct a pipe from a File representing
+    /// a special FIFO file. The conversion assumes nothing about the underlying
+    /// file; it is left up to the user to make sure it is opened with read access,
+    /// represents a pipe and is set in non-blocking mode.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use tokio::net::unix::pipe;
+    /// use std::fs::OpenOptions;
+    /// use std::os::unix::fs::{FileTypeExt, OpenOptionsExt};
+    /// # use std::error::Error;
+    ///
+    /// const FIFO_NAME: &str = "path/to/a/fifo";
+    ///
+    /// # async fn dox() -> Result<(), Box<dyn Error>> {
+    /// let file = OpenOptions::new()
+    ///     .read(true)
+    ///     .custom_flags(libc::O_NONBLOCK)
+    ///     .open(FIFO_NAME)?;
+    /// if file.metadata()?.file_type().is_fifo() {
+    ///     let rx = pipe::Receiver::from_file_unchecked(file)?;
+    ///     /* use the Receiver */
+    /// }
+    /// # Ok(())
+    /// # }
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if it is not called from within a runtime with
+    /// IO enabled.
+    ///
+    /// The runtime is usually set implicitly when this function is called
+    /// from a future driven by a tokio runtime, otherwise runtime can be set
+    /// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter) function.
+    pub fn from_file_unchecked(file: File) -> io::Result<Receiver> {
+        let raw_fd = file.into_raw_fd();
+        let mio_rx = unsafe { mio_pipe::Receiver::from_raw_fd(raw_fd) };
+        Receiver::from_mio(mio_rx)
+    }
+
+    /// Waits for any of the requested ready states.
+    ///
+    /// This function can be used instead of [`readable()`] to check the returned
+    /// ready set for [`Ready::READABLE`] and [`Ready::READ_CLOSED`] events.
+    ///
+    /// The function may complete without the pipe being ready. This is a
+    /// false-positive and attempting an operation will return with
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
+    ///
+    /// [`readable()`]: Self::readable
+    ///
+    /// # Cancel safety
+    ///
+    /// This method is cancel safe. Once a readiness event occurs, the method
+    /// will continue to return immediately until the readiness event is
+    /// consumed by an attempt to read that fails with `WouldBlock` or
+    /// `Poll::Pending`.
+    pub async fn ready(&self, interest: Interest) -> io::Result<Ready> {
+        let event = self.io.registration().readiness(interest).await?;
+        Ok(event.ready)
+    }
+
+    /// Waits for the pipe to become readable.
+    ///
+    /// This function is equivalent to `ready(Interest::READABLE)` and is usually
+    /// paired with [`try_read()`].
+    ///
+    /// [`try_read()`]: Self::try_read()
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use tokio::net::unix::pipe;
+    /// use std::io;
+    ///
+    /// #[tokio::main]
+    /// async fn main() -> io::Result<()> {
+    ///     // Open a reading end of a fifo
+    ///     let rx = pipe::OpenOptions::new().open_receiver("path/to/a/fifo")?;
+    ///
+    ///     let mut msg = vec![0; 1024];
+    ///
+    ///     loop {
+    ///         // Wait for the pipe to be readable
+    ///         rx.readable().await?;
+    ///
+    ///         // Try to read data, this may still fail with `WouldBlock`
+    ///         // if the readiness event is a false positive.
+    ///         match rx.try_read(&mut msg) {
+    ///             Ok(n) => {
+    ///                 msg.truncate(n);
+    ///                 break;
+    ///             }
+    ///             Err(e) if e.kind() == io::ErrorKind::WouldBlock => {
+    ///                 continue;
+    ///             }
+    ///             Err(e) => {
+    ///                 return Err(e.into());
+    ///             }
+    ///         }
+    ///     }
+    ///
+    ///     println!("GOT = {:?}", msg);
+    ///     Ok(())
+    /// }
+    /// ```
+    pub async fn readable(&self) -> io::Result<()> {
+        self.ready(Interest::READABLE).await?;
+        Ok(())
+    }
+
+    /// Polls for read readiness.
+    ///
+    /// If the pipe is not currently ready for reading, this method will
+    /// store a clone of the `Waker` from the provided `Context`. When the pipe
+    /// becomes ready for reading, `Waker::wake` will be called on the waker.
+    ///
+    /// Note that on multiple calls to `poll_read_ready` or `poll_read`, only
+    /// the `Waker` from the `Context` passed to the most recent call is
+    /// scheduled to receive a wakeup.
+    ///
+    /// This function is intended for cases where creating and pinning a future
+    /// via [`readable`] is not feasible. Where possible, using [`readable`] is
+    /// preferred, as this supports polling from multiple tasks at once.
+    ///
+    /// [`readable`]: Self::readable
+    ///
+    /// # Return value
+    ///
+    /// The function returns:
+    ///
+    /// * `Poll::Pending` if the pipe is not ready for reading.
+    /// * `Poll::Ready(Ok(()))` if the pipe is ready for reading.
+    /// * `Poll::Ready(Err(e))` if an error is encountered.
+    ///
+    /// # Errors
+    ///
+    /// This function may encounter any standard I/O error except `WouldBlock`.
+    pub fn poll_read_ready(&self, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        self.io.registration().poll_read_ready(cx).map_ok(|_| ())
+    }
+
+    /// Tries to read data from the pipe into the provided buffer, returning how
+    /// many bytes were read.
+    ///
+    /// Reads any pending data from the pipe but does not wait for new data
+    /// to arrive. On success, returns the number of bytes read. Because
+    /// `try_read()` is non-blocking, the buffer does not have to be stored by
+    /// the async task and can exist entirely on the stack.
+    ///
+    /// Usually [`readable()`] is used with this function.
+    ///
+    /// [`readable()`]: Self::readable()
+    ///
+    /// # Return
+    ///
+    /// If data is successfully read, `Ok(n)` is returned, where `n` is the
+    /// number of bytes read. If `n` is `0`, then it can indicate one of two scenarios:
+    ///
+    /// 1. The pipe's writing end is closed and will no longer write data.
+    /// 2. The specified buffer was 0 bytes in length.
+    ///
+    /// If the pipe is not ready to read data,
+    /// `Err(io::ErrorKind::WouldBlock)` is returned.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use tokio::net::unix::pipe;
+    /// use std::io;
+    ///
+    /// #[tokio::main]
+    /// async fn main() -> io::Result<()> {
+    ///     // Open a reading end of a fifo
+    ///     let rx = pipe::OpenOptions::new().open_receiver("path/to/a/fifo")?;
+    ///
+    ///     let mut msg = vec![0; 1024];
+    ///
+    ///     loop {
+    ///         // Wait for the pipe to be readable
+    ///         rx.readable().await?;
+    ///
+    ///         // Try to read data, this may still fail with `WouldBlock`
+    ///         // if the readiness event is a false positive.
+    ///         match rx.try_read(&mut msg) {
+    ///             Ok(n) => {
+    ///                 msg.truncate(n);
+    ///                 break;
+    ///             }
+    ///             Err(e) if e.kind() == io::ErrorKind::WouldBlock => {
+    ///                 continue;
+    ///             }
+    ///             Err(e) => {
+    ///                 return Err(e.into());
+    ///             }
+    ///         }
+    ///     }
+    ///
+    ///     println!("GOT = {:?}", msg);
+    ///     Ok(())
+    /// }
+    /// ```
+    pub fn try_read(&self, buf: &mut [u8]) -> io::Result<usize> {
+        self.io
+            .registration()
+            .try_io(Interest::READABLE, || (&*self.io).read(buf))
+    }
+
+    /// Tries to read data from the pipe into the provided buffers, returning
+    /// how many bytes were read.
+    ///
+    /// Data is copied to fill each buffer in order, with the final buffer
+    /// written to possibly being only partially filled. This method behaves
+    /// equivalently to a single call to [`try_read()`] with concatenated
+    /// buffers.
+    ///
+    /// Reads any pending data from the pipe but does not wait for new data
+    /// to arrive. On success, returns the number of bytes read. Because
+    /// `try_read_vectored()` is non-blocking, the buffer does not have to be
+    /// stored by the async task and can exist entirely on the stack.
+    ///
+    /// Usually, [`readable()`] is used with this function.
+    ///
+    /// [`try_read()`]: Self::try_read()
+    /// [`readable()`]: Self::readable()
+    ///
+    /// # Return
+    ///
+    /// If data is successfully read, `Ok(n)` is returned, where `n` is the
+    /// number of bytes read. `Ok(0)` indicates the pipe's writing end is
+    /// closed and will no longer write data. If the pipe is not ready to read
+    /// data `Err(io::ErrorKind::WouldBlock)` is returned.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use tokio::net::unix::pipe;
+    /// use std::io;
+    ///
+    /// #[tokio::main]
+    /// async fn main() -> io::Result<()> {
+    ///     // Open a reading end of a fifo
+    ///     let rx = pipe::OpenOptions::new().open_receiver("path/to/a/fifo")?;
+    ///
+    ///     loop {
+    ///         // Wait for the pipe to be readable
+    ///         rx.readable().await?;
+    ///
+    ///         // Creating the buffer **after** the `await` prevents it from
+    ///         // being stored in the async task.
+    ///         let mut buf_a = [0; 512];
+    ///         let mut buf_b = [0; 1024];
+    ///         let mut bufs = [
+    ///             io::IoSliceMut::new(&mut buf_a),
+    ///             io::IoSliceMut::new(&mut buf_b),
+    ///         ];
+    ///
+    ///         // Try to read data, this may still fail with `WouldBlock`
+    ///         // if the readiness event is a false positive.
+    ///         match rx.try_read_vectored(&mut bufs) {
+    ///             Ok(0) => break,
+    ///             Ok(n) => {
+    ///                 println!("read {} bytes", n);
+    ///             }
+    ///             Err(e) if e.kind() == io::ErrorKind::WouldBlock => {
+    ///                 continue;
+    ///             }
+    ///             Err(e) => {
+    ///                 return Err(e.into());
+    ///             }
+    ///         }
+    ///     }
+    ///
+    ///     Ok(())
+    /// }
+    /// ```
+    pub fn try_read_vectored(&self, bufs: &mut [io::IoSliceMut<'_>]) -> io::Result<usize> {
+        self.io
+            .registration()
+            .try_io(Interest::READABLE, || (&*self.io).read_vectored(bufs))
+    }
+
+    cfg_io_util! {
+        /// Tries to read data from the pipe into the provided buffer, advancing the
+        /// buffer's internal cursor, returning how many bytes were read.
+        ///
+        /// Reads any pending data from the pipe but does not wait for new data
+        /// to arrive. On success, returns the number of bytes read. Because
+        /// `try_read_buf()` is non-blocking, the buffer does not have to be stored by
+        /// the async task and can exist entirely on the stack.
+        ///
+        /// Usually, [`readable()`] or [`ready()`] is used with this function.
+        ///
+        /// [`readable()`]: Self::readable
+        /// [`ready()`]: Self::ready
+        ///
+        /// # Return
+        ///
+        /// If data is successfully read, `Ok(n)` is returned, where `n` is the
+        /// number of bytes read. `Ok(0)` indicates the pipe's writing end is
+        /// closed and will no longer write data. If the pipe is not ready to read
+        /// data `Err(io::ErrorKind::WouldBlock)` is returned.
+        ///
+        /// # Examples
+        ///
+        /// ```no_run
+        /// use tokio::net::unix::pipe;
+        /// use std::io;
+        ///
+        /// #[tokio::main]
+        /// async fn main() -> io::Result<()> {
+        ///     // Open a reading end of a fifo
+        ///     let rx = pipe::OpenOptions::new().open_receiver("path/to/a/fifo")?;
+        ///
+        ///     loop {
+        ///         // Wait for the pipe to be readable
+        ///         rx.readable().await?;
+        ///
+        ///         let mut buf = Vec::with_capacity(4096);
+        ///
+        ///         // Try to read data, this may still fail with `WouldBlock`
+        ///         // if the readiness event is a false positive.
+        ///         match rx.try_read_buf(&mut buf) {
+        ///             Ok(0) => break,
+        ///             Ok(n) => {
+        ///                 println!("read {} bytes", n);
+        ///             }
+        ///             Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
+        ///                 continue;
+        ///             }
+        ///             Err(e) => {
+        ///                 return Err(e.into());
+        ///             }
+        ///         }
+        ///     }
+        ///
+        ///     Ok(())
+        /// }
+        /// ```
+        pub fn try_read_buf<B: BufMut>(&self, buf: &mut B) -> io::Result<usize> {
+            self.io.registration().try_io(Interest::READABLE, || {
+                use std::io::Read;
+
+                let dst = buf.chunk_mut();
+                let dst =
+                    unsafe { &mut *(dst as *mut _ as *mut [std::mem::MaybeUninit<u8>] as *mut [u8]) };
+
+                // Safety: `mio_pipe::Receiver` uses a `std::fs::File` underneath,
+                // which correctly handles reads into uninitialized memory.
+                let n = (&*self.io).read(dst)?;
+
+                unsafe {
+                    buf.advance_mut(n);
+                }
+
+                Ok(n)
+            })
+        }
+    }
+}
+
+impl AsyncRead for Receiver {
+    fn poll_read(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<io::Result<()>> {
+        // Safety: `mio_pipe::Receiver` uses a `std::fs::File` underneath,
+        // which correctly handles reads into uninitialized memory.
+        unsafe { self.io.poll_read(cx, buf) }
+    }
+}
+
+impl AsRawFd for Receiver {
+    fn as_raw_fd(&self) -> RawFd {
+        self.io.as_raw_fd()
+    }
+}
+
+/// Checks if file is a FIFO
+fn is_fifo(file: &File) -> io::Result<bool> {
+    Ok(file.metadata()?.file_type().is_fifo())
+}
+
+/// Gets file descriptor's flags by fcntl.
+fn get_file_flags(file: &File) -> io::Result<libc::c_int> {
+    let fd = file.as_raw_fd();
+    let flags = unsafe { libc::fcntl(fd, libc::F_GETFL) };
+    if flags < 0 {
+        Err(io::Error::last_os_error())
+    } else {
+        Ok(flags)
+    }
+}
+
+/// Checks for O_RDONLY or O_RDWR access mode.
+fn has_read_access(flags: libc::c_int) -> bool {
+    let mode = flags & libc::O_ACCMODE;
+    mode == libc::O_RDONLY || mode == libc::O_RDWR
+}
+
+/// Checks for O_WRONLY or O_RDWR access mode.
+fn has_write_access(flags: libc::c_int) -> bool {
+    let mode = flags & libc::O_ACCMODE;
+    mode == libc::O_WRONLY || mode == libc::O_RDWR
+}
+
+/// Sets file's flags with O_NONBLOCK by fcntl.
+fn set_nonblocking(file: &mut File, current_flags: libc::c_int) -> io::Result<()> {
+    let fd = file.as_raw_fd();
+
+    let flags = current_flags | libc::O_NONBLOCK;
+
+    if flags != current_flags {
+        let ret = unsafe { libc::fcntl(fd, libc::F_SETFL, flags) };
+        if ret < 0 {
+            return Err(io::Error::last_os_error());
+        }
+    }
+
+    Ok(())
+}
diff --git a/tokio/src/net/unix/split.rs b/tokio/src/net/unix/split.rs
index f9664d53254..816a2578b5f 100644
--- a/tokio/src/net/unix/split.rs
+++ b/tokio/src/net/unix/split.rs
@@ -182,6 +182,12 @@ impl WriteHalf<'_> {
     /// can be used to concurrently read / write to the same socket on a single
     /// task without splitting the socket.
     ///
+    /// The function may complete without the socket being ready. This is a
+    /// false-positive and attempting an operation will return with
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
+    ///
     /// # Cancel safety
     ///
     /// This method is cancel safe. Once a readiness event occurs, the method
diff --git a/tokio/src/net/unix/split_owned.rs b/tokio/src/net/unix/split_owned.rs
index 3dce2a86aa8..2cb561d4bd0 100644
--- a/tokio/src/net/unix/split_owned.rs
+++ b/tokio/src/net/unix/split_owned.rs
@@ -114,6 +114,12 @@ impl OwnedReadHalf {
     /// can be used to concurrently read / write to the same socket on a single
     /// task without splitting the socket.
     ///
+    /// The function may complete without the socket being ready. This is a
+    /// false-positive and attempting an operation will return with
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
+    ///
     /// # Cancel safety
     ///
     /// This method is cancel safe. Once a readiness event occurs, the method
@@ -265,6 +271,12 @@ impl OwnedWriteHalf {
     /// can be used to concurrently read / write to the same socket on a single
     /// task without splitting the socket.
     ///
+    /// The function may complete without the socket being ready. This is a
+    /// false-positive and attempting an operation will return with
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
+    ///
     /// # Cancel safety
     ///
     /// This method is cancel safe. Once a readiness event occurs, the method
@@ -386,12 +398,12 @@ impl AsyncWrite for OwnedWriteHalf {
 
 impl AsRef<UnixStream> for OwnedReadHalf {
     fn as_ref(&self) -> &UnixStream {
-        &*self.inner
+        &self.inner
     }
 }
 
 impl AsRef<UnixStream> for OwnedWriteHalf {
     fn as_ref(&self) -> &UnixStream {
-        &*self.inner
+        &self.inner
     }
 }
diff --git a/tokio/src/net/unix/stream.rs b/tokio/src/net/unix/stream.rs
index f0a7e37554c..529f10f33d4 100644
--- a/tokio/src/net/unix/stream.rs
+++ b/tokio/src/net/unix/stream.rs
@@ -66,6 +66,12 @@ impl UnixStream {
     /// can be used to concurrently read / write to the same socket on a single
     /// task without splitting the socket.
     ///
+    /// The function may complete without the socket being ready. This is a
+    /// false-positive and attempting an operation will return with
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
+    ///
     /// # Cancel safety
     ///
     /// This method is cancel safe. Once a readiness event occurs, the method
@@ -745,9 +751,31 @@ impl UnixStream {
     /// Creates new `UnixStream` from a `std::os::unix::net::UnixStream`.
     ///
     /// This function is intended to be used to wrap a UnixStream from the
-    /// standard library in the Tokio equivalent. The conversion assumes
-    /// nothing about the underlying stream; it is left up to the user to set
-    /// it in non-blocking mode.
+    /// standard library in the Tokio equivalent.
+    ///
+    /// # Notes
+    ///
+    /// The caller is responsible for ensuring that the stream is in
+    /// non-blocking mode. Otherwise all I/O operations on the stream
+    /// will block the thread, which will cause unexpected behavior.
+    /// Non-blocking mode can be set using [`set_nonblocking`].
+    ///
+    /// [`set_nonblocking`]: std::os::unix::net::UnixStream::set_nonblocking
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use tokio::net::UnixStream;
+    /// use std::os::unix::net::UnixStream as StdUnixStream;
+    /// # use std::error::Error;
+    ///
+    /// # async fn dox() -> Result<(), Box<dyn Error>> {
+    /// let std_stream = StdUnixStream::connect("/path/to/the/socket")?;
+    /// std_stream.set_nonblocking(true)?;
+    /// let stream = UnixStream::from_std(std_stream)?;
+    /// # Ok(())
+    /// # }
+    /// ```
     ///
     /// # Panics
     ///
diff --git a/tokio/src/net/windows/named_pipe.rs b/tokio/src/net/windows/named_pipe.rs
index 477c1057714..19325bfabad 100644
--- a/tokio/src/net/windows/named_pipe.rs
+++ b/tokio/src/net/windows/named_pipe.rs
@@ -238,6 +238,12 @@ impl NamedPipeServer {
     /// can be used to concurrently read / write to the same pipe on a single
     /// task without splitting the pipe.
     ///
+    /// The function may complete without the pipe being ready. This is a
+    /// false-positive and attempting an operation will return with
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
+    ///
     /// # Examples
     ///
     /// Concurrently read and write to the pipe on the same task without
@@ -1031,6 +1037,12 @@ impl NamedPipeClient {
     /// can be used to concurrently read / write to the same pipe on a single
     /// task without splitting the pipe.
     ///
+    /// The function may complete without the pipe being ready. This is a
+    /// false-positive and attempting an operation will return with
+    /// `io::ErrorKind::WouldBlock`. The function can also return with an empty
+    /// [`Ready`] set, so you should always check the returned value and possibly
+    /// wait again if the requested states are not set.
+    ///
     /// # Examples
     ///
     /// Concurrently read and write to the pipe on the same task without
@@ -1717,19 +1729,6 @@ impl AsRawHandle for NamedPipeClient {
     }
 }
 
-// Helper to set a boolean flag as a bitfield.
-macro_rules! bool_flag {
-    ($f:expr, $t:expr, $flag:expr) => {{
-        let current = $f;
-
-        if $t {
-            $f = current | $flag;
-        } else {
-            $f = current & !$flag;
-        };
-    }};
-}
-
 /// A builder structure for construct a named pipe with named pipe-specific
 /// options. This is required to use for named pipe servers who wants to modify
 /// pipe-related options.
@@ -1737,8 +1736,17 @@ macro_rules! bool_flag {
 /// See [`ServerOptions::create`].
 #[derive(Debug, Clone)]
 pub struct ServerOptions {
-    open_mode: u32,
-    pipe_mode: u32,
+    // dwOpenMode
+    access_inbound: bool,
+    access_outbound: bool,
+    first_pipe_instance: bool,
+    write_dac: bool,
+    write_owner: bool,
+    access_system_security: bool,
+    // dwPipeMode
+    pipe_mode: PipeMode,
+    reject_remote_clients: bool,
+    // other options
     max_instances: u32,
     out_buffer_size: u32,
     in_buffer_size: u32,
@@ -1759,8 +1767,14 @@ impl ServerOptions {
     /// ```
     pub fn new() -> ServerOptions {
         ServerOptions {
-            open_mode: windows_sys::PIPE_ACCESS_DUPLEX | windows_sys::FILE_FLAG_OVERLAPPED,
-            pipe_mode: windows_sys::PIPE_TYPE_BYTE | windows_sys::PIPE_REJECT_REMOTE_CLIENTS,
+            access_inbound: true,
+            access_outbound: true,
+            first_pipe_instance: false,
+            write_dac: false,
+            write_owner: false,
+            access_system_security: false,
+            pipe_mode: PipeMode::Byte,
+            reject_remote_clients: true,
             max_instances: windows_sys::PIPE_UNLIMITED_INSTANCES,
             out_buffer_size: 65536,
             in_buffer_size: 65536,
@@ -1773,15 +1787,11 @@ impl ServerOptions {
     /// The default pipe mode is [`PipeMode::Byte`]. See [`PipeMode`] for
     /// documentation of what each mode means.
     ///
-    /// This corresponding to specifying [`dwPipeMode`].
+    /// This corresponds to specifying `PIPE_TYPE_` and `PIPE_READMODE_` in  [`dwPipeMode`].
     ///
     /// [`dwPipeMode`]: https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-createnamedpipea
     pub fn pipe_mode(&mut self, pipe_mode: PipeMode) -> &mut Self {
-        self.pipe_mode = match pipe_mode {
-            PipeMode::Byte => windows_sys::PIPE_TYPE_BYTE,
-            PipeMode::Message => windows_sys::PIPE_TYPE_MESSAGE,
-        };
-
+        self.pipe_mode = pipe_mode;
         self
     }
 
@@ -1877,7 +1887,7 @@ impl ServerOptions {
     /// # Ok(()) }
     /// ```
     pub fn access_inbound(&mut self, allowed: bool) -> &mut Self {
-        bool_flag!(self.open_mode, allowed, windows_sys::PIPE_ACCESS_INBOUND);
+        self.access_inbound = allowed;
         self
     }
 
@@ -1975,7 +1985,7 @@ impl ServerOptions {
     /// # Ok(()) }
     /// ```
     pub fn access_outbound(&mut self, allowed: bool) -> &mut Self {
-        bool_flag!(self.open_mode, allowed, windows_sys::PIPE_ACCESS_OUTBOUND);
+        self.access_outbound = allowed;
         self
     }
 
@@ -2043,11 +2053,7 @@ impl ServerOptions {
     /// [`create`]: ServerOptions::create
     /// [`FILE_FLAG_FIRST_PIPE_INSTANCE`]: https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-createnamedpipea#pipe_first_pipe_instance
     pub fn first_pipe_instance(&mut self, first: bool) -> &mut Self {
-        bool_flag!(
-            self.open_mode,
-            first,
-            windows_sys::FILE_FLAG_FIRST_PIPE_INSTANCE
-        );
+        self.first_pipe_instance = first;
         self
     }
 
@@ -2129,7 +2135,7 @@ impl ServerOptions {
     ///
     /// [`WRITE_DAC`]: https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-createnamedpipea
     pub fn write_dac(&mut self, requested: bool) -> &mut Self {
-        bool_flag!(self.open_mode, requested, windows_sys::WRITE_DAC);
+        self.write_dac = requested;
         self
     }
 
@@ -2139,7 +2145,7 @@ impl ServerOptions {
     ///
     /// [`WRITE_OWNER`]: https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-createnamedpipea
     pub fn write_owner(&mut self, requested: bool) -> &mut Self {
-        bool_flag!(self.open_mode, requested, windows_sys::WRITE_OWNER);
+        self.write_owner = requested;
         self
     }
 
@@ -2149,11 +2155,7 @@ impl ServerOptions {
     ///
     /// [`ACCESS_SYSTEM_SECURITY`]: https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-createnamedpipea
     pub fn access_system_security(&mut self, requested: bool) -> &mut Self {
-        bool_flag!(
-            self.open_mode,
-            requested,
-            windows_sys::ACCESS_SYSTEM_SECURITY
-        );
+        self.access_system_security = requested;
         self
     }
 
@@ -2164,11 +2166,7 @@ impl ServerOptions {
     ///
     /// [`PIPE_REJECT_REMOTE_CLIENTS`]: https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-createnamedpipea#pipe_reject_remote_clients
     pub fn reject_remote_clients(&mut self, reject: bool) -> &mut Self {
-        bool_flag!(
-            self.pipe_mode,
-            reject,
-            windows_sys::PIPE_REJECT_REMOTE_CLIENTS
-        );
+        self.reject_remote_clients = reject;
         self
     }
 
@@ -2314,10 +2312,46 @@ impl ServerOptions {
     ) -> io::Result<NamedPipeServer> {
         let addr = encode_addr(addr);
 
+        let pipe_mode = {
+            let mut mode = if matches!(self.pipe_mode, PipeMode::Message) {
+                windows_sys::PIPE_TYPE_MESSAGE | windows_sys::PIPE_READMODE_MESSAGE
+            } else {
+                windows_sys::PIPE_TYPE_BYTE | windows_sys::PIPE_READMODE_BYTE
+            };
+            if self.reject_remote_clients {
+                mode |= windows_sys::PIPE_REJECT_REMOTE_CLIENTS;
+            } else {
+                mode |= windows_sys::PIPE_ACCEPT_REMOTE_CLIENTS;
+            }
+            mode
+        };
+        let open_mode = {
+            let mut mode = windows_sys::FILE_FLAG_OVERLAPPED;
+            if self.access_inbound {
+                mode |= windows_sys::PIPE_ACCESS_INBOUND;
+            }
+            if self.access_outbound {
+                mode |= windows_sys::PIPE_ACCESS_OUTBOUND;
+            }
+            if self.first_pipe_instance {
+                mode |= windows_sys::FILE_FLAG_FIRST_PIPE_INSTANCE;
+            }
+            if self.write_dac {
+                mode |= windows_sys::WRITE_DAC;
+            }
+            if self.write_owner {
+                mode |= windows_sys::WRITE_OWNER;
+            }
+            if self.access_system_security {
+                mode |= windows_sys::ACCESS_SYSTEM_SECURITY;
+            }
+            mode
+        };
+
         let h = windows_sys::CreateNamedPipeW(
             addr.as_ptr(),
-            self.open_mode,
-            self.pipe_mode,
+            open_mode,
+            pipe_mode,
             self.max_instances,
             self.out_buffer_size,
             self.in_buffer_size,
@@ -2339,8 +2373,10 @@ impl ServerOptions {
 /// See [`ClientOptions::open`].
 #[derive(Debug, Clone)]
 pub struct ClientOptions {
-    desired_access: u32,
+    generic_read: bool,
+    generic_write: bool,
     security_qos_flags: u32,
+    pipe_mode: PipeMode,
 }
 
 impl ClientOptions {
@@ -2359,9 +2395,11 @@ impl ClientOptions {
     /// ```
     pub fn new() -> Self {
         Self {
-            desired_access: windows_sys::GENERIC_READ | windows_sys::GENERIC_WRITE,
+            generic_read: true,
+            generic_write: true,
             security_qos_flags: windows_sys::SECURITY_IDENTIFICATION
                 | windows_sys::SECURITY_SQOS_PRESENT,
+            pipe_mode: PipeMode::Byte,
         }
     }
 
@@ -2372,7 +2410,7 @@ impl ClientOptions {
     /// [`GENERIC_READ`]: https://docs.microsoft.com/en-us/windows/win32/secauthz/generic-access-rights
     /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilew
     pub fn read(&mut self, allowed: bool) -> &mut Self {
-        bool_flag!(self.desired_access, allowed, windows_sys::GENERIC_READ);
+        self.generic_read = allowed;
         self
     }
 
@@ -2383,7 +2421,7 @@ impl ClientOptions {
     /// [`GENERIC_WRITE`]: https://docs.microsoft.com/en-us/windows/win32/secauthz/generic-access-rights
     /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilew
     pub fn write(&mut self, allowed: bool) -> &mut Self {
-        bool_flag!(self.desired_access, allowed, windows_sys::GENERIC_WRITE);
+        self.generic_write = allowed;
         self
     }
 
@@ -2414,6 +2452,15 @@ impl ClientOptions {
         self
     }
 
+    /// The pipe mode.
+    ///
+    /// The default pipe mode is [`PipeMode::Byte`]. See [`PipeMode`] for
+    /// documentation of what each mode means.
+    pub fn pipe_mode(&mut self, pipe_mode: PipeMode) -> &mut Self {
+        self.pipe_mode = pipe_mode;
+        self
+    }
+
     /// Opens the named pipe identified by `addr`.
     ///
     /// This opens the client using [`CreateFile`] with the
@@ -2492,13 +2539,24 @@ impl ClientOptions {
     ) -> io::Result<NamedPipeClient> {
         let addr = encode_addr(addr);
 
+        let desired_access = {
+            let mut access = 0;
+            if self.generic_read {
+                access |= windows_sys::GENERIC_READ;
+            }
+            if self.generic_write {
+                access |= windows_sys::GENERIC_WRITE;
+            }
+            access
+        };
+
         // NB: We could use a platform specialized `OpenOptions` here, but since
         // we have access to windows_sys it ultimately doesn't hurt to use
         // `CreateFile` explicitly since it allows the use of our already
         // well-structured wide `addr` to pass into CreateFileW.
         let h = windows_sys::CreateFileW(
             addr.as_ptr(),
-            self.desired_access,
+            desired_access,
             0,
             attrs as *mut _,
             windows_sys::OPEN_EXISTING,
@@ -2510,6 +2568,16 @@ impl ClientOptions {
             return Err(io::Error::last_os_error());
         }
 
+        if matches!(self.pipe_mode, PipeMode::Message) {
+            let mode = windows_sys::PIPE_READMODE_MESSAGE;
+            let result =
+                windows_sys::SetNamedPipeHandleState(h, &mode, ptr::null_mut(), ptr::null_mut());
+
+            if result == 0 {
+                return Err(io::Error::last_os_error());
+            }
+        }
+
         NamedPipeClient::from_raw_handle(h as _)
     }
 
diff --git a/tokio/src/process/mod.rs b/tokio/src/process/mod.rs
index 66e42127717..feada06f6d3 100644
--- a/tokio/src/process/mod.rs
+++ b/tokio/src/process/mod.rs
@@ -309,7 +309,8 @@ impl Command {
     ///
     /// ```no_run
     /// use tokio::process::Command;
-    /// let command = Command::new("sh");
+    /// let mut command = Command::new("sh");
+    /// # let _ = command.output(); // assert borrow checker
     /// ```
     ///
     /// [rust-lang/rust#37519]: https://github.com/rust-lang/rust/issues/37519
@@ -328,16 +329,20 @@ impl Command {
     /// Only one argument can be passed per use. So instead of:
     ///
     /// ```no_run
-    /// tokio::process::Command::new("sh")
-    ///   .arg("-C /path/to/repo");
+    /// let mut command = tokio::process::Command::new("sh");
+    /// command.arg("-C /path/to/repo");
+    ///
+    /// # let _ = command.output(); // assert borrow checker
     /// ```
     ///
     /// usage would be:
     ///
     /// ```no_run
-    /// tokio::process::Command::new("sh")
-    ///   .arg("-C")
-    ///   .arg("/path/to/repo");
+    /// let mut command = tokio::process::Command::new("sh");
+    /// command.arg("-C");
+    /// command.arg("/path/to/repo");
+    ///
+    /// # let _ = command.output(); // assert borrow checker
     /// ```
     ///
     /// To pass multiple arguments see [`args`].
@@ -349,11 +354,15 @@ impl Command {
     /// Basic usage:
     ///
     /// ```no_run
+    /// # async fn test() { // allow using await
     /// use tokio::process::Command;
     ///
-    /// let command = Command::new("ls")
+    /// let output = Command::new("ls")
     ///         .arg("-l")
-    ///         .arg("-a");
+    ///         .arg("-a")
+    ///         .output().await.unwrap();
+    /// # }
+    ///
     /// ```
     pub fn arg<S: AsRef<OsStr>>(&mut self, arg: S) -> &mut Command {
         self.std.arg(arg);
@@ -371,10 +380,13 @@ impl Command {
     /// Basic usage:
     ///
     /// ```no_run
+    /// # async fn test() { // allow using await
     /// use tokio::process::Command;
     ///
-    /// let command = Command::new("ls")
-    ///         .args(&["-l", "-a"]);
+    /// let output = Command::new("ls")
+    ///         .args(&["-l", "-a"])
+    ///         .output().await.unwrap();
+    /// # }
     /// ```
     pub fn args<I, S>(&mut self, args: I) -> &mut Command
     where
@@ -395,10 +407,13 @@ impl Command {
     /// Basic usage:
     ///
     /// ```no_run
+    /// # async fn test() { // allow using await
     /// use tokio::process::Command;
     ///
-    /// let command = Command::new("ls")
-    ///         .env("PATH", "/bin");
+    /// let output = Command::new("ls")
+    ///         .env("PATH", "/bin")
+    ///         .output().await.unwrap();
+    /// # }
     /// ```
     pub fn env<K, V>(&mut self, key: K, val: V) -> &mut Command
     where
@@ -416,6 +431,7 @@ impl Command {
     /// Basic usage:
     ///
     /// ```no_run
+    /// # async fn test() { // allow using await
     /// use tokio::process::Command;
     /// use std::process::{Stdio};
     /// use std::env;
@@ -426,11 +442,13 @@ impl Command {
     ///         k == "TERM" || k == "TZ" || k == "LANG" || k == "PATH"
     ///     ).collect();
     ///
-    /// let command = Command::new("printenv")
+    /// let output = Command::new("printenv")
     ///         .stdin(Stdio::null())
     ///         .stdout(Stdio::inherit())
     ///         .env_clear()
-    ///         .envs(&filtered_env);
+    ///         .envs(&filtered_env)
+    ///         .output().await.unwrap();
+    /// # }
     /// ```
     pub fn envs<I, K, V>(&mut self, vars: I) -> &mut Command
     where
@@ -449,10 +467,13 @@ impl Command {
     /// Basic usage:
     ///
     /// ```no_run
+    /// # async fn test() { // allow using await
     /// use tokio::process::Command;
     ///
-    /// let command = Command::new("ls")
-    ///         .env_remove("PATH");
+    /// let output = Command::new("ls")
+    ///         .env_remove("PATH")
+    ///         .output().await.unwrap();
+    /// # }
     /// ```
     pub fn env_remove<K: AsRef<OsStr>>(&mut self, key: K) -> &mut Command {
         self.std.env_remove(key);
@@ -466,10 +487,13 @@ impl Command {
     /// Basic usage:
     ///
     /// ```no_run
+    /// # async fn test() { // allow using await
     /// use tokio::process::Command;
     ///
-    /// let command = Command::new("ls")
-    ///         .env_clear();
+    /// let output = Command::new("ls")
+    ///         .env_clear()
+    ///         .output().await.unwrap();
+    /// # }
     /// ```
     pub fn env_clear(&mut self) -> &mut Command {
         self.std.env_clear();
@@ -493,10 +517,13 @@ impl Command {
     /// Basic usage:
     ///
     /// ```no_run
+    /// # async fn test() { // allow using await
     /// use tokio::process::Command;
     ///
-    /// let command = Command::new("ls")
-    ///         .current_dir("/bin");
+    /// let output = Command::new("ls")
+    ///         .current_dir("/bin")
+    ///         .output().await.unwrap();
+    /// # }
     /// ```
     pub fn current_dir<P: AsRef<Path>>(&mut self, dir: P) -> &mut Command {
         self.std.current_dir(dir);
@@ -516,11 +543,14 @@ impl Command {
     /// Basic usage:
     ///
     /// ```no_run
+    /// # async fn test() { // allow using await
     /// use std::process::{Stdio};
     /// use tokio::process::Command;
     ///
-    /// let command = Command::new("ls")
-    ///         .stdin(Stdio::null());
+    /// let output = Command::new("ls")
+    ///         .stdin(Stdio::null())
+    ///         .output().await.unwrap();
+    /// # }
     /// ```
     pub fn stdin<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command {
         self.std.stdin(cfg);
@@ -540,11 +570,14 @@ impl Command {
     /// Basic usage:
     ///
     /// ```no_run
+    /// # async fn test() { // allow using await
     /// use tokio::process::Command;
     /// use std::process::Stdio;
     ///
-    /// let command = Command::new("ls")
-    ///         .stdout(Stdio::null());
+    /// let output = Command::new("ls")
+    ///         .stdout(Stdio::null())
+    ///         .output().await.unwrap();
+    /// # }
     /// ```
     pub fn stdout<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command {
         self.std.stdout(cfg);
@@ -564,11 +597,14 @@ impl Command {
     /// Basic usage:
     ///
     /// ```no_run
+    /// # async fn test() { // allow using await
     /// use tokio::process::Command;
     /// use std::process::{Stdio};
     ///
-    /// let command = Command::new("ls")
-    ///         .stderr(Stdio::null());
+    /// let output = Command::new("ls")
+    ///         .stderr(Stdio::null())
+    ///         .output().await.unwrap();
+    /// # }
     /// ```
     pub fn stderr<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command {
         self.std.stderr(cfg);
@@ -707,10 +743,13 @@ impl Command {
     /// [`tokio::process::Command`]: crate::process::Command
     ///
     /// ```no_run
+    /// # async fn test() { // allow using await
     /// use tokio::process::Command;
     ///
-    /// let command = Command::new("ls")
-    ///         .process_group(0);
+    /// let output = Command::new("ls")
+    ///         .process_group(0)
+    ///         .output().await.unwrap();
+    /// # }
     /// ```
     #[cfg(unix)]
     #[cfg(tokio_unstable)]
diff --git a/tokio/src/process/unix/mod.rs b/tokio/src/process/unix/mod.rs
index 0345083dc09..78c792cc765 100644
--- a/tokio/src/process/unix/mod.rs
+++ b/tokio/src/process/unix/mod.rs
@@ -156,7 +156,7 @@ impl Future for Child {
 
 #[derive(Debug)]
 pub(crate) struct Pipe {
-    // Actually a pipe and not a File. However, we are reusing `File` to get
+    // Actually a pipe is not a File. However, we are reusing `File` to get
     // close on drop. This is a similar trick as `mio`.
     fd: File,
 }
diff --git a/tokio/src/process/unix/orphan.rs b/tokio/src/process/unix/orphan.rs
index 66572ef7c41..340719603be 100644
--- a/tokio/src/process/unix/orphan.rs
+++ b/tokio/src/process/unix/orphan.rs
@@ -294,7 +294,7 @@ pub(crate) mod test {
     #[cfg_attr(miri, ignore)] // Miri does not support epoll.
     #[test]
     fn does_not_register_signal_if_queue_empty() {
-        let (io_driver, io_handle) = IoDriver::new().unwrap();
+        let (io_driver, io_handle) = IoDriver::new(1024).unwrap();
         let signal_driver = SignalDriver::new(io_driver, &io_handle).unwrap();
         let handle = signal_driver.handle();
 
diff --git a/tokio/src/runtime/blocking/mod.rs b/tokio/src/runtime/blocking/mod.rs
index 88bdcfd6421..c42924be77d 100644
--- a/tokio/src/runtime/blocking/mod.rs
+++ b/tokio/src/runtime/blocking/mod.rs
@@ -17,8 +17,6 @@ cfg_trace! {
 mod schedule;
 mod shutdown;
 mod task;
-#[cfg(all(test, not(tokio_wasm)))]
-pub(crate) use schedule::NoopSchedule;
 pub(crate) use task::BlockingTask;
 
 use crate::runtime::Builder;
diff --git a/tokio/src/runtime/blocking/pool.rs b/tokio/src/runtime/blocking/pool.rs
index 9c536141996..e9f6b66e0fc 100644
--- a/tokio/src/runtime/blocking/pool.rs
+++ b/tokio/src/runtime/blocking/pool.rs
@@ -2,7 +2,7 @@
 
 use crate::loom::sync::{Arc, Condvar, Mutex};
 use crate::loom::thread;
-use crate::runtime::blocking::schedule::NoopSchedule;
+use crate::runtime::blocking::schedule::BlockingSchedule;
 use crate::runtime::blocking::{shutdown, BlockingTask};
 use crate::runtime::builder::ThreadNameFn;
 use crate::runtime::task::{self, JoinHandle};
@@ -120,7 +120,7 @@ struct Shared {
 }
 
 pub(crate) struct Task {
-    task: task::UnownedTask<NoopSchedule>,
+    task: task::UnownedTask<BlockingSchedule>,
     mandatory: Mandatory,
 }
 
@@ -151,7 +151,7 @@ impl From<SpawnError> for io::Error {
 }
 
 impl Task {
-    pub(crate) fn new(task: task::UnownedTask<NoopSchedule>, mandatory: Mandatory) -> Task {
+    pub(crate) fn new(task: task::UnownedTask<BlockingSchedule>, mandatory: Mandatory) -> Task {
         Task { task, mandatory }
     }
 
@@ -379,7 +379,8 @@ impl Spawner {
         #[cfg(not(all(tokio_unstable, feature = "tracing")))]
         let _ = name;
 
-        let (task, handle) = task::unowned(fut, NoopSchedule, id);
+        let (task, handle) = task::unowned(fut, BlockingSchedule::new(rt), id);
+
         let spawned = self.spawn_task(Task::new(task, is_mandatory), rt);
         (handle, spawned)
     }
diff --git a/tokio/src/runtime/blocking/schedule.rs b/tokio/src/runtime/blocking/schedule.rs
index 54252241d94..edf775be8be 100644
--- a/tokio/src/runtime/blocking/schedule.rs
+++ b/tokio/src/runtime/blocking/schedule.rs
@@ -1,15 +1,52 @@
+#[cfg(feature = "test-util")]
+use crate::runtime::scheduler;
 use crate::runtime::task::{self, Task};
+use crate::runtime::Handle;
 
-/// `task::Schedule` implementation that does nothing. This is unique to the
-/// blocking scheduler as tasks scheduled are not really futures but blocking
-/// operations.
+/// `task::Schedule` implementation that does nothing (except some bookkeeping
+/// in test-util builds). This is unique to the blocking scheduler as tasks
+/// scheduled are not really futures but blocking operations.
 ///
 /// We avoid storing the task by forgetting it in `bind` and re-materializing it
-/// in `release.
-pub(crate) struct NoopSchedule;
+/// in `release`.
+pub(crate) struct BlockingSchedule {
+    #[cfg(feature = "test-util")]
+    handle: Handle,
+}
+
+impl BlockingSchedule {
+    #[cfg_attr(not(feature = "test-util"), allow(unused_variables))]
+    pub(crate) fn new(handle: &Handle) -> Self {
+        #[cfg(feature = "test-util")]
+        {
+            match &handle.inner {
+                scheduler::Handle::CurrentThread(handle) => {
+                    handle.driver.clock.inhibit_auto_advance();
+                }
+                #[cfg(all(feature = "rt-multi-thread", not(tokio_wasi)))]
+                scheduler::Handle::MultiThread(_) => {}
+            }
+        }
+        BlockingSchedule {
+            #[cfg(feature = "test-util")]
+            handle: handle.clone(),
+        }
+    }
+}
 
-impl task::Schedule for NoopSchedule {
+impl task::Schedule for BlockingSchedule {
     fn release(&self, _task: &Task<Self>) -> Option<Task<Self>> {
+        #[cfg(feature = "test-util")]
+        {
+            match &self.handle.inner {
+                scheduler::Handle::CurrentThread(handle) => {
+                    handle.driver.clock.allow_auto_advance();
+                    handle.driver.unpark();
+                }
+                #[cfg(all(feature = "rt-multi-thread", not(tokio_wasi)))]
+                scheduler::Handle::MultiThread(_) => {}
+            }
+        }
         None
     }
 
diff --git a/tokio/src/runtime/builder.rs b/tokio/src/runtime/builder.rs
index d49a4da39ae..ea0df2e3b4c 100644
--- a/tokio/src/runtime/builder.rs
+++ b/tokio/src/runtime/builder.rs
@@ -44,6 +44,7 @@ pub struct Builder {
 
     /// Whether or not to enable the I/O driver
     enable_io: bool,
+    nevents: usize,
 
     /// Whether or not to enable the time driver
     enable_time: bool,
@@ -181,6 +182,7 @@ cfg_unstable! {
 
 pub(crate) type ThreadNameFn = std::sync::Arc<dyn Fn() -> String + Send + Sync + 'static>;
 
+#[derive(Clone, Copy)]
 pub(crate) enum Kind {
     CurrentThread,
     #[cfg(all(feature = "rt-multi-thread", not(tokio_wasi)))]
@@ -228,6 +230,7 @@ impl Builder {
 
             // I/O defaults to "off"
             enable_io: false,
+            nevents: 1024,
 
             // Time defaults to "off"
             enable_time: false,
@@ -235,6 +238,7 @@ impl Builder {
             // The clock starts not-paused
             start_paused: false,
 
+            // Read from environment variable first in multi-threaded mode.
             // Default to lazy auto-detection (one thread per CPU core)
             worker_threads: None,
 
@@ -302,6 +306,8 @@ impl Builder {
     /// This can be any number above 0 though it is advised to keep this value
     /// on the smaller side.
     ///
+    /// This will override the value read from environment variable `TOKIO_WORKER_THREADS`.
+    ///
     /// # Default
     ///
     /// The default value is the number of cores available to the system.
@@ -647,6 +653,7 @@ impl Builder {
             enable_io: self.enable_io,
             enable_time: self.enable_time,
             start_paused: self.start_paused,
+            nevents: self.nevents,
         }
     }
 
@@ -938,6 +945,25 @@ cfg_io_driver! {
             self.enable_io = true;
             self
         }
+
+        /// Enables the I/O driver and configures the max number of events to be
+        /// processed per tick.
+        ///
+        /// # Examples
+        ///
+        /// ```
+        /// use tokio::runtime;
+        ///
+        /// let rt = runtime::Builder::new_current_thread()
+        ///     .enable_io()
+        ///     .max_io_events_per_tick(1024)
+        ///     .build()
+        ///     .unwrap();
+        /// ```
+        pub fn max_io_events_per_tick(&mut self, capacity: usize) -> &mut Self {
+            self.nevents = capacity;
+            self
+        }
     }
 }
 
diff --git a/tokio/src/runtime/context.rs b/tokio/src/runtime/context.rs
index 2e54c8ba366..a2401306634 100644
--- a/tokio/src/runtime/context.rs
+++ b/tokio/src/runtime/context.rs
@@ -15,6 +15,10 @@ cfg_rt! {
 }
 
 struct Context {
+    /// Uniquely identifies the current thread
+    #[cfg(feature = "rt")]
+    thread_id: Cell<Option<ThreadId>>,
+
     /// Handle to the runtime scheduler running on the current thread.
     #[cfg(feature = "rt")]
     handle: RefCell<Option<scheduler::Handle>>,
@@ -46,6 +50,9 @@ struct Context {
 tokio_thread_local! {
     static CONTEXT: Context = {
         Context {
+            #[cfg(feature = "rt")]
+            thread_id: Cell::new(None),
+
             /// Tracks the current runtime handle to use when spawning,
             /// accessing drivers, etc...
             #[cfg(feature = "rt")]
@@ -72,7 +79,7 @@ tokio_thread_local! {
     }
 }
 
-#[cfg(feature = "macros")]
+#[cfg(any(feature = "macros", all(feature = "sync", feature = "rt")))]
 pub(crate) fn thread_rng_n(n: u32) -> u32 {
     CONTEXT.with(|ctx| ctx.rng.fastrand_n(n))
 }
@@ -82,10 +89,23 @@ pub(super) fn budget<R>(f: impl FnOnce(&Cell<coop::Budget>) -> R) -> Result<R, A
 }
 
 cfg_rt! {
-    use crate::runtime::TryCurrentError;
+    use crate::runtime::{ThreadId, TryCurrentError};
 
     use std::fmt;
 
+    pub(crate) fn thread_id() -> Result<ThreadId, AccessError> {
+        CONTEXT.try_with(|ctx| {
+            match ctx.thread_id.get() {
+                Some(id) => id,
+                None => {
+                    let id = ThreadId::next();
+                    ctx.thread_id.set(Some(id));
+                    id
+                }
+            }
+        })
+    }
+
     #[derive(Debug, Clone, Copy)]
     #[must_use]
     pub(crate) enum EnterRuntime {
diff --git a/tokio/src/runtime/driver.rs b/tokio/src/runtime/driver.rs
index 8f9c5122b85..572fdefb0da 100644
--- a/tokio/src/runtime/driver.rs
+++ b/tokio/src/runtime/driver.rs
@@ -36,16 +36,16 @@ pub(crate) struct Cfg {
     pub(crate) enable_time: bool,
     pub(crate) enable_pause_time: bool,
     pub(crate) start_paused: bool,
+    pub(crate) nevents: usize,
 }
 
 impl Driver {
     pub(crate) fn new(cfg: Cfg) -> io::Result<(Self, Handle)> {
-        let (io_stack, io_handle, signal_handle) = create_io_stack(cfg.enable_io)?;
+        let (io_stack, io_handle, signal_handle) = create_io_stack(cfg.enable_io, cfg.nevents)?;
 
         let clock = create_clock(cfg.enable_pause_time, cfg.start_paused);
 
-        let (time_driver, time_handle) =
-            create_time_driver(cfg.enable_time, io_stack, clock.clone());
+        let (time_driver, time_handle) = create_time_driver(cfg.enable_time, io_stack, &clock);
 
         Ok((
             Self { inner: time_driver },
@@ -110,10 +110,8 @@ impl Handle {
                 .expect("A Tokio 1.x context was found, but timers are disabled. Call `enable_time` on the runtime builder to enable timers.")
         }
 
-        cfg_test_util! {
-            pub(crate) fn clock(&self) -> &Clock {
-                &self.clock
-            }
+        pub(crate) fn clock(&self) -> &Clock {
+            &self.clock
         }
     }
 }
@@ -135,12 +133,12 @@ cfg_io_driver! {
         Disabled(UnparkThread),
     }
 
-    fn create_io_stack(enabled: bool) -> io::Result<(IoStack, IoHandle, SignalHandle)> {
+    fn create_io_stack(enabled: bool, nevents: usize) -> io::Result<(IoStack, IoHandle, SignalHandle)> {
         #[cfg(loom)]
         assert!(!enabled);
 
         let ret = if enabled {
-            let (io_driver, io_handle) = crate::runtime::io::Driver::new()?;
+            let (io_driver, io_handle) = crate::runtime::io::Driver::new(nevents)?;
 
             let (signal_driver, signal_handle) = create_signal_driver(io_driver, &io_handle)?;
             let process_driver = create_process_driver(signal_driver);
@@ -201,7 +199,7 @@ cfg_not_io_driver! {
     #[derive(Debug)]
     pub(crate) struct IoStack(ParkThread);
 
-    fn create_io_stack(_enabled: bool) -> io::Result<(IoStack, IoHandle, SignalHandle)> {
+    fn create_io_stack(_enabled: bool, _nevents: usize) -> io::Result<(IoStack, IoHandle, SignalHandle)> {
         let park_thread = ParkThread::new();
         let unpark_thread = park_thread.unpark();
         Ok((IoStack(park_thread), unpark_thread, Default::default()))
@@ -288,7 +286,7 @@ cfg_time! {
     fn create_time_driver(
         enable: bool,
         io_stack: IoStack,
-        clock: Clock,
+        clock: &Clock,
     ) -> (TimeDriver, TimeHandle) {
         if enable {
             let (driver, handle) = crate::runtime::time::Driver::new(io_stack, clock);
@@ -336,7 +334,7 @@ cfg_not_time! {
     fn create_time_driver(
         _enable: bool,
         io_stack: IoStack,
-        _clock: Clock,
+        _clock: &Clock,
     ) -> (TimeDriver, TimeHandle) {
         (io_stack, ())
     }
diff --git a/tokio/src/runtime/handle.rs b/tokio/src/runtime/handle.rs
index da47ecb27b2..fca1cbb4e32 100644
--- a/tokio/src/runtime/handle.rs
+++ b/tokio/src/runtime/handle.rs
@@ -118,9 +118,9 @@ impl Handle {
     /// thread pool. The thread pool is then responsible for polling the future
     /// until it completes.
     ///
-    /// You do not have to `.await` the returned `JoinHandle` to make the
-    /// provided future start execution. It will start running in the background
-    /// immediately when `spawn` is called.
+    /// The provided future will start running in the background immediately
+    /// when `spawn` is called, even if you don't await the returned
+    /// `JoinHandle`.
     ///
     /// See [module level][mod] documentation for more details.
     ///
@@ -152,7 +152,7 @@ impl Handle {
         self.spawn_named(future, None)
     }
 
-    /// Runs the provided function on an executor dedicated to blocking.
+    /// Runs the provided function on an executor dedicated to blocking
     /// operations.
     ///
     /// # Examples
diff --git a/tokio/src/runtime/io/mod.rs b/tokio/src/runtime/io/mod.rs
index 02039f2a49c..2e578b6ee6b 100644
--- a/tokio/src/runtime/io/mod.rs
+++ b/tokio/src/runtime/io/mod.rs
@@ -60,6 +60,7 @@ pub(crate) struct Handle {
 pub(crate) struct ReadyEvent {
     tick: u8,
     pub(crate) ready: Ready,
+    is_shutdown: bool,
 }
 
 struct IoDispatcher {
@@ -104,7 +105,7 @@ fn _assert_kinds() {
 impl Driver {
     /// Creates a new event loop, returning any error that happened during the
     /// creation.
-    pub(crate) fn new() -> io::Result<(Driver, Handle)> {
+    pub(crate) fn new(nevents: usize) -> io::Result<(Driver, Handle)> {
         let poll = mio::Poll::new()?;
         #[cfg(not(tokio_wasi))]
         let waker = mio::Waker::new(poll.registry(), TOKEN_WAKEUP)?;
@@ -116,7 +117,7 @@ impl Driver {
         let driver = Driver {
             tick: 0,
             signal_ready: false,
-            events: mio::Events::with_capacity(1024),
+            events: mio::Events::with_capacity(nevents),
             poll,
             resources: slab,
         };
@@ -147,9 +148,8 @@ impl Driver {
 
         if handle.shutdown() {
             self.resources.for_each(|io| {
-                // If a task is waiting on the I/O resource, notify it. The task
-                // will then attempt to use the I/O resource and fail due to the
-                // driver being shutdown. And shutdown will clear all wakers.
+                // If a task is waiting on the I/O resource, notify it that the
+                // runtime is being shutdown. And shutdown will clear all wakers.
                 io.shutdown();
             });
         }
@@ -282,16 +282,12 @@ impl Handle {
         true
     }
 
-    fn is_shutdown(&self) -> bool {
-        return self.io_dispatch.read().unwrap().is_shutdown;
-    }
-
     fn allocate(&self) -> io::Result<(slab::Address, slab::Ref<ScheduledIo>)> {
         let io = self.io_dispatch.read().unwrap();
         if io.is_shutdown {
             return Err(io::Error::new(
                 io::ErrorKind::Other,
-                "failed to find event loop",
+                crate::util::error::RUNTIME_SHUTTING_DOWN_ERROR,
             ));
         }
         io.allocator.allocate().ok_or_else(|| {
diff --git a/tokio/src/runtime/io/registration.rs b/tokio/src/runtime/io/registration.rs
index 7b95f7f0409..140b9240ae4 100644
--- a/tokio/src/runtime/io/registration.rs
+++ b/tokio/src/runtime/io/registration.rs
@@ -148,7 +148,7 @@ impl Registration {
         let coop = ready!(crate::runtime::coop::poll_proceed(cx));
         let ev = ready!(self.shared.poll_readiness(cx, direction));
 
-        if self.handle().is_shutdown() {
+        if ev.is_shutdown {
             return Poll::Ready(Err(gone()));
         }
 
@@ -217,28 +217,22 @@ impl Drop for Registration {
 }
 
 fn gone() -> io::Error {
-    io::Error::new(io::ErrorKind::Other, "IO driver has terminated")
+    io::Error::new(
+        io::ErrorKind::Other,
+        crate::util::error::RUNTIME_SHUTTING_DOWN_ERROR,
+    )
 }
 
 cfg_io_readiness! {
     impl Registration {
         pub(crate) async fn readiness(&self, interest: Interest) -> io::Result<ReadyEvent> {
-            use std::future::Future;
-            use std::pin::Pin;
+            let ev = self.shared.readiness(interest).await;
 
-            let fut = self.shared.readiness(interest);
-            pin!(fut);
-
-            crate::future::poll_fn(|cx| {
-                if self.handle().is_shutdown() {
-                    return Poll::Ready(Err(io::Error::new(
-                        io::ErrorKind::Other,
-                        crate::util::error::RUNTIME_SHUTTING_DOWN_ERROR
-                    )));
-                }
+            if ev.is_shutdown {
+                return Err(gone())
+            }
 
-                Pin::new(&mut fut).poll(cx).map(Ok)
-            }).await
+            Ok(ev)
         }
 
         pub(crate) async fn async_io<R>(&self, interest: Interest, mut f: impl FnMut() -> io::Result<R>) -> io::Result<R> {
diff --git a/tokio/src/runtime/io/scheduled_io.rs b/tokio/src/runtime/io/scheduled_io.rs
index af42ba8a31e..197a4e0e211 100644
--- a/tokio/src/runtime/io/scheduled_io.rs
+++ b/tokio/src/runtime/io/scheduled_io.rs
@@ -46,9 +46,6 @@ struct Waiters {
 
     /// Waker used for AsyncWrite.
     writer: Option<Waker>,
-
-    /// True if this ScheduledIo has been killed due to IO driver shutdown.
-    is_shutdown: bool,
 }
 
 cfg_io_readiness! {
@@ -95,7 +92,7 @@ cfg_io_readiness! {
 
 // The `ScheduledIo::readiness` (`AtomicUsize`) is packed full of goodness.
 //
-// | reserved | generation |  driver tick | readiness |
+// | shutdown | generation |  driver tick | readiness |
 // |----------+------------+--------------+-----------|
 // |   1 bit  |   7 bits   +    8 bits    +   16 bits |
 
@@ -105,6 +102,8 @@ const TICK: bit::Pack = READINESS.then(8);
 
 const GENERATION: bit::Pack = TICK.then(7);
 
+const SHUTDOWN: bit::Pack = GENERATION.then(1);
+
 #[test]
 fn test_generations_assert_same() {
     assert_eq!(super::GENERATION, GENERATION);
@@ -138,9 +137,11 @@ impl ScheduledIo {
     }
 
     /// Invoked when the IO driver is shut down; forces this ScheduledIo into a
-    /// permanently ready state.
+    /// permanently shutdown state.
     pub(super) fn shutdown(&self) {
-        self.wake0(Ready::ALL, true)
+        let mask = SHUTDOWN.pack(1, 0);
+        self.readiness.fetch_or(mask, AcqRel);
+        self.wake(Ready::ALL);
     }
 
     /// Sets the readiness on this `ScheduledIo` by invoking the given closure on
@@ -219,16 +220,10 @@ impl ScheduledIo {
     /// than 32 wakers to notify, if the stack array fills up, the lock is
     /// released, the array is cleared, and the iteration continues.
     pub(super) fn wake(&self, ready: Ready) {
-        self.wake0(ready, false);
-    }
-
-    fn wake0(&self, ready: Ready, shutdown: bool) {
         let mut wakers = WakeList::new();
 
         let mut waiters = self.waiters.lock();
 
-        waiters.is_shutdown |= shutdown;
-
         // check for AsyncRead slot
         if ready.is_readable() {
             if let Some(waker) = waiters.reader.take() {
@@ -283,6 +278,7 @@ impl ScheduledIo {
         ReadyEvent {
             tick: TICK.unpack(curr) as u8,
             ready: interest.mask() & Ready::from_usize(READINESS.unpack(curr)),
+            is_shutdown: SHUTDOWN.unpack(curr) != 0,
         }
     }
 
@@ -299,8 +295,9 @@ impl ScheduledIo {
         let curr = self.readiness.load(Acquire);
 
         let ready = direction.mask() & Ready::from_usize(READINESS.unpack(curr));
+        let is_shutdown = SHUTDOWN.unpack(curr) != 0;
 
-        if ready.is_empty() {
+        if ready.is_empty() && !is_shutdown {
             // Update the task info
             let mut waiters = self.waiters.lock();
             let slot = match direction {
@@ -325,10 +322,12 @@ impl ScheduledIo {
             // taking the waiters lock
             let curr = self.readiness.load(Acquire);
             let ready = direction.mask() & Ready::from_usize(READINESS.unpack(curr));
-            if waiters.is_shutdown {
+            let is_shutdown = SHUTDOWN.unpack(curr) != 0;
+            if is_shutdown {
                 Poll::Ready(ReadyEvent {
                     tick: TICK.unpack(curr) as u8,
                     ready: direction.mask(),
+                    is_shutdown,
                 })
             } else if ready.is_empty() {
                 Poll::Pending
@@ -336,12 +335,14 @@ impl ScheduledIo {
                 Poll::Ready(ReadyEvent {
                     tick: TICK.unpack(curr) as u8,
                     ready,
+                    is_shutdown,
                 })
             }
         } else {
             Poll::Ready(ReadyEvent {
                 tick: TICK.unpack(curr) as u8,
                 ready,
+                is_shutdown,
             })
         }
     }
@@ -433,16 +434,17 @@ cfg_io_readiness! {
                         // Optimistically check existing readiness
                         let curr = scheduled_io.readiness.load(SeqCst);
                         let ready = Ready::from_usize(READINESS.unpack(curr));
+                        let is_shutdown = SHUTDOWN.unpack(curr) != 0;
 
                         // Safety: `waiter.interest` never changes
                         let interest = unsafe { (*waiter.get()).interest };
                         let ready = ready.intersection(interest);
 
-                        if !ready.is_empty() {
+                        if !ready.is_empty() || is_shutdown {
                             // Currently ready!
                             let tick = TICK.unpack(curr) as u8;
                             *state = State::Done;
-                            return Poll::Ready(ReadyEvent { tick, ready });
+                            return Poll::Ready(ReadyEvent { tick, ready, is_shutdown });
                         }
 
                         // Wasn't ready, take the lock (and check again while locked).
@@ -450,18 +452,19 @@ cfg_io_readiness! {
 
                         let curr = scheduled_io.readiness.load(SeqCst);
                         let mut ready = Ready::from_usize(READINESS.unpack(curr));
+                        let is_shutdown = SHUTDOWN.unpack(curr) != 0;
 
-                        if waiters.is_shutdown {
+                        if is_shutdown {
                             ready = Ready::ALL;
                         }
 
                         let ready = ready.intersection(interest);
 
-                        if !ready.is_empty() {
+                        if !ready.is_empty() || is_shutdown {
                             // Currently ready!
                             let tick = TICK.unpack(curr) as u8;
                             *state = State::Done;
-                            return Poll::Ready(ReadyEvent { tick, ready });
+                            return Poll::Ready(ReadyEvent { tick, ready, is_shutdown });
                         }
 
                         // Not ready even after locked, insert into list...
@@ -510,14 +513,26 @@ cfg_io_readiness! {
                         drop(waiters);
                     }
                     State::Done => {
-                        let tick = TICK.unpack(scheduled_io.readiness.load(Acquire)) as u8;
-
                         // Safety: State::Done means it is no longer shared
                         let w = unsafe { &mut *waiter.get() };
 
+                        let curr = scheduled_io.readiness.load(Acquire);
+                        let is_shutdown = SHUTDOWN.unpack(curr) != 0;
+
+                        // The returned tick might be newer than the event
+                        // which notified our waker. This is ok because the future
+                        // still didn't return `Poll::Ready`.
+                        let tick = TICK.unpack(curr) as u8;
+
+                        // The readiness state could have been cleared in the meantime,
+                        // but we allow the returned ready set to be empty.
+                        let curr_ready = Ready::from_usize(READINESS.unpack(curr));
+                        let ready = curr_ready.intersection(w.interest);
+
                         return Poll::Ready(ReadyEvent {
                             tick,
-                            ready: Ready::from_interest(w.interest),
+                            ready,
+                            is_shutdown,
                         });
                     }
                 }
diff --git a/tokio/src/runtime/metrics/batch.rs b/tokio/src/runtime/metrics/batch.rs
index f1c3fa6b747..4e6b28d68ed 100644
--- a/tokio/src/runtime/metrics/batch.rs
+++ b/tokio/src/runtime/metrics/batch.rs
@@ -11,9 +11,12 @@ pub(crate) struct MetricsBatch {
     /// Number of times the worker woke w/o doing work.
     noop_count: u64,
 
-    /// Number of times stolen.
+    /// Number of tasks stolen.
     steal_count: u64,
 
+    /// Number of times tasks where stolen.
+    steal_operations: u64,
+
     /// Number of tasks that were polled by the worker.
     poll_count: u64,
 
@@ -39,6 +42,7 @@ impl MetricsBatch {
             park_count: 0,
             noop_count: 0,
             steal_count: 0,
+            steal_operations: 0,
             poll_count: 0,
             poll_count_on_last_park: 0,
             local_schedule_count: 0,
@@ -52,6 +56,9 @@ impl MetricsBatch {
         worker.park_count.store(self.park_count, Relaxed);
         worker.noop_count.store(self.noop_count, Relaxed);
         worker.steal_count.store(self.steal_count, Relaxed);
+        worker
+            .steal_operations
+            .store(self.steal_operations, Relaxed);
         worker.poll_count.store(self.poll_count, Relaxed);
 
         worker
@@ -98,6 +105,10 @@ cfg_rt_multi_thread! {
             self.steal_count += by as u64;
         }
 
+        pub(crate) fn incr_steal_operations(&mut self) {
+            self.steal_operations += 1;
+        }
+
         pub(crate) fn incr_overflow_count(&mut self) {
             self.overflow_count += 1;
         }
diff --git a/tokio/src/runtime/metrics/mock.rs b/tokio/src/runtime/metrics/mock.rs
index 6b9cf704f42..c388dc06981 100644
--- a/tokio/src/runtime/metrics/mock.rs
+++ b/tokio/src/runtime/metrics/mock.rs
@@ -38,6 +38,7 @@ impl MetricsBatch {
 cfg_rt_multi_thread! {
     impl MetricsBatch {
         pub(crate) fn incr_steal_count(&mut self, _by: u16) {}
+        pub(crate) fn incr_steal_operations(&mut self) {}
         pub(crate) fn incr_overflow_count(&mut self) {}
     }
 }
diff --git a/tokio/src/runtime/metrics/runtime.rs b/tokio/src/runtime/metrics/runtime.rs
index dee14a45729..d29cb3d48ff 100644
--- a/tokio/src/runtime/metrics/runtime.rs
+++ b/tokio/src/runtime/metrics/runtime.rs
@@ -210,10 +210,57 @@ impl RuntimeMetrics {
             .load(Relaxed)
     }
 
+    /// Returns the number of tasks the given worker thread stole from
+    /// another worker thread.
+    ///
+    /// This metric only applies to the **multi-threaded** runtime and will
+    /// always return `0` when using the current thread runtime.
+    ///
+    /// The worker steal count starts at zero when the runtime is created and
+    /// increases by `N` each time the worker has processed its scheduled queue
+    /// and successfully steals `N` more pending tasks from another worker.
+    ///
+    /// The counter is monotonically increasing. It is never decremented or
+    /// reset to zero.
+    ///
+    /// # Arguments
+    ///
+    /// `worker` is the index of the worker being queried. The given value must
+    /// be between 0 and `num_workers()`. The index uniquely identifies a single
+    /// worker and will continue to identify the worker throughout the lifetime
+    /// of the runtime instance.
+    ///
+    /// # Panics
+    ///
+    /// The method panics when `worker` represents an invalid worker, i.e. is
+    /// greater than or equal to `num_workers()`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use tokio::runtime::Handle;
+    ///
+    /// #[tokio::main]
+    /// async fn main() {
+    ///     let metrics = Handle::current().metrics();
+    ///
+    ///     let n = metrics.worker_steal_count(0);
+    ///     println!("worker 0 has stolen {} tasks", n);
+    /// }
+    /// ```
+    pub fn worker_steal_count(&self, worker: usize) -> u64 {
+        self.handle
+            .inner
+            .worker_metrics(worker)
+            .steal_count
+            .load(Relaxed)
+    }
+
     /// Returns the number of times the given worker thread stole tasks from
     /// another worker thread.
     ///
-    /// This metric only applies to the **multi-threaded** runtime and will always return `0` when using the current thread runtime.
+    /// This metric only applies to the **multi-threaded** runtime and will
+    /// always return `0` when using the current thread runtime.
     ///
     /// The worker steal count starts at zero when the runtime is created and
     /// increases by one each time the worker has processed its scheduled queue
@@ -243,15 +290,15 @@ impl RuntimeMetrics {
     /// async fn main() {
     ///     let metrics = Handle::current().metrics();
     ///
-    ///     let n = metrics.worker_noop_count(0);
+    ///     let n = metrics.worker_steal_operations(0);
     ///     println!("worker 0 has stolen tasks {} times", n);
     /// }
     /// ```
-    pub fn worker_steal_count(&self, worker: usize) -> u64 {
+    pub fn worker_steal_operations(&self, worker: usize) -> u64 {
         self.handle
             .inner
             .worker_metrics(worker)
-            .steal_count
+            .steal_operations
             .load(Relaxed)
     }
 
@@ -328,8 +375,8 @@ impl RuntimeMetrics {
     /// async fn main() {
     ///     let metrics = Handle::current().metrics();
     ///
-    ///     let n = metrics.worker_poll_count(0);
-    ///     println!("worker 0 has polled {} tasks", n);
+    ///     let n = metrics.worker_total_busy_duration(0);
+    ///     println!("worker 0 was busy for a total of {:?}", n);
     /// }
     /// ```
     pub fn worker_total_busy_duration(&self, worker: usize) -> Duration {
diff --git a/tokio/src/runtime/metrics/worker.rs b/tokio/src/runtime/metrics/worker.rs
index ec58de6b3a0..a40c76effbf 100644
--- a/tokio/src/runtime/metrics/worker.rs
+++ b/tokio/src/runtime/metrics/worker.rs
@@ -17,9 +17,12 @@ pub(crate) struct WorkerMetrics {
     /// Number of times the worker woke then parked again without doing work.
     pub(crate) noop_count: AtomicU64,
 
-    /// Number of times the worker attempted to steal.
+    /// Number of tasks the worker stole.
     pub(crate) steal_count: AtomicU64,
 
+    /// Number of times the worker stole
+    pub(crate) steal_operations: AtomicU64,
+
     /// Number of tasks the worker polled.
     pub(crate) poll_count: AtomicU64,
 
@@ -43,6 +46,7 @@ impl WorkerMetrics {
             park_count: AtomicU64::new(0),
             noop_count: AtomicU64::new(0),
             steal_count: AtomicU64::new(0),
+            steal_operations: AtomicU64::new(0),
             poll_count: AtomicU64::new(0),
             overflow_count: AtomicU64::new(0),
             busy_duration_total: AtomicU64::new(0),
diff --git a/tokio/src/runtime/mod.rs b/tokio/src/runtime/mod.rs
index 45b79b0ac81..8cd99917546 100644
--- a/tokio/src/runtime/mod.rs
+++ b/tokio/src/runtime/mod.rs
@@ -156,9 +156,11 @@
 //! multi-thread scheduler spawns threads to schedule tasks and for `spawn_blocking`
 //! calls.
 //!
-//! While the `Runtime` is active, threads may shutdown after periods of being
-//! idle. Once `Runtime` is dropped, all runtime threads are forcibly shutdown.
-//! Any tasks that have not yet completed will be dropped.
+//! While the `Runtime` is active, threads may shut down after periods of being
+//! idle. Once `Runtime` is dropped, all runtime threads have usually been
+//! terminated, but in the presence of unstoppable spawned work are not
+//! guaranteed to have been terminated. See the
+//! [struct level documentation](Runtime#shutdown) for more details.
 //!
 //! [tasks]: crate::task
 //! [`Runtime`]: Runtime
@@ -237,6 +239,9 @@ cfg_rt! {
     mod runtime;
     pub use runtime::{Runtime, RuntimeFlavor};
 
+    mod thread_id;
+    pub(crate) use thread_id::ThreadId;
+
     cfg_metrics! {
         mod metrics;
         pub use metrics::RuntimeMetrics;
diff --git a/tokio/src/runtime/runtime.rs b/tokio/src/runtime/runtime.rs
index 3d4fd67884d..60c3fc77670 100644
--- a/tokio/src/runtime/runtime.rs
+++ b/tokio/src/runtime/runtime.rs
@@ -24,16 +24,29 @@ cfg_rt_multi_thread! {
 ///
 /// # Shutdown
 ///
-/// Shutting down the runtime is done by dropping the value. The current
-/// thread will block until the shut down operation has completed.
+/// Shutting down the runtime is done by dropping the value, or calling
+/// [`Runtime::shutdown_background`] or [`Runtime::shutdown_timeout`].
 ///
-/// * Drain any scheduled work queues.
-/// * Drop any futures that have not yet completed.
-/// * Drop the reactor.
+/// Tasks spawned through [`Runtime::spawn`] keep running until they yield.
+/// Then they are dropped. They are not *guaranteed* to run to completion, but
+/// *might* do so if they do not yield until completion.
 ///
-/// Once the reactor has dropped, any outstanding I/O resources bound to
-/// that reactor will no longer function. Calling any method on them will
-/// result in an error.
+/// Blocking functions spawned through [`Runtime::spawn_blocking`] keep running
+/// until they return.
+///
+/// The thread initiating the shutdown blocks until all spawned work has been
+/// stopped. This can take an indefinite amount of time. The `Drop`
+/// implementation waits forever for this.
+///
+/// `shutdown_background` and `shutdown_timeout` can be used if waiting forever
+/// is undesired. When the timeout is reached, spawned work that did not stop
+/// in time and threads running it are leaked. The work continues to run until
+/// one of the stopping conditions is fulfilled, but the thread initiating the
+/// shutdown is unblocked.
+///
+/// Once the runtime has been dropped, any outstanding I/O resources bound to
+/// it will no longer function. Calling any method on them will result in an
+/// error.
 ///
 /// # Sharing
 ///
@@ -138,6 +151,9 @@ impl Runtime {
     /// The returned handle can be used to spawn tasks that run on this runtime, and can
     /// be cloned to allow moving the `Handle` to other threads.
     ///
+    /// Calling [`Handle::block_on`] on a handle to a `current_thread` runtime is error-prone.
+    /// Refer to the documentation of [`Handle::block_on`] for more.
+    ///
     /// # Examples
     ///
     /// ```
@@ -160,9 +176,9 @@ impl Runtime {
     /// thread pool. The thread pool is then responsible for polling the future
     /// until it completes.
     ///
-    /// You do not have to `.await` the returned `JoinHandle` to make the
-    /// provided future start execution. It will start running in the
-    /// background immediately when `spawn` is called.
+    /// The provided future will start running in the background immediately
+    /// when `spawn` is called, even if you don't await the returned
+    /// `JoinHandle`.
     ///
     /// See [module level][mod] documentation for more details.
     ///
@@ -224,6 +240,13 @@ impl Runtime {
     /// complete, and yielding its resolved result. Any tasks or timers
     /// which the future spawns internally will be executed on the runtime.
     ///
+    /// # Non-worker future
+    ///
+    /// Note that the future required by this function does not run as a
+    /// worker. The expectation is that other tasks are spawned by the future here.
+    /// Awaiting on other futures from the future provided here will not
+    /// perform as fast as those spawned as workers.
+    ///
     /// # Multi thread scheduler
     ///
     /// When the multi thread scheduler is used this will allow futures
@@ -319,18 +342,9 @@ impl Runtime {
     }
 
     /// Shuts down the runtime, waiting for at most `duration` for all spawned
-    /// task to shutdown.
+    /// work to stop.
     ///
-    /// Usually, dropping a `Runtime` handle is sufficient as tasks are able to
-    /// shutdown in a timely fashion. However, dropping a `Runtime` will wait
-    /// indefinitely for all tasks to terminate, and there are cases where a long
-    /// blocking task has been spawned, which can block dropping `Runtime`.
-    ///
-    /// In this case, calling `shutdown_timeout` with an explicit wait timeout
-    /// can work. The `shutdown_timeout` will signal all tasks to shutdown and
-    /// will wait for at most `duration` for all spawned tasks to terminate. If
-    /// `timeout` elapses before all tasks are dropped, the function returns and
-    /// outstanding tasks are potentially leaked.
+    /// See the [struct level documentation](Runtime#shutdown) for more details.
     ///
     /// # Examples
     ///
@@ -359,7 +373,7 @@ impl Runtime {
         self.blocking_pool.shutdown(Some(duration));
     }
 
-    /// Shuts down the runtime, without waiting for any spawned tasks to shutdown.
+    /// Shuts down the runtime, without waiting for any spawned work to stop.
     ///
     /// This can be useful if you want to drop a runtime from within another runtime.
     /// Normally, dropping a runtime will block indefinitely for spawned blocking tasks
@@ -370,6 +384,8 @@ impl Runtime {
     /// may result in a resource leak (in that any blocking tasks are still running until they
     /// return.
     ///
+    /// See the [struct level documentation](Runtime#shutdown) for more details.
+    ///
     /// This function is equivalent to calling `shutdown_timeout(Duration::from_nanos(0))`.
     ///
     /// ```
diff --git a/tokio/src/runtime/scheduler/multi_thread/queue.rs b/tokio/src/runtime/scheduler/multi_thread/queue.rs
index 59b448d26b8..faf56db2e91 100644
--- a/tokio/src/runtime/scheduler/multi_thread/queue.rs
+++ b/tokio/src/runtime/scheduler/multi_thread/queue.rs
@@ -263,7 +263,7 @@ impl<T> Local<T> {
         // safety: The CAS above ensures that no consumer will look at these
         // values again, and we are the only producer.
         let batch_iter = BatchTaskIter {
-            buffer: &*self.inner.buffer,
+            buffer: &self.inner.buffer,
             head: head as UnsignedLong,
             i: 0,
         };
@@ -353,6 +353,7 @@ impl<T> Steal<T> {
         }
 
         dst_metrics.incr_steal_count(n as u16);
+        dst_metrics.incr_steal_operations();
 
         // We are returning a task here
         n -= 1;
diff --git a/tokio/src/runtime/task/harness.rs b/tokio/src/runtime/task/harness.rs
index c0792979844..8e3c3d14fa0 100644
--- a/tokio/src/runtime/task/harness.rs
+++ b/tokio/src/runtime/task/harness.rs
@@ -194,7 +194,7 @@ where
             TransitionToRunning::Success => {
                 let header_ptr = self.header_ptr();
                 let waker_ref = waker_ref::<T, S>(&header_ptr);
-                let cx = Context::from_waker(&*waker_ref);
+                let cx = Context::from_waker(&waker_ref);
                 let res = poll_future(self.core(), cx);
 
                 if res == Poll::Ready(()) {
@@ -315,9 +315,10 @@ where
                 // this task. It is our responsibility to drop the
                 // output.
                 self.core().drop_future_or_output();
-            } else if snapshot.has_join_waker() {
-                // Notify the join handle. The previous transition obtains the
-                // lock on the waker cell.
+            } else if snapshot.is_join_waker_set() {
+                // Notify the waker. Reading the waker field is safe per rule 4
+                // in task/mod.rs, since the JOIN_WAKER bit is set and the call
+                // to transition_to_complete() above set the COMPLETE bit.
                 self.trailer().wake_join();
             }
         }));
@@ -367,36 +368,30 @@ fn can_read_output(header: &Header, trailer: &Trailer, waker: &Waker) -> bool {
     debug_assert!(snapshot.is_join_interested());
 
     if !snapshot.is_complete() {
-        // The waker must be stored in the task struct.
-        let res = if snapshot.has_join_waker() {
-            // There already is a waker stored in the struct. If it matches
-            // the provided waker, then there is no further work to do.
-            // Otherwise, the waker must be swapped.
-            let will_wake = unsafe {
-                // Safety: when `JOIN_INTEREST` is set, only `JOIN_HANDLE`
-                // may mutate the `waker` field.
-                trailer.will_wake(waker)
-            };
-
-            if will_wake {
-                // The task is not complete **and** the waker is up to date,
-                // there is nothing further that needs to be done.
+        // If the task is not complete, try storing the provided waker in the
+        // task's waker field.
+
+        let res = if snapshot.is_join_waker_set() {
+            // If JOIN_WAKER is set, then JoinHandle has previously stored a
+            // waker in the waker field per step (iii) of rule 5 in task/mod.rs.
+
+            // Optimization: if the stored waker and the provided waker wake the
+            // same task, then return without touching the waker field. (Reading
+            // the waker field below is safe per rule 3 in task/mod.rs.)
+            if unsafe { trailer.will_wake(waker) } {
                 return false;
             }
 
-            // Unset the `JOIN_WAKER` to gain mutable access to the `waker`
-            // field then update the field with the new join worker.
-            //
-            // This requires two atomic operations, unsetting the bit and
-            // then resetting it. If the task transitions to complete
-            // concurrently to either one of those operations, then setting
-            // the join waker fails and we proceed to reading the task
-            // output.
+            // Otherwise swap the stored waker with the provided waker by
+            // following the rule 5 in task/mod.rs.
             header
                 .state
                 .unset_waker()
                 .and_then(|snapshot| set_join_waker(header, trailer, waker.clone(), snapshot))
         } else {
+            // If JOIN_WAKER is unset, then JoinHandle has mutable access to the
+            // waker field per rule 2 in task/mod.rs; therefore, skip step (i)
+            // of rule 5 and try to store the provided waker in the waker field.
             set_join_waker(header, trailer, waker.clone(), snapshot)
         };
 
@@ -417,7 +412,7 @@ fn set_join_waker(
     snapshot: Snapshot,
 ) -> Result<Snapshot, Snapshot> {
     assert!(snapshot.is_join_interested());
-    assert!(!snapshot.has_join_waker());
+    assert!(!snapshot.is_join_waker_set());
 
     // Safety: Only the `JoinHandle` may set the `waker` field. When
     // `JOIN_INTEREST` is **not** set, nothing else will touch the field.
diff --git a/tokio/src/runtime/task/id.rs b/tokio/src/runtime/task/id.rs
new file mode 100644
index 00000000000..2b0d95c0243
--- /dev/null
+++ b/tokio/src/runtime/task/id.rs
@@ -0,0 +1,87 @@
+use crate::runtime::context;
+
+use std::fmt;
+
+/// An opaque ID that uniquely identifies a task relative to all other currently
+/// running tasks.
+///
+/// # Notes
+///
+/// - Task IDs are unique relative to other *currently running* tasks. When a
+///   task completes, the same ID may be used for another task.
+/// - Task IDs are *not* sequential, and do not indicate the order in which
+///   tasks are spawned, what runtime a task is spawned on, or any other data.
+/// - The task ID of the currently running task can be obtained from inside the
+///   task via the [`task::try_id()`](crate::task::try_id()) and
+///   [`task::id()`](crate::task::id()) functions and from outside the task via
+///   the [`JoinHandle::id()`](crate::task::JoinHandle::id()) function.
+///
+/// **Note**: This is an [unstable API][unstable]. The public API of this type
+/// may break in 1.x releases. See [the documentation on unstable
+/// features][unstable] for details.
+///
+/// [unstable]: crate#unstable-features
+#[cfg_attr(docsrs, doc(cfg(all(feature = "rt", tokio_unstable))))]
+#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
+#[derive(Clone, Copy, Debug, Hash, Eq, PartialEq)]
+pub struct Id(u64);
+
+/// Returns the [`Id`] of the currently running task.
+///
+/// # Panics
+///
+/// This function panics if called from outside a task. Please note that calls
+/// to `block_on` do not have task IDs, so the method will panic if called from
+/// within a call to `block_on`. For a version of this function that doesn't
+/// panic, see [`task::try_id()`](crate::runtime::task::try_id()).
+///
+/// **Note**: This is an [unstable API][unstable]. The public API of this type
+/// may break in 1.x releases. See [the documentation on unstable
+/// features][unstable] for details.
+///
+/// [task ID]: crate::task::Id
+/// [unstable]: crate#unstable-features
+#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
+#[track_caller]
+pub fn id() -> Id {
+    context::current_task_id().expect("Can't get a task id when not inside a task")
+}
+
+/// Returns the [`Id`] of the currently running task, or `None` if called outside
+/// of a task.
+///
+/// This function is similar to  [`task::id()`](crate::runtime::task::id()), except
+/// that it returns `None` rather than panicking if called outside of a task
+/// context.
+///
+/// **Note**: This is an [unstable API][unstable]. The public API of this type
+/// may break in 1.x releases. See [the documentation on unstable
+/// features][unstable] for details.
+///
+/// [task ID]: crate::task::Id
+/// [unstable]: crate#unstable-features
+#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
+#[track_caller]
+pub fn try_id() -> Option<Id> {
+    context::current_task_id()
+}
+
+impl fmt::Display for Id {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl Id {
+    pub(crate) fn next() -> Self {
+        use crate::loom::sync::atomic::{Ordering::Relaxed, StaticAtomicU64};
+
+        static NEXT_ID: StaticAtomicU64 = StaticAtomicU64::new(1);
+
+        Self(NEXT_ID.fetch_add(1, Relaxed))
+    }
+
+    pub(crate) fn as_u64(&self) -> u64 {
+        self.0
+    }
+}
diff --git a/tokio/src/runtime/task/join.rs b/tokio/src/runtime/task/join.rs
index 5660575504e..11c4b9ba311 100644
--- a/tokio/src/runtime/task/join.rs
+++ b/tokio/src/runtime/task/join.rs
@@ -11,9 +11,9 @@ cfg_rt! {
     /// An owned permission to join on a task (await its termination).
     ///
     /// This can be thought of as the equivalent of [`std::thread::JoinHandle`]
-    /// for a Tokio task rather than a thread. You do not need to `.await` the
-    /// `JoinHandle` to make the task execute — it will start running in the
-    /// background immediately.
+    /// for a Tokio task rather than a thread. Note that the background task
+    /// associated with this `JoinHandle` started running immediately when you
+    /// called spawn, even if you have not yet awaited the `JoinHandle`.
     ///
     /// A `JoinHandle` *detaches* the associated task when it is dropped, which
     /// means that there is no longer any handle to the task, and no way to `join`
diff --git a/tokio/src/runtime/task/mod.rs b/tokio/src/runtime/task/mod.rs
index fea6e0faada..55131ac5665 100644
--- a/tokio/src/runtime/task/mod.rs
+++ b/tokio/src/runtime/task/mod.rs
@@ -168,19 +168,20 @@
 // unstable. This should be removed once `JoinSet` is stabilized.
 #![cfg_attr(not(tokio_unstable), allow(dead_code))]
 
-use crate::runtime::context;
-
 mod core;
 use self::core::Cell;
 use self::core::Header;
 
 mod error;
-#[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
 pub use self::error::JoinError;
 
 mod harness;
 use self::harness::Harness;
 
+mod id;
+#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
+pub use id::{id, try_id, Id};
+
 cfg_rt_multi_thread! {
     mod inject;
     pub(super) use self::inject::Inject;
@@ -191,10 +192,8 @@ mod abort;
 mod join;
 
 #[cfg(feature = "rt")]
-#[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
 pub use self::abort::AbortHandle;
 
-#[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
 pub use self::join::JoinHandle;
 
 mod list;
@@ -215,70 +214,6 @@ use std::marker::PhantomData;
 use std::ptr::NonNull;
 use std::{fmt, mem};
 
-/// An opaque ID that uniquely identifies a task relative to all other currently
-/// running tasks.
-///
-/// # Notes
-///
-/// - Task IDs are unique relative to other *currently running* tasks. When a
-///   task completes, the same ID may be used for another task.
-/// - Task IDs are *not* sequential, and do not indicate the order in which
-///   tasks are spawned, what runtime a task is spawned on, or any other data.
-/// - The task ID of the currently running task can be obtained from inside the
-///   task via the [`task::try_id()`](crate::task::try_id()) and
-///   [`task::id()`](crate::task::id()) functions and from outside the task via
-///   the [`JoinHandle::id()`](crate::task::JoinHandle::id()) function.
-///
-/// **Note**: This is an [unstable API][unstable]. The public API of this type
-/// may break in 1.x releases. See [the documentation on unstable
-/// features][unstable] for details.
-///
-/// [unstable]: crate#unstable-features
-#[cfg_attr(docsrs, doc(cfg(all(feature = "rt", tokio_unstable))))]
-#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
-#[derive(Clone, Copy, Debug, Hash, Eq, PartialEq)]
-pub struct Id(u64);
-
-/// Returns the [`Id`] of the currently running task.
-///
-/// # Panics
-///
-/// This function panics if called from outside a task. Please note that calls
-/// to `block_on` do not have task IDs, so the method will panic if called from
-/// within a call to `block_on`. For a version of this function that doesn't
-/// panic, see [`task::try_id()`](crate::runtime::task::try_id()).
-///
-/// **Note**: This is an [unstable API][unstable]. The public API of this type
-/// may break in 1.x releases. See [the documentation on unstable
-/// features][unstable] for details.
-///
-/// [task ID]: crate::task::Id
-/// [unstable]: crate#unstable-features
-#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
-#[track_caller]
-pub fn id() -> Id {
-    context::current_task_id().expect("Can't get a task id when not inside a task")
-}
-
-/// Returns the [`Id`] of the currently running task, or `None` if called outside
-/// of a task.
-///
-/// This function is similar to  [`task::id()`](crate::runtime::task::id()), except
-/// that it returns `None` rather than panicking if called outside of a task
-/// context.
-///
-/// **Note**: This is an [unstable API][unstable]. The public API of this type
-/// may break in 1.x releases. See [the documentation on unstable
-/// features][unstable] for details.
-///
-/// [task ID]: crate::task::Id
-/// [unstable]: crate#unstable-features
-#[cfg_attr(not(tokio_unstable), allow(unreachable_pub))]
-#[track_caller]
-pub fn try_id() -> Option<Id> {
-    context::current_task_id()
-}
-
 /// An owned handle to the task, tracked by ref count.
 #[repr(transparent)]
 pub(crate) struct Task<S: 'static> {
@@ -554,66 +489,3 @@ unsafe impl<S> linked_list::Link for Task<S> {
         self::core::Trailer::addr_of_owned(Header::get_trailer(target))
     }
 }
-
-impl fmt::Display for Id {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.0.fmt(f)
-    }
-}
-
-impl Id {
-    // When 64-bit atomics are available, use a static `AtomicU64` counter to
-    // generate task IDs.
-    //
-    // Note(eliza): we _could_ just use `crate::loom::AtomicU64`, which switches
-    // between an atomic and mutex-based implementation here, rather than having
-    // two separate functions for targets with and without 64-bit atomics.
-    // However, because we can't use the mutex-based implementation in a static
-    // initializer directly, the 32-bit impl also has to use a `OnceCell`, and I
-    // thought it was nicer to avoid the `OnceCell` overhead on 64-bit
-    // platforms...
-    cfg_has_atomic_u64! {
-        pub(crate) fn next() -> Self {
-            use std::sync::atomic::{AtomicU64, Ordering::Relaxed};
-            static NEXT_ID: AtomicU64 = AtomicU64::new(1);
-            Self(NEXT_ID.fetch_add(1, Relaxed))
-        }
-    }
-
-    cfg_not_has_atomic_u64! {
-        cfg_has_const_mutex_new! {
-            pub(crate) fn next() -> Self {
-                use crate::loom::sync::Mutex;
-                static NEXT_ID: Mutex<u64> = Mutex::const_new(1);
-
-                let mut lock = NEXT_ID.lock();
-                let id = *lock;
-                *lock += 1;
-                Self(id)
-            }
-        }
-
-        cfg_not_has_const_mutex_new! {
-            pub(crate) fn next() -> Self {
-                use crate::util::once_cell::OnceCell;
-                use crate::loom::sync::Mutex;
-
-                fn init_next_id() -> Mutex<u64> {
-                    Mutex::new(1)
-                }
-
-                static NEXT_ID: OnceCell<Mutex<u64>> = OnceCell::new();
-
-                let next_id = NEXT_ID.get(init_next_id);
-                let mut lock = next_id.lock();
-                let id = *lock;
-                *lock += 1;
-                Self(id)
-            }
-        }
-    }
-
-    pub(crate) fn as_u64(&self) -> u64 {
-        self.0
-    }
-}
diff --git a/tokio/src/runtime/task/state.rs b/tokio/src/runtime/task/state.rs
index c2d5b28eac2..77283125e61 100644
--- a/tokio/src/runtime/task/state.rs
+++ b/tokio/src/runtime/task/state.rs
@@ -378,7 +378,7 @@ impl State {
     pub(super) fn set_join_waker(&self) -> UpdateResult {
         self.fetch_update(|curr| {
             assert!(curr.is_join_interested());
-            assert!(!curr.has_join_waker());
+            assert!(!curr.is_join_waker_set());
 
             if curr.is_complete() {
                 return None;
@@ -398,7 +398,7 @@ impl State {
     pub(super) fn unset_waker(&self) -> UpdateResult {
         self.fetch_update(|curr| {
             assert!(curr.is_join_interested());
-            assert!(curr.has_join_waker());
+            assert!(curr.is_join_waker_set());
 
             if curr.is_complete() {
                 return None;
@@ -546,7 +546,7 @@ impl Snapshot {
         self.0 &= !JOIN_INTEREST
     }
 
-    pub(super) fn has_join_waker(self) -> bool {
+    pub(super) fn is_join_waker_set(self) -> bool {
         self.0 & JOIN_WAKER == JOIN_WAKER
     }
 
@@ -588,7 +588,7 @@ impl fmt::Debug for Snapshot {
             .field("is_notified", &self.is_notified())
             .field("is_cancelled", &self.is_cancelled())
             .field("is_join_interested", &self.is_join_interested())
-            .field("has_join_waker", &self.has_join_waker())
+            .field("is_join_waker_set", &self.is_join_waker_set())
             .field("ref_count", &self.ref_count())
             .finish()
     }
diff --git a/tokio/src/runtime/tests/loom_blocking.rs b/tokio/src/runtime/tests/loom_blocking.rs
index 89de85e4362..5c4aeae39c5 100644
--- a/tokio/src/runtime/tests/loom_blocking.rs
+++ b/tokio/src/runtime/tests/loom_blocking.rs
@@ -73,6 +73,27 @@ fn spawn_mandatory_blocking_should_run_even_when_shutting_down_from_other_thread
     });
 }
 
+#[test]
+fn spawn_blocking_when_paused() {
+    use std::time::Duration;
+    loom::model(|| {
+        let rt = crate::runtime::Builder::new_current_thread()
+            .enable_time()
+            .start_paused(true)
+            .build()
+            .unwrap();
+        let handle = rt.handle();
+        let _enter = handle.enter();
+        let a = crate::task::spawn_blocking(|| {});
+        let b = crate::task::spawn_blocking(|| {});
+        rt.block_on(crate::time::timeout(Duration::from_millis(1), async move {
+            a.await.expect("blocking task should finish");
+            b.await.expect("blocking task should finish");
+        }))
+        .expect("timeout should not trigger");
+    });
+}
+
 fn mk_runtime(num_threads: usize) -> Runtime {
     runtime::Builder::new_multi_thread()
         .worker_threads(num_threads)
diff --git a/tokio/src/runtime/tests/loom_queue.rs b/tokio/src/runtime/tests/loom_queue.rs
index 8d4e1d384e2..fc93bf3e4a2 100644
--- a/tokio/src/runtime/tests/loom_queue.rs
+++ b/tokio/src/runtime/tests/loom_queue.rs
@@ -1,6 +1,6 @@
-use crate::runtime::blocking::NoopSchedule;
 use crate::runtime::scheduler::multi_thread::queue;
 use crate::runtime::task::Inject;
+use crate::runtime::tests::NoopSchedule;
 use crate::runtime::MetricsBatch;
 
 use loom::thread;
diff --git a/tokio/src/runtime/tests/mod.rs b/tokio/src/runtime/tests/mod.rs
index 1c67dfefb32..4e7c2453f25 100644
--- a/tokio/src/runtime/tests/mod.rs
+++ b/tokio/src/runtime/tests/mod.rs
@@ -2,11 +2,29 @@
 // other code when running loom tests.
 #![cfg_attr(loom, warn(dead_code, unreachable_pub))]
 
+use self::noop_scheduler::NoopSchedule;
 use self::unowned_wrapper::unowned;
 
+mod noop_scheduler {
+    use crate::runtime::task::{self, Task};
+
+    /// `task::Schedule` implementation that does nothing, for testing.
+    pub(crate) struct NoopSchedule;
+
+    impl task::Schedule for NoopSchedule {
+        fn release(&self, _task: &Task<Self>) -> Option<Task<Self>> {
+            None
+        }
+
+        fn schedule(&self, _task: task::Notified<Self>) {
+            unreachable!();
+        }
+    }
+}
+
 mod unowned_wrapper {
-    use crate::runtime::blocking::NoopSchedule;
     use crate::runtime::task::{Id, JoinHandle, Notified};
+    use crate::runtime::tests::NoopSchedule;
 
     #[cfg(all(tokio_unstable, feature = "tracing"))]
     pub(crate) fn unowned<T>(task: T) -> (Notified<NoopSchedule>, JoinHandle<T::Output>)
diff --git a/tokio/src/runtime/tests/task.rs b/tokio/src/runtime/tests/task.rs
index 173e5b0b23f..a79c0f50d15 100644
--- a/tokio/src/runtime/tests/task.rs
+++ b/tokio/src/runtime/tests/task.rs
@@ -1,5 +1,5 @@
-use crate::runtime::blocking::NoopSchedule;
 use crate::runtime::task::{self, unowned, Id, JoinHandle, OwnedTasks, Schedule, Task};
+use crate::runtime::tests::NoopSchedule;
 use crate::util::TryLock;
 
 use std::collections::VecDeque;
diff --git a/tokio/src/runtime/thread_id.rs b/tokio/src/runtime/thread_id.rs
new file mode 100644
index 00000000000..ef392897963
--- /dev/null
+++ b/tokio/src/runtime/thread_id.rs
@@ -0,0 +1,31 @@
+use std::num::NonZeroU64;
+
+#[derive(Eq, PartialEq, Clone, Copy, Hash, Debug)]
+pub(crate) struct ThreadId(NonZeroU64);
+
+impl ThreadId {
+    pub(crate) fn next() -> Self {
+        use crate::loom::sync::atomic::{Ordering::Relaxed, StaticAtomicU64};
+
+        static NEXT_ID: StaticAtomicU64 = StaticAtomicU64::new(0);
+
+        let mut last = NEXT_ID.load(Relaxed);
+        loop {
+            let id = match last.checked_add(1) {
+                Some(id) => id,
+                None => exhausted(),
+            };
+
+            match NEXT_ID.compare_exchange_weak(last, id, Relaxed, Relaxed) {
+                Ok(_) => return ThreadId(NonZeroU64::new(id).unwrap()),
+                Err(id) => last = id,
+            }
+        }
+    }
+}
+
+#[cold]
+#[allow(dead_code)]
+fn exhausted() -> ! {
+    panic!("failed to generate unique thread ID: bitspace exhausted")
+}
diff --git a/tokio/src/runtime/time/entry.rs b/tokio/src/runtime/time/entry.rs
index f0d613a3bb4..f86d9ed97f0 100644
--- a/tokio/src/runtime/time/entry.rs
+++ b/tokio/src/runtime/time/entry.rs
@@ -94,7 +94,7 @@ pub(super) struct StateCell {
     /// without holding the driver lock is undefined behavior.
     result: UnsafeCell<TimerResult>,
     /// The currently-registered waker
-    waker: CachePadded<AtomicWaker>,
+    waker: AtomicWaker,
 }
 
 impl Default for StateCell {
@@ -114,7 +114,7 @@ impl StateCell {
         Self {
             state: AtomicU64::new(STATE_DEREGISTERED),
             result: UnsafeCell::new(Ok(())),
-            waker: CachePadded(AtomicWaker::new()),
+            waker: AtomicWaker::new(),
         }
     }
 
@@ -139,7 +139,7 @@ impl StateCell {
         // We must register first. This ensures that either `fire` will
         // observe the new waker, or we will observe a racing fire to have set
         // the state, or both.
-        self.waker.0.register_by_ref(waker);
+        self.waker.register_by_ref(waker);
 
         self.read_state()
     }
@@ -227,7 +227,7 @@ impl StateCell {
 
         self.state.store(STATE_DEREGISTERED, Ordering::Release);
 
-        self.waker.0.take_waker()
+        self.waker.take_waker()
     }
 
     /// Marks the timer as registered (poll will return None) and sets the
@@ -298,9 +298,11 @@ pub(crate) struct TimerEntry {
     /// This is manipulated only under the inner mutex. TODO: Can we use loom
     /// cells for this?
     inner: StdUnsafeCell<TimerShared>,
-    /// Initial deadline for the timer. This is used to register on the first
+    /// Deadline for the timer. This is used to register on the first
     /// poll, as we can't register prior to being pinned.
-    initial_deadline: Option<Instant>,
+    deadline: Instant,
+    /// Whether the deadline has been registered.
+    registered: bool,
     /// Ensure the type is !Unpin
     _m: std::marker::PhantomPinned,
 }
@@ -329,11 +331,20 @@ pub(super) type EntryList = crate::util::linked_list::LinkedList<TimerShared, Ti
 /// frontend (`Entry`) and driver backend.
 ///
 /// Note that this structure is located inside the `TimerEntry` structure.
-#[derive(Debug)]
-#[repr(C)]
 pub(crate) struct TimerShared {
-    /// Data manipulated by the driver thread itself, only.
-    driver_state: CachePadded<TimerSharedPadded>,
+    /// A link within the doubly-linked list of timers on a particular level and
+    /// slot. Valid only if state is equal to Registered.
+    ///
+    /// Only accessed under the entry lock.
+    pointers: linked_list::Pointers<TimerShared>,
+
+    /// The expiration time for which this entry is currently registered.
+    /// Generally owned by the driver, but is accessed by the entry when not
+    /// registered.
+    cached_when: AtomicU64,
+
+    /// The true expiration time. Set by the timer future, read by the driver.
+    true_when: AtomicU64,
 
     /// Current state. This records whether the timer entry is currently under
     /// the ownership of the driver, and if not, its current state (not
@@ -343,10 +354,23 @@ pub(crate) struct TimerShared {
     _p: PhantomPinned,
 }
 
+unsafe impl Send for TimerShared {}
+unsafe impl Sync for TimerShared {}
+
+impl std::fmt::Debug for TimerShared {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("TimerShared")
+            .field("when", &self.true_when.load(Ordering::Relaxed))
+            .field("cached_when", &self.cached_when.load(Ordering::Relaxed))
+            .field("state", &self.state)
+            .finish()
+    }
+}
+
 generate_addr_of_methods! {
     impl<> TimerShared {
         unsafe fn addr_of_pointers(self: NonNull<Self>) -> NonNull<linked_list::Pointers<TimerShared>> {
-            &self.driver_state.0.pointers
+            &self.pointers
         }
     }
 }
@@ -354,8 +378,10 @@ generate_addr_of_methods! {
 impl TimerShared {
     pub(super) fn new() -> Self {
         Self {
+            cached_when: AtomicU64::new(0),
+            true_when: AtomicU64::new(0),
+            pointers: linked_list::Pointers::new(),
             state: StateCell::default(),
-            driver_state: CachePadded(TimerSharedPadded::new()),
             _p: PhantomPinned,
         }
     }
@@ -363,7 +389,7 @@ impl TimerShared {
     /// Gets the cached time-of-expiration value.
     pub(super) fn cached_when(&self) -> u64 {
         // Cached-when is only accessed under the driver lock, so we can use relaxed
-        self.driver_state.0.cached_when.load(Ordering::Relaxed)
+        self.cached_when.load(Ordering::Relaxed)
     }
 
     /// Gets the true time-of-expiration value, and copies it into the cached
@@ -374,10 +400,7 @@ impl TimerShared {
     pub(super) unsafe fn sync_when(&self) -> u64 {
         let true_when = self.true_when();
 
-        self.driver_state
-            .0
-            .cached_when
-            .store(true_when, Ordering::Relaxed);
+        self.cached_when.store(true_when, Ordering::Relaxed);
 
         true_when
     }
@@ -387,10 +410,7 @@ impl TimerShared {
     /// SAFETY: Must be called with the driver lock held, and when this entry is
     /// not in any timer wheel lists.
     unsafe fn set_cached_when(&self, when: u64) {
-        self.driver_state
-            .0
-            .cached_when
-            .store(when, Ordering::Relaxed);
+        self.cached_when.store(when, Ordering::Relaxed);
     }
 
     /// Returns the true time-of-expiration value, with relaxed memory ordering.
@@ -405,7 +425,7 @@ impl TimerShared {
     /// in the timer wheel.
     pub(super) unsafe fn set_expiration(&self, t: u64) {
         self.state.set_expiration(t);
-        self.driver_state.0.cached_when.store(t, Ordering::Relaxed);
+        self.cached_when.store(t, Ordering::Relaxed);
     }
 
     /// Sets the true time-of-expiration only if it is after the current.
@@ -429,48 +449,6 @@ impl TimerShared {
     }
 }
 
-/// Additional shared state between the driver and the timer which is cache
-/// padded. This contains the information that the driver thread accesses most
-/// frequently to minimize contention. In particular, we move it away from the
-/// waker, as the waker is updated on every poll.
-struct TimerSharedPadded {
-    /// A link within the doubly-linked list of timers on a particular level and
-    /// slot. Valid only if state is equal to Registered.
-    ///
-    /// Only accessed under the entry lock.
-    pointers: linked_list::Pointers<TimerShared>,
-
-    /// The expiration time for which this entry is currently registered.
-    /// Generally owned by the driver, but is accessed by the entry when not
-    /// registered.
-    cached_when: AtomicU64,
-
-    /// The true expiration time. Set by the timer future, read by the driver.
-    true_when: AtomicU64,
-}
-
-impl std::fmt::Debug for TimerSharedPadded {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        f.debug_struct("TimerSharedPadded")
-            .field("when", &self.true_when.load(Ordering::Relaxed))
-            .field("cached_when", &self.cached_when.load(Ordering::Relaxed))
-            .finish()
-    }
-}
-
-impl TimerSharedPadded {
-    fn new() -> Self {
-        Self {
-            cached_when: AtomicU64::new(0),
-            true_when: AtomicU64::new(0),
-            pointers: linked_list::Pointers::new(),
-        }
-    }
-}
-
-unsafe impl Send for TimerShared {}
-unsafe impl Sync for TimerShared {}
-
 unsafe impl linked_list::Link for TimerShared {
     type Handle = TimerHandle;
 
@@ -504,7 +482,8 @@ impl TimerEntry {
         Self {
             driver,
             inner: StdUnsafeCell::new(TimerShared::new()),
-            initial_deadline: Some(deadline),
+            deadline,
+            registered: false,
             _m: std::marker::PhantomPinned,
         }
     }
@@ -513,8 +492,12 @@ impl TimerEntry {
         unsafe { &*self.inner.get() }
     }
 
+    pub(crate) fn deadline(&self) -> Instant {
+        self.deadline
+    }
+
     pub(crate) fn is_elapsed(&self) -> bool {
-        !self.inner().state.might_be_registered() && self.initial_deadline.is_none()
+        !self.inner().state.might_be_registered() && self.registered
     }
 
     /// Cancels and deregisters the timer. This operation is irreversible.
@@ -545,7 +528,8 @@ impl TimerEntry {
     }
 
     pub(crate) fn reset(mut self: Pin<&mut Self>, new_time: Instant) {
-        unsafe { self.as_mut().get_unchecked_mut() }.initial_deadline = None;
+        unsafe { self.as_mut().get_unchecked_mut() }.deadline = new_time;
+        unsafe { self.as_mut().get_unchecked_mut() }.registered = true;
 
         let tick = self.driver().time_source().deadline_to_tick(new_time);
 
@@ -567,7 +551,8 @@ impl TimerEntry {
             panic!("{}", crate::util::error::RUNTIME_SHUTTING_DOWN_ERROR);
         }
 
-        if let Some(deadline) = self.initial_deadline {
+        if !self.registered {
+            let deadline = self.deadline;
             self.as_mut().reset(deadline);
         }
 
@@ -579,6 +564,11 @@ impl TimerEntry {
     pub(crate) fn driver(&self) -> &super::Handle {
         self.driver.driver().time()
     }
+
+    #[cfg(all(tokio_unstable, feature = "tracing"))]
+    pub(crate) fn clock(&self) -> &super::Clock {
+        self.driver.driver().clock()
+    }
 }
 
 impl TimerHandle {
@@ -646,74 +636,3 @@ impl Drop for TimerEntry {
         unsafe { Pin::new_unchecked(self) }.as_mut().cancel()
     }
 }
-
-// Copied from [crossbeam/cache_padded](https://github.com/crossbeam-rs/crossbeam/blob/fa35346b7c789bba045ad789e894c68c466d1779/crossbeam-utils/src/cache_padded.rs#L62-L127)
-//
-// Starting from Intel's Sandy Bridge, spatial prefetcher is now pulling pairs of 64-byte cache
-// lines at a time, so we have to align to 128 bytes rather than 64.
-//
-// Sources:
-// - https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-optimization-manual.pdf
-// - https://github.com/facebook/folly/blob/1b5288e6eea6df074758f877c849b6e73bbb9fbb/folly/lang/Align.h#L107
-//
-// ARM's big.LITTLE architecture has asymmetric cores and "big" cores have 128-byte cache line size.
-//
-// Sources:
-// - https://www.mono-project.com/news/2016/09/12/arm64-icache/
-//
-// powerpc64 has 128-byte cache line size.
-//
-// Sources:
-// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_ppc64x.go#L9
-#[cfg_attr(
-    any(
-        target_arch = "x86_64",
-        target_arch = "aarch64",
-        target_arch = "powerpc64",
-    ),
-    repr(align(128))
-)]
-// arm, mips, mips64, and riscv64 have 32-byte cache line size.
-//
-// Sources:
-// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_arm.go#L7
-// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_mips.go#L7
-// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_mipsle.go#L7
-// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_mips64x.go#L9
-// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_riscv64.go#L7
-#[cfg_attr(
-    any(
-        target_arch = "arm",
-        target_arch = "mips",
-        target_arch = "mips64",
-        target_arch = "riscv64",
-    ),
-    repr(align(32))
-)]
-// s390x has 256-byte cache line size.
-//
-// Sources:
-// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_s390x.go#L7
-#[cfg_attr(target_arch = "s390x", repr(align(256)))]
-// x86 and wasm have 64-byte cache line size.
-//
-// Sources:
-// - https://github.com/golang/go/blob/dda2991c2ea0c5914714469c4defc2562a907230/src/internal/cpu/cpu_x86.go#L9
-// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_wasm.go#L7
-//
-// All others are assumed to have 64-byte cache line size.
-#[cfg_attr(
-    not(any(
-        target_arch = "x86_64",
-        target_arch = "aarch64",
-        target_arch = "powerpc64",
-        target_arch = "arm",
-        target_arch = "mips",
-        target_arch = "mips64",
-        target_arch = "riscv64",
-        target_arch = "s390x",
-    )),
-    repr(align(64))
-)]
-#[derive(Debug, Default)]
-struct CachePadded<T>(T);
diff --git a/tokio/src/runtime/time/mod.rs b/tokio/src/runtime/time/mod.rs
index 240f8f16e6d..215714dd576 100644
--- a/tokio/src/runtime/time/mod.rs
+++ b/tokio/src/runtime/time/mod.rs
@@ -125,7 +125,7 @@ impl Driver {
     /// thread and `time_source` to get the current time and convert to ticks.
     ///
     /// Specifying the source of time is useful when testing.
-    pub(crate) fn new(park: IoStack, clock: Clock) -> (Driver, Handle) {
+    pub(crate) fn new(park: IoStack, clock: &Clock) -> (Driver, Handle) {
         let time_source = TimeSource::new(clock);
 
         let handle = Handle {
@@ -186,7 +186,7 @@ impl Driver {
 
         match next_wake {
             Some(when) => {
-                let now = handle.time_source.now();
+                let now = handle.time_source.now(rt_handle.clock());
                 // Note that we effectively round up to 1ms here - this avoids
                 // very short-duration microsecond-resolution sleeps that the OS
                 // might treat as zero-length.
@@ -214,15 +214,15 @@ impl Driver {
         }
 
         // Process pending timers after waking up
-        handle.process();
+        handle.process(rt_handle.clock());
     }
 
     cfg_test_util! {
         fn park_thread_timeout(&mut self, rt_handle: &driver::Handle, duration: Duration) {
             let handle = rt_handle.time();
-            let clock = &handle.time_source.clock;
+            let clock = rt_handle.clock();
 
-            if clock.is_paused() {
+            if clock.can_auto_advance() {
                 self.park.park_timeout(rt_handle, Duration::from_secs(0));
 
                 // If the time driver was woken, then the park completed
@@ -231,7 +231,9 @@ impl Driver {
                 // advance the clock.
                 if !handle.did_wake() {
                     // Simulate advancing time
-                    clock.advance(duration);
+                    if let Err(msg) = clock.advance(duration) {
+                        panic!("{}", msg);
+                    }
                 }
             } else {
                 self.park.park_timeout(rt_handle, duration);
@@ -248,8 +250,8 @@ impl Driver {
 
 impl Handle {
     /// Runs timer related logic, and returns the next wakeup time
-    pub(self) fn process(&self) {
-        let now = self.time_source().now();
+    pub(self) fn process(&self, clock: &Clock) {
+        let now = self.time_source().now(clock);
 
         self.process_at_time(now)
     }
diff --git a/tokio/src/runtime/time/source.rs b/tokio/src/runtime/time/source.rs
index e6788edcaf8..39483b5c0ad 100644
--- a/tokio/src/runtime/time/source.rs
+++ b/tokio/src/runtime/time/source.rs
@@ -5,15 +5,13 @@ use std::convert::TryInto;
 /// A structure which handles conversion from Instants to u64 timestamps.
 #[derive(Debug)]
 pub(crate) struct TimeSource {
-    pub(crate) clock: Clock,
     start_time: Instant,
 }
 
 impl TimeSource {
-    pub(crate) fn new(clock: Clock) -> Self {
+    pub(crate) fn new(clock: &Clock) -> Self {
         Self {
             start_time: clock.now(),
-            clock,
         }
     }
 
@@ -36,7 +34,7 @@ impl TimeSource {
         Duration::from_millis(t)
     }
 
-    pub(crate) fn now(&self) -> u64 {
-        self.instant_to_tick(self.clock.now())
+    pub(crate) fn now(&self, clock: &Clock) -> u64 {
+        self.instant_to_tick(clock.now())
     }
 }
diff --git a/tokio/src/runtime/time/tests/mod.rs b/tokio/src/runtime/time/tests/mod.rs
index 88c7d768d46..2468a1ae67b 100644
--- a/tokio/src/runtime/time/tests/mod.rs
+++ b/tokio/src/runtime/time/tests/mod.rs
@@ -62,12 +62,13 @@ fn single_timer() {
 
         thread::yield_now();
 
-        let handle = handle.inner.driver().time();
+        let time = handle.inner.driver().time();
+        let clock = handle.inner.driver().clock();
 
         // This may or may not return Some (depending on how it races with the
         // thread). If it does return None, however, the timer should complete
         // synchronously.
-        handle.process_at_time(handle.time_source().now() + 2_000_000_000);
+        time.process_at_time(time.time_source().now(clock) + 2_000_000_000);
 
         jh.join().unwrap();
     })
@@ -97,10 +98,11 @@ fn drop_timer() {
 
         thread::yield_now();
 
-        let handle = handle.inner.driver().time();
+        let time = handle.inner.driver().time();
+        let clock = handle.inner.driver().clock();
 
         // advance 2s in the future.
-        handle.process_at_time(handle.time_source().now() + 2_000_000_000);
+        time.process_at_time(time.time_source().now(clock) + 2_000_000_000);
 
         jh.join().unwrap();
     })
@@ -132,10 +134,11 @@ fn change_waker() {
 
         thread::yield_now();
 
-        let handle = handle.inner.driver().time();
+        let time = handle.inner.driver().time();
+        let clock = handle.inner.driver().clock();
 
         // advance 2s
-        handle.process_at_time(handle.time_source().now() + 2_000_000_000);
+        time.process_at_time(time.time_source().now(clock) + 2_000_000_000);
 
         jh.join().unwrap();
     })
diff --git a/tokio/src/signal/registry.rs b/tokio/src/signal/registry.rs
index e1b3d108767..48e98c832fa 100644
--- a/tokio/src/signal/registry.rs
+++ b/tokio/src/signal/registry.rs
@@ -5,7 +5,6 @@ use crate::sync::watch;
 use crate::util::once_cell::OnceCell;
 
 use std::ops;
-use std::pin::Pin;
 use std::sync::atomic::{AtomicBool, Ordering};
 
 pub(crate) type EventId = usize;
@@ -162,14 +161,14 @@ where
     }
 }
 
-pub(crate) fn globals() -> Pin<&'static Globals>
+pub(crate) fn globals() -> &'static Globals
 where
     OsExtraData: 'static + Send + Sync + Init,
     OsStorage: 'static + Send + Sync + Init,
 {
     static GLOBALS: OnceCell<Globals> = OnceCell::new();
 
-    Pin::new(GLOBALS.get(globals_init))
+    GLOBALS.get(globals_init)
 }
 
 #[cfg(all(test, not(loom)))]
diff --git a/tokio/src/signal/unix.rs b/tokio/src/signal/unix.rs
index 0e1329ed54f..ae5c13085e9 100644
--- a/tokio/src/signal/unix.rs
+++ b/tokio/src/signal/unix.rs
@@ -14,7 +14,6 @@ use crate::sync::watch;
 
 use mio::net::UnixStream;
 use std::io::{self, Error, ErrorKind, Write};
-use std::pin::Pin;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Once;
 use std::task::{Context, Poll};
@@ -240,7 +239,7 @@ impl Default for SignalInfo {
 /// 2. Wake up the driver by writing a byte to a pipe
 ///
 /// Those two operations should both be async-signal safe.
-fn action(globals: Pin<&'static Globals>, signal: libc::c_int) {
+fn action(globals: &'static Globals, signal: libc::c_int) {
     globals.record_event(signal as EventId);
 
     // Send a wakeup, ignore any errors (anything reasonably possible is
@@ -293,7 +292,11 @@ fn signal_enable(signal: SignalKind, handle: &Handle) -> io::Result<()> {
     }
 }
 
-/// A stream of events for receiving a particular type of OS signal.
+/// An listener for receiving a particular type of OS signal.
+///
+/// The listener can be turned into a `Stream` using [`SignalStream`].
+///
+/// [`SignalStream`]: https://docs.rs/tokio-stream/latest/tokio_stream/wrappers/struct.SignalStream.html
 ///
 /// In general signal handling on Unix is a pretty tricky topic, and this
 /// structure is no exception! There are some important limitations to keep in
@@ -308,7 +311,7 @@ fn signal_enable(signal: SignalKind, handle: &Handle) -> io::Result<()> {
 ///   Once `poll` has been called, however, a further signal is guaranteed to
 ///   be yielded as an item.
 ///
-///   Put another way, any element pulled off the returned stream corresponds to
+///   Put another way, any element pulled off the returned listener corresponds to
 ///   *at least one* signal, but possibly more.
 ///
 /// * Signal handling in general is relatively inefficient. Although some
@@ -346,11 +349,11 @@ fn signal_enable(signal: SignalKind, handle: &Handle) -> io::Result<()> {
 /// #[tokio::main]
 /// async fn main() -> Result<(), Box<dyn std::error::Error>> {
 ///     // An infinite stream of hangup signals.
-///     let mut stream = signal(SignalKind::hangup())?;
+///     let mut sig = signal(SignalKind::hangup())?;
 ///
 ///     // Print whenever a HUP signal is received
 ///     loop {
-///         stream.recv().await;
+///         sig.recv().await;
 ///         println!("got signal HUP");
 ///     }
 /// }
@@ -361,7 +364,7 @@ pub struct Signal {
     inner: RxFuture,
 }
 
-/// Creates a new stream which will receive notifications when the current
+/// Creates a new listener which will receive notifications when the current
 /// process receives the specified signal `kind`.
 ///
 /// This function will create a new stream which binds to the default reactor.
diff --git a/tokio/src/signal/windows.rs b/tokio/src/signal/windows.rs
index 730f95d0591..2f70f98b15a 100644
--- a/tokio/src/signal/windows.rs
+++ b/tokio/src/signal/windows.rs
@@ -22,7 +22,7 @@ pub(crate) use self::imp::{OsExtraData, OsStorage};
 #[path = "windows/stub.rs"]
 mod imp;
 
-/// Creates a new stream which receives "ctrl-c" notifications sent to the
+/// Creates a new listener which receives "ctrl-c" notifications sent to the
 /// process.
 ///
 /// # Examples
@@ -32,12 +32,12 @@ mod imp;
 ///
 /// #[tokio::main]
 /// async fn main() -> Result<(), Box<dyn std::error::Error>> {
-///     // An infinite stream of CTRL-C events.
-///     let mut stream = ctrl_c()?;
+///     // A listener of CTRL-C events.
+///     let mut signal = ctrl_c()?;
 ///
 ///     // Print whenever a CTRL-C event is received.
 ///     for countdown in (0..3).rev() {
-///         stream.recv().await;
+///         signal.recv().await;
 ///         println!("got CTRL-C. {} more to exit", countdown);
 ///     }
 ///
@@ -50,14 +50,18 @@ pub fn ctrl_c() -> io::Result<CtrlC> {
     })
 }
 
-/// Represents a stream which receives "ctrl-c" notifications sent to the process
+/// Represents a listener which receives "ctrl-c" notifications sent to the process
 /// via `SetConsoleCtrlHandler`.
 ///
-/// A notification to this process notifies *all* streams listening for
+/// This event can be turned into a `Stream` using [`CtrlCStream`].
+///
+/// [`CtrlCStream`]: https://docs.rs/tokio-stream/latest/tokio_stream/wrappers/struct.CtrlCStream.html
+///
+/// A notification to this process notifies *all* receivers for
 /// this event. Moreover, the notifications **are coalesced** if they aren't processed
 /// quickly enough. This means that if two notifications are received back-to-back,
-/// then the stream may only receive one item about the two notifications.
-#[must_use = "streams do nothing unless polled"]
+/// then the listener may only receive one item about the two notifications.
+#[must_use = "listeners do nothing unless polled"]
 #[derive(Debug)]
 pub struct CtrlC {
     inner: RxFuture,
@@ -66,7 +70,7 @@ pub struct CtrlC {
 impl CtrlC {
     /// Receives the next signal notification event.
     ///
-    /// `None` is returned if no more events can be received by this stream.
+    /// `None` is returned if no more events can be received by the listener.
     ///
     /// # Examples
     ///
@@ -75,12 +79,11 @@ impl CtrlC {
     ///
     /// #[tokio::main]
     /// async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    ///     // An infinite stream of CTRL-C events.
-    ///     let mut stream = ctrl_c()?;
+    ///     let mut signal = ctrl_c()?;
     ///
     ///     // Print whenever a CTRL-C event is received.
     ///     for countdown in (0..3).rev() {
-    ///         stream.recv().await;
+    ///         signal.recv().await;
     ///         println!("got CTRL-C. {} more to exit", countdown);
     ///     }
     ///
@@ -94,7 +97,7 @@ impl CtrlC {
     /// Polls to receive the next signal notification event, outside of an
     /// `async` context.
     ///
-    /// `None` is returned if no more events can be received by this stream.
+    /// `None` is returned if no more events can be received.
     ///
     /// # Examples
     ///
@@ -124,14 +127,18 @@ impl CtrlC {
     }
 }
 
-/// Represents a stream which receives "ctrl-break" notifications sent to the process
+/// Represents a listener which receives "ctrl-break" notifications sent to the process
 /// via `SetConsoleCtrlHandler`.
 ///
-/// A notification to this process notifies *all* streams listening for
+/// This listener can be turned into a `Stream` using [`CtrlBreakStream`].
+///
+/// [`CtrlBreakStream`]: https://docs.rs/tokio-stream/latest/tokio_stream/wrappers/struct.CtrlBreakStream.html
+///
+/// A notification to this process notifies *all* receivers for
 /// this event. Moreover, the notifications **are coalesced** if they aren't processed
 /// quickly enough. This means that if two notifications are received back-to-back,
-/// then the stream may only receive one item about the two notifications.
-#[must_use = "streams do nothing unless polled"]
+/// then the listener may only receive one item about the two notifications.
+#[must_use = "listeners do nothing unless polled"]
 #[derive(Debug)]
 pub struct CtrlBreak {
     inner: RxFuture,
@@ -140,7 +147,7 @@ pub struct CtrlBreak {
 impl CtrlBreak {
     /// Receives the next signal notification event.
     ///
-    /// `None` is returned if no more events can be received by this stream.
+    /// `None` is returned if no more events can be received by this listener.
     ///
     /// # Examples
     ///
@@ -149,12 +156,12 @@ impl CtrlBreak {
     ///
     /// #[tokio::main]
     /// async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    ///     // An infinite stream of CTRL-BREAK events.
-    ///     let mut stream = ctrl_break()?;
+    ///     // A listener of CTRL-BREAK events.
+    ///     let mut signal = ctrl_break()?;
     ///
     ///     // Print whenever a CTRL-BREAK event is received.
     ///     loop {
-    ///         stream.recv().await;
+    ///         signal.recv().await;
     ///         println!("got signal CTRL-BREAK");
     ///     }
     /// }
@@ -166,7 +173,7 @@ impl CtrlBreak {
     /// Polls to receive the next signal notification event, outside of an
     /// `async` context.
     ///
-    /// `None` is returned if no more events can be received by this stream.
+    /// `None` is returned if no more events can be received by this listener.
     ///
     /// # Examples
     ///
@@ -196,7 +203,7 @@ impl CtrlBreak {
     }
 }
 
-/// Creates a new stream which receives "ctrl-break" notifications sent to the
+/// Creates a new listener which receives "ctrl-break" notifications sent to the
 /// process.
 ///
 /// # Examples
@@ -206,12 +213,12 @@ impl CtrlBreak {
 ///
 /// #[tokio::main]
 /// async fn main() -> Result<(), Box<dyn std::error::Error>> {
-///     // An infinite stream of CTRL-BREAK events.
-///     let mut stream = ctrl_break()?;
+///     // A listener of CTRL-BREAK events.
+///     let mut signal = ctrl_break()?;
 ///
 ///     // Print whenever a CTRL-BREAK event is received.
 ///     loop {
-///         stream.recv().await;
+///         signal.recv().await;
 ///         println!("got signal CTRL-BREAK");
 ///     }
 /// }
@@ -222,7 +229,7 @@ pub fn ctrl_break() -> io::Result<CtrlBreak> {
     })
 }
 
-/// Creates a new stream which receives "ctrl-close" notifications sent to the
+/// Creates a new listener which receives "ctrl-close" notifications sent to the
 /// process.
 ///
 /// # Examples
@@ -232,12 +239,12 @@ pub fn ctrl_break() -> io::Result<CtrlBreak> {
 ///
 /// #[tokio::main]
 /// async fn main() -> Result<(), Box<dyn std::error::Error>> {
-///     // An infinite stream of CTRL-CLOSE events.
-///     let mut stream = ctrl_close()?;
+///     // A listener of CTRL-CLOSE events.
+///     let mut signal = ctrl_close()?;
 ///
 ///     // Print whenever a CTRL-CLOSE event is received.
 ///     for countdown in (0..3).rev() {
-///         stream.recv().await;
+///         signal.recv().await;
 ///         println!("got CTRL-CLOSE. {} more to exit", countdown);
 ///     }
 ///
@@ -250,14 +257,14 @@ pub fn ctrl_close() -> io::Result<CtrlClose> {
     })
 }
 
-/// Represents a stream which receives "ctrl-close" notitifications sent to the process
+/// Represents a listener which receives "ctrl-close" notitifications sent to the process
 /// via 'SetConsoleCtrlHandler'.
 ///
-/// A notification to this process notifies *all* streams listening for
+/// A notification to this process notifies *all* listeners listening for
 /// this event. Moreover, the notifications **are coalesced** if they aren't processed
 /// quickly enough. This means that if two notifications are received back-to-back,
-/// then the stream may only receive one item about the two notifications.
-#[must_use = "streams do nothing unless polled"]
+/// then the listener may only receive one item about the two notifications.
+#[must_use = "listeners do nothing unless polled"]
 #[derive(Debug)]
 pub struct CtrlClose {
     inner: RxFuture,
@@ -266,7 +273,7 @@ pub struct CtrlClose {
 impl CtrlClose {
     /// Receives the next signal notification event.
     ///
-    /// `None` is returned if no more events can be received by this stream.
+    /// `None` is returned if no more events can be received by this listener.
     ///
     /// # Examples
     ///
@@ -275,11 +282,11 @@ impl CtrlClose {
     ///
     /// #[tokio::main]
     /// async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    ///     // An infinite stream of CTRL-CLOSE events.
-    ///     let mut stream = ctrl_close()?;
+    ///     // A listener of CTRL-CLOSE events.
+    ///     let mut signal = ctrl_close()?;
     ///
     ///     // Print whenever a CTRL-CLOSE event is received.
-    ///     stream.recv().await;
+    ///     signal.recv().await;
     ///     println!("got CTRL-CLOSE. Cleaning up before exiting");
     ///
     ///     Ok(())
@@ -292,7 +299,7 @@ impl CtrlClose {
     /// Polls to receive the next signal notification event, outside of an
     /// `async` context.
     ///
-    /// `None` is returned if no more events can be received by this stream.
+    /// `None` is returned if no more events can be received by this listener.
     ///
     /// # Examples
     ///
@@ -322,7 +329,7 @@ impl CtrlClose {
     }
 }
 
-/// Creates a new stream which receives "ctrl-shutdown" notifications sent to the
+/// Creates a new listener which receives "ctrl-shutdown" notifications sent to the
 /// process.
 ///
 /// # Examples
@@ -332,10 +339,10 @@ impl CtrlClose {
 ///
 /// #[tokio::main]
 /// async fn main() -> Result<(), Box<dyn std::error::Error>> {
-///     // An infinite stream of CTRL-SHUTDOWN events.
-///     let mut stream = ctrl_shutdown()?;
+///     // A listener of CTRL-SHUTDOWN events.
+///     let mut signal = ctrl_shutdown()?;
 ///
-///     stream.recv().await;
+///     signal.recv().await;
 ///     println!("got CTRL-SHUTDOWN. Cleaning up before exiting");
 ///
 ///     Ok(())
@@ -347,14 +354,14 @@ pub fn ctrl_shutdown() -> io::Result<CtrlShutdown> {
     })
 }
 
-/// Represents a stream which receives "ctrl-shutdown" notitifications sent to the process
+/// Represents a listener which receives "ctrl-shutdown" notitifications sent to the process
 /// via 'SetConsoleCtrlHandler'.
 ///
-/// A notification to this process notifies *all* streams listening for
+/// A notification to this process notifies *all* listeners listening for
 /// this event. Moreover, the notifications **are coalesced** if they aren't processed
 /// quickly enough. This means that if two notifications are received back-to-back,
-/// then the stream may only receive one item about the two notifications.
-#[must_use = "streams do nothing unless polled"]
+/// then the listener may only receive one item about the two notifications.
+#[must_use = "listeners do nothing unless polled"]
 #[derive(Debug)]
 pub struct CtrlShutdown {
     inner: RxFuture,
@@ -363,7 +370,7 @@ pub struct CtrlShutdown {
 impl CtrlShutdown {
     /// Receives the next signal notification event.
     ///
-    /// `None` is returned if no more events can be received by this stream.
+    /// `None` is returned if no more events can be received by this listener.
     ///
     /// # Examples
     ///
@@ -372,11 +379,11 @@ impl CtrlShutdown {
     ///
     /// #[tokio::main]
     /// async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    ///     // An infinite stream of CTRL-SHUTDOWN events.
-    ///     let mut stream = ctrl_shutdown()?;
+    ///     // A listener of CTRL-SHUTDOWN events.
+    ///     let mut signal = ctrl_shutdown()?;
     ///
     ///     // Print whenever a CTRL-SHUTDOWN event is received.
-    ///     stream.recv().await;
+    ///     signal.recv().await;
     ///     println!("got CTRL-SHUTDOWN. Cleaning up before exiting");
     ///
     ///     Ok(())
@@ -389,7 +396,7 @@ impl CtrlShutdown {
     /// Polls to receive the next signal notification event, outside of an
     /// `async` context.
     ///
-    /// `None` is returned if no more events can be received by this stream.
+    /// `None` is returned if no more events can be received by this listener.
     ///
     /// # Examples
     ///
@@ -419,7 +426,7 @@ impl CtrlShutdown {
     }
 }
 
-/// Creates a new stream which receives "ctrl-logoff" notifications sent to the
+/// Creates a new listener which receives "ctrl-logoff" notifications sent to the
 /// process.
 ///
 /// # Examples
@@ -429,10 +436,10 @@ impl CtrlShutdown {
 ///
 /// #[tokio::main]
 /// async fn main() -> Result<(), Box<dyn std::error::Error>> {
-///     // An infinite stream of CTRL-LOGOFF events.
-///     let mut stream = ctrl_logoff()?;
+///     // A listener of CTRL-LOGOFF events.
+///     let mut signal = ctrl_logoff()?;
 ///
-///     stream.recv().await;
+///     signal.recv().await;
 ///     println!("got CTRL-LOGOFF. Cleaning up before exiting");
 ///
 ///     Ok(())
@@ -444,14 +451,14 @@ pub fn ctrl_logoff() -> io::Result<CtrlLogoff> {
     })
 }
 
-/// Represents a stream which receives "ctrl-logoff" notitifications sent to the process
+/// Represents a listener which receives "ctrl-logoff" notitifications sent to the process
 /// via 'SetConsoleCtrlHandler'.
 ///
-/// A notification to this process notifies *all* streams listening for
+/// A notification to this process notifies *all* listeners listening for
 /// this event. Moreover, the notifications **are coalesced** if they aren't processed
 /// quickly enough. This means that if two notifications are received back-to-back,
-/// then the stream may only receive one item about the two notifications.
-#[must_use = "streams do nothing unless polled"]
+/// then the listener may only receive one item about the two notifications.
+#[must_use = "listeners do nothing unless polled"]
 #[derive(Debug)]
 pub struct CtrlLogoff {
     inner: RxFuture,
@@ -460,7 +467,7 @@ pub struct CtrlLogoff {
 impl CtrlLogoff {
     /// Receives the next signal notification event.
     ///
-    /// `None` is returned if no more events can be received by this stream.
+    /// `None` is returned if no more events can be received by this listener.
     ///
     /// # Examples
     ///
@@ -469,11 +476,11 @@ impl CtrlLogoff {
     ///
     /// #[tokio::main]
     /// async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    ///     // An infinite stream of CTRL-LOGOFF events.
-    ///     let mut stream = ctrl_logoff()?;
+    ///     // An listener of CTRL-LOGOFF events.
+    ///     let mut signal = ctrl_logoff()?;
     ///
     ///     // Print whenever a CTRL-LOGOFF event is received.
-    ///     stream.recv().await;
+    ///     signal.recv().await;
     ///     println!("got CTRL-LOGOFF. Cleaning up before exiting");
     ///
     ///     Ok(())
@@ -486,7 +493,7 @@ impl CtrlLogoff {
     /// Polls to receive the next signal notification event, outside of an
     /// `async` context.
     ///
-    /// `None` is returned if no more events can be received by this stream.
+    /// `None` is returned if no more events can be received by this listener.
     ///
     /// # Examples
     ///
diff --git a/tokio/src/sync/batch_semaphore.rs b/tokio/src/sync/batch_semaphore.rs
index 57493f4bd2c..a7885bdf172 100644
--- a/tokio/src/sync/batch_semaphore.rs
+++ b/tokio/src/sync/batch_semaphore.rs
@@ -444,6 +444,7 @@ impl Semaphore {
         }
 
         assert_eq!(acquired, 0);
+        let mut old_waker = None;
 
         // Otherwise, register the waker & enqueue the node.
         node.waker.with_mut(|waker| {
@@ -455,7 +456,7 @@ impl Semaphore {
                 .map(|waker| !waker.will_wake(cx.waker()))
                 .unwrap_or(true)
             {
-                *waker = Some(cx.waker().clone());
+                old_waker = std::mem::replace(waker, Some(cx.waker().clone()));
             }
         });
 
@@ -468,6 +469,8 @@ impl Semaphore {
 
             waiters.queue.push_front(node);
         }
+        drop(waiters);
+        drop(old_waker);
 
         Pending
     }
diff --git a/tokio/src/sync/broadcast.rs b/tokio/src/sync/broadcast.rs
index 452f3b1102b..6e14ef1e1f4 100644
--- a/tokio/src/sync/broadcast.rs
+++ b/tokio/src/sync/broadcast.rs
@@ -4,7 +4,7 @@
 //! A [`Sender`] is used to broadcast values to **all** connected [`Receiver`]
 //! values. [`Sender`] handles are clone-able, allowing concurrent send and
 //! receive actions. [`Sender`] and [`Receiver`] are both `Send` and `Sync` as
-//! long as `T` is also `Send` or `Sync` respectively.
+//! long as `T` is `Send`.
 //!
 //! When a value is sent, **all** [`Receiver`] handles are notified and will
 //! receive the value. The value is stored once inside the channel and cloned on
@@ -18,6 +18,9 @@
 //! returned [`Receiver`] will receive values sent **after** the call to
 //! `subscribe`.
 //!
+//! This channel is also suitable for the single-producer multi-consumer
+//! use-case, where a single sender broadcasts values to many receivers.
+//!
 //! ## Lagging
 //!
 //! As sent messages must be retained until **all** [`Receiver`] handles receive
@@ -51,6 +54,10 @@
 //! all values retained by the channel, the next call to [`recv`] will return
 //! with [`RecvError::Closed`].
 //!
+//! When a [`Receiver`] handle is dropped, any messages not read by the receiver
+//! will be marked as read. If this receiver was the only one not to have read
+//! that message, the message will be dropped at this point.
+//!
 //! [`Sender`]: crate::sync::broadcast::Sender
 //! [`Sender::subscribe`]: crate::sync::broadcast::Sender::subscribe
 //! [`Receiver`]: crate::sync::broadcast::Receiver
@@ -600,6 +607,97 @@ impl<T> Sender<T> {
         new_receiver(shared)
     }
 
+    /// Returns the number of queued values.
+    ///
+    /// A value is queued until it has either been seen by all receivers that were alive at the time
+    /// it was sent, or has been evicted from the queue by subsequent sends that exceeded the
+    /// queue's capacity.
+    ///
+    /// # Note
+    ///
+    /// In contrast to [`Receiver::len`], this method only reports queued values and not values that
+    /// have been evicted from the queue before being seen by all receivers.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use tokio::sync::broadcast;
+    ///
+    /// #[tokio::main]
+    /// async fn main() {
+    ///     let (tx, mut rx1) = broadcast::channel(16);
+    ///     let mut rx2 = tx.subscribe();
+    ///
+    ///     tx.send(10).unwrap();
+    ///     tx.send(20).unwrap();
+    ///     tx.send(30).unwrap();
+    ///
+    ///     assert_eq!(tx.len(), 3);
+    ///
+    ///     rx1.recv().await.unwrap();
+    ///
+    ///     // The len is still 3 since rx2 hasn't seen the first value yet.
+    ///     assert_eq!(tx.len(), 3);
+    ///
+    ///     rx2.recv().await.unwrap();
+    ///
+    ///     assert_eq!(tx.len(), 2);
+    /// }
+    /// ```
+    pub fn len(&self) -> usize {
+        let tail = self.shared.tail.lock();
+
+        let base_idx = (tail.pos & self.shared.mask as u64) as usize;
+        let mut low = 0;
+        let mut high = self.shared.buffer.len();
+        while low < high {
+            let mid = low + (high - low) / 2;
+            let idx = base_idx.wrapping_add(mid) & self.shared.mask;
+            if self.shared.buffer[idx].read().unwrap().rem.load(SeqCst) == 0 {
+                low = mid + 1;
+            } else {
+                high = mid;
+            }
+        }
+
+        self.shared.buffer.len() - low
+    }
+
+    /// Returns true if there are no queued values.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use tokio::sync::broadcast;
+    ///
+    /// #[tokio::main]
+    /// async fn main() {
+    ///     let (tx, mut rx1) = broadcast::channel(16);
+    ///     let mut rx2 = tx.subscribe();
+    ///
+    ///     assert!(tx.is_empty());
+    ///
+    ///     tx.send(10).unwrap();
+    ///
+    ///     assert!(!tx.is_empty());
+    ///
+    ///     rx1.recv().await.unwrap();
+    ///
+    ///     // The queue is still not empty since rx2 hasn't seen the value.
+    ///     assert!(!tx.is_empty());
+    ///
+    ///     rx2.recv().await.unwrap();
+    ///
+    ///     assert!(tx.is_empty());
+    /// }
+    /// ```
+    pub fn is_empty(&self) -> bool {
+        let tail = self.shared.tail.lock();
+
+        let idx = (tail.pos.wrapping_sub(1) & self.shared.mask as u64) as usize;
+        self.shared.buffer[idx].read().unwrap().rem.load(SeqCst) == 0
+    }
+
     /// Returns the number of active receivers
     ///
     /// An active receiver is a [`Receiver`] handle returned from [`channel`] or
@@ -728,7 +826,7 @@ impl<T> Receiver<T> {
     ///     assert_eq!(rx1.len(), 2);
     ///     assert_eq!(rx1.recv().await.unwrap(), 10);
     ///     assert_eq!(rx1.len(), 1);
-    ///     assert_eq!(rx1.recv().await.unwrap(), 20);     
+    ///     assert_eq!(rx1.recv().await.unwrap(), 20);
     ///     assert_eq!(rx1.len(), 0);
     /// }
     /// ```
@@ -758,7 +856,7 @@ impl<T> Receiver<T> {
     ///
     ///     assert!(!rx1.is_empty());
     ///     assert_eq!(rx1.recv().await.unwrap(), 10);
-    ///     assert_eq!(rx1.recv().await.unwrap(), 20);     
+    ///     assert_eq!(rx1.recv().await.unwrap(), 20);
     ///     assert!(rx1.is_empty());
     /// }
     /// ```
diff --git a/tokio/src/sync/mod.rs b/tokio/src/sync/mod.rs
index 457e6ab2946..70fd9b9e32d 100644
--- a/tokio/src/sync/mod.rs
+++ b/tokio/src/sync/mod.rs
@@ -94,6 +94,10 @@
 //! producers to a single consumer. This channel is often used to send work to a
 //! task or to receive the result of many computations.
 //!
+//! This is also the channel you should use if you want to send many messages
+//! from a single producer to a single consumer. There is no dedicated spsc
+//! channel.
+//!
 //! **Example:** using an mpsc to incrementally stream the results of a series
 //! of computations.
 //!
@@ -244,6 +248,10 @@
 //! This channel tends to be used less often than `oneshot` and `mpsc` but still
 //! has its use cases.
 //!
+//! This is also the channel you should use if you want to broadcast values from
+//! a single producer to many consumers. There is no dedicated spmc broadcast
+//! channel.
+//!
 //! Basic usage
 //!
 //! ```
@@ -441,7 +449,7 @@ cfg_sync! {
     pub mod mpsc;
 
     mod mutex;
-    pub use mutex::{Mutex, MutexGuard, TryLockError, OwnedMutexGuard, MappedMutexGuard};
+    pub use mutex::{Mutex, MutexGuard, TryLockError, OwnedMutexGuard, MappedMutexGuard, OwnedMappedMutexGuard};
 
     pub(crate) mod notify;
     pub use notify::Notify;
diff --git a/tokio/src/sync/mpsc/block.rs b/tokio/src/sync/mpsc/block.rs
index 58f4a9f6cc3..39c3e1be2d9 100644
--- a/tokio/src/sync/mpsc/block.rs
+++ b/tokio/src/sync/mpsc/block.rs
@@ -1,6 +1,7 @@
 use crate::loom::cell::UnsafeCell;
 use crate::loom::sync::atomic::{AtomicPtr, AtomicUsize};
 
+use std::alloc::Layout;
 use std::mem::MaybeUninit;
 use std::ops;
 use std::ptr::{self, NonNull};
@@ -10,6 +11,17 @@ use std::sync::atomic::Ordering::{self, AcqRel, Acquire, Release};
 ///
 /// Each block in the list can hold up to `BLOCK_CAP` messages.
 pub(crate) struct Block<T> {
+    /// The header fields.
+    header: BlockHeader<T>,
+
+    /// Array containing values pushed into the block. Values are stored in a
+    /// continuous array in order to improve cache line behavior when reading.
+    /// The values must be manually dropped.
+    values: Values<T>,
+}
+
+/// Extra fields for a `Block<T>`.
+struct BlockHeader<T> {
     /// The start index of this block.
     ///
     /// Slots in this block have indices in `start_index .. start_index + BLOCK_CAP`.
@@ -24,11 +36,6 @@ pub(crate) struct Block<T> {
     /// The observed `tail_position` value *after* the block has been passed by
     /// `block_tail`.
     observed_tail_position: UnsafeCell<usize>,
-
-    /// Array containing values pushed into the block. Values are stored in a
-    /// continuous array in order to improve cache line behavior when reading.
-    /// The values must be manually dropped.
-    values: Values<T>,
 }
 
 pub(crate) enum Read<T> {
@@ -36,6 +43,7 @@ pub(crate) enum Read<T> {
     Closed,
 }
 
+#[repr(transparent)]
 struct Values<T>([UnsafeCell<MaybeUninit<T>>; BLOCK_CAP]);
 
 use super::BLOCK_CAP;
@@ -71,28 +79,56 @@ pub(crate) fn offset(slot_index: usize) -> usize {
     SLOT_MASK & slot_index
 }
 
+generate_addr_of_methods! {
+    impl<T> Block<T> {
+        unsafe fn addr_of_header(self: NonNull<Self>) -> NonNull<BlockHeader<T>> {
+            &self.header
+        }
+
+        unsafe fn addr_of_values(self: NonNull<Self>) -> NonNull<Values<T>> {
+            &self.values
+        }
+    }
+}
+
 impl<T> Block<T> {
-    pub(crate) fn new(start_index: usize) -> Block<T> {
-        Block {
-            // The absolute index in the channel of the first slot in the block.
-            start_index,
+    pub(crate) fn new(start_index: usize) -> Box<Block<T>> {
+        unsafe {
+            // Allocate the block on the heap.
+            // SAFETY: The size of the Block<T> is non-zero, since it is at least the size of the header.
+            let block = std::alloc::alloc(Layout::new::<Block<T>>()) as *mut Block<T>;
+            let block = match NonNull::new(block) {
+                Some(block) => block,
+                None => std::alloc::handle_alloc_error(Layout::new::<Block<T>>()),
+            };
+
+            // Write the header to the block.
+            Block::addr_of_header(block).as_ptr().write(BlockHeader {
+                // The absolute index in the channel of the first slot in the block.
+                start_index,
 
-            // Pointer to the next block in the linked list.
-            next: AtomicPtr::new(ptr::null_mut()),
+                // Pointer to the next block in the linked list.
+                next: AtomicPtr::new(ptr::null_mut()),
 
-            ready_slots: AtomicUsize::new(0),
+                ready_slots: AtomicUsize::new(0),
 
-            observed_tail_position: UnsafeCell::new(0),
+                observed_tail_position: UnsafeCell::new(0),
+            });
 
-            // Value storage
-            values: unsafe { Values::uninitialized() },
+            // Initialize the values array.
+            Values::initialize(Block::addr_of_values(block));
+
+            // Convert the pointer to a `Box`.
+            // Safety: The raw pointer was allocated using the global allocator, and with
+            // the layout for a `Block<T>`, so it's valid to convert it to box.
+            Box::from_raw(block.as_ptr())
         }
     }
 
     /// Returns `true` if the block matches the given index.
     pub(crate) fn is_at_index(&self, index: usize) -> bool {
         debug_assert!(offset(index) == 0);
-        self.start_index == index
+        self.header.start_index == index
     }
 
     /// Returns the number of blocks between `self` and the block at the
@@ -101,7 +137,7 @@ impl<T> Block<T> {
     /// `start_index` must represent a block *after* `self`.
     pub(crate) fn distance(&self, other_index: usize) -> usize {
         debug_assert!(offset(other_index) == 0);
-        other_index.wrapping_sub(self.start_index) / BLOCK_CAP
+        other_index.wrapping_sub(self.header.start_index) / BLOCK_CAP
     }
 
     /// Reads the value at the given offset.
@@ -116,7 +152,7 @@ impl<T> Block<T> {
     pub(crate) unsafe fn read(&self, slot_index: usize) -> Option<Read<T>> {
         let offset = offset(slot_index);
 
-        let ready_bits = self.ready_slots.load(Acquire);
+        let ready_bits = self.header.ready_slots.load(Acquire);
 
         if !is_ready(ready_bits, offset) {
             if is_tx_closed(ready_bits) {
@@ -156,7 +192,7 @@ impl<T> Block<T> {
 
     /// Signal to the receiver that the sender half of the list is closed.
     pub(crate) unsafe fn tx_close(&self) {
-        self.ready_slots.fetch_or(TX_CLOSED, Release);
+        self.header.ready_slots.fetch_or(TX_CLOSED, Release);
     }
 
     /// Resets the block to a blank state. This enables reusing blocks in the
@@ -169,9 +205,9 @@ impl<T> Block<T> {
     /// * All slots are empty.
     /// * The caller holds a unique pointer to the block.
     pub(crate) unsafe fn reclaim(&mut self) {
-        self.start_index = 0;
-        self.next = AtomicPtr::new(ptr::null_mut());
-        self.ready_slots = AtomicUsize::new(0);
+        self.header.start_index = 0;
+        self.header.next = AtomicPtr::new(ptr::null_mut());
+        self.header.ready_slots = AtomicUsize::new(0);
     }
 
     /// Releases the block to the rx half for freeing.
@@ -187,19 +223,20 @@ impl<T> Block<T> {
     pub(crate) unsafe fn tx_release(&self, tail_position: usize) {
         // Track the observed tail_position. Any sender targeting a greater
         // tail_position is guaranteed to not access this block.
-        self.observed_tail_position
+        self.header
+            .observed_tail_position
             .with_mut(|ptr| *ptr = tail_position);
 
         // Set the released bit, signalling to the receiver that it is safe to
         // free the block's memory as soon as all slots **prior** to
         // `observed_tail_position` have been filled.
-        self.ready_slots.fetch_or(RELEASED, Release);
+        self.header.ready_slots.fetch_or(RELEASED, Release);
     }
 
     /// Mark a slot as ready
     fn set_ready(&self, slot: usize) {
         let mask = 1 << slot;
-        self.ready_slots.fetch_or(mask, Release);
+        self.header.ready_slots.fetch_or(mask, Release);
     }
 
     /// Returns `true` when all slots have their `ready` bits set.
@@ -214,25 +251,31 @@ impl<T> Block<T> {
     /// single atomic cell. However, this could have negative impact on cache
     /// behavior as there would be many more mutations to a single slot.
     pub(crate) fn is_final(&self) -> bool {
-        self.ready_slots.load(Acquire) & READY_MASK == READY_MASK
+        self.header.ready_slots.load(Acquire) & READY_MASK == READY_MASK
     }
 
     /// Returns the `observed_tail_position` value, if set
     pub(crate) fn observed_tail_position(&self) -> Option<usize> {
-        if 0 == RELEASED & self.ready_slots.load(Acquire) {
+        if 0 == RELEASED & self.header.ready_slots.load(Acquire) {
             None
         } else {
-            Some(self.observed_tail_position.with(|ptr| unsafe { *ptr }))
+            Some(
+                self.header
+                    .observed_tail_position
+                    .with(|ptr| unsafe { *ptr }),
+            )
         }
     }
 
     /// Loads the next block
     pub(crate) fn load_next(&self, ordering: Ordering) -> Option<NonNull<Block<T>>> {
-        let ret = NonNull::new(self.next.load(ordering));
+        let ret = NonNull::new(self.header.next.load(ordering));
 
         debug_assert!(unsafe {
-            ret.map(|block| block.as_ref().start_index == self.start_index.wrapping_add(BLOCK_CAP))
-                .unwrap_or(true)
+            ret.map(|block| {
+                block.as_ref().header.start_index == self.header.start_index.wrapping_add(BLOCK_CAP)
+            })
+            .unwrap_or(true)
         });
 
         ret
@@ -260,9 +303,10 @@ impl<T> Block<T> {
         success: Ordering,
         failure: Ordering,
     ) -> Result<(), NonNull<Block<T>>> {
-        block.as_mut().start_index = self.start_index.wrapping_add(BLOCK_CAP);
+        block.as_mut().header.start_index = self.header.start_index.wrapping_add(BLOCK_CAP);
 
         let next_ptr = self
+            .header
             .next
             .compare_exchange(ptr::null_mut(), block.as_ptr(), success, failure)
             .unwrap_or_else(|x| x);
@@ -291,7 +335,7 @@ impl<T> Block<T> {
         // Create the new block. It is assumed that the block will become the
         // next one after `&self`. If this turns out to not be the case,
         // `start_index` is updated accordingly.
-        let new_block = Box::new(Block::new(self.start_index + BLOCK_CAP));
+        let new_block = Block::new(self.header.start_index + BLOCK_CAP);
 
         let mut new_block = unsafe { NonNull::new_unchecked(Box::into_raw(new_block)) };
 
@@ -308,7 +352,8 @@ impl<T> Block<T> {
         // `Release` ensures that the newly allocated block is available to
         // other threads acquiring the next pointer.
         let next = NonNull::new(
-            self.next
+            self.header
+                .next
                 .compare_exchange(ptr::null_mut(), new_block.as_ptr(), AcqRel, Acquire)
                 .unwrap_or_else(|x| x),
         );
@@ -360,19 +405,20 @@ fn is_tx_closed(bits: usize) -> bool {
 }
 
 impl<T> Values<T> {
-    unsafe fn uninitialized() -> Values<T> {
-        let mut vals = MaybeUninit::uninit();
-
+    /// Initialize a `Values` struct from a pointer.
+    ///
+    /// # Safety
+    ///
+    /// The raw pointer must be valid for writing a `Values<T>`.
+    unsafe fn initialize(_value: NonNull<Values<T>>) {
         // When fuzzing, `UnsafeCell` needs to be initialized.
         if_loom! {
-            let p = vals.as_mut_ptr() as *mut UnsafeCell<MaybeUninit<T>>;
+            let p = _value.as_ptr() as *mut UnsafeCell<MaybeUninit<T>>;
             for i in 0..BLOCK_CAP {
                 p.add(i)
                     .write(UnsafeCell::new(MaybeUninit::uninit()));
             }
         }
-
-        Values(vals.assume_init())
     }
 }
 
@@ -383,3 +429,20 @@ impl<T> ops::Index<usize> for Values<T> {
         self.0.index(index)
     }
 }
+
+#[cfg(all(test, not(loom)))]
+#[test]
+fn assert_no_stack_overflow() {
+    // https://github.com/tokio-rs/tokio/issues/5293
+
+    struct Foo {
+        _a: [u8; 2_000_000],
+    }
+
+    assert_eq!(
+        Layout::new::<MaybeUninit<Block<Foo>>>(),
+        Layout::new::<Block<Foo>>()
+    );
+
+    let _block = Block::<Foo>::new(0);
+}
diff --git a/tokio/src/sync/mpsc/bounded.rs b/tokio/src/sync/mpsc/bounded.rs
index 8babdc7e076..30bad6aa8e8 100644
--- a/tokio/src/sync/mpsc/bounded.rs
+++ b/tokio/src/sync/mpsc/bounded.rs
@@ -326,6 +326,7 @@ impl<T> Receiver<T> {
     /// ```
     #[track_caller]
     #[cfg(feature = "sync")]
+    #[cfg_attr(docsrs, doc(alias = "recv_blocking"))]
     pub fn blocking_recv(&mut self) -> Option<T> {
         crate::future::block_on(self.recv())
     }
@@ -696,6 +697,7 @@ impl<T> Sender<T> {
     /// ```
     #[track_caller]
     #[cfg(feature = "sync")]
+    #[cfg_attr(docsrs, doc(alias = "send_blocking"))]
     pub fn blocking_send(&self, value: T) -> Result<(), SendError<T>> {
         crate::future::block_on(self.send(value))
     }
diff --git a/tokio/src/sync/mpsc/list.rs b/tokio/src/sync/mpsc/list.rs
index e4eeb454118..10b29575bdb 100644
--- a/tokio/src/sync/mpsc/list.rs
+++ b/tokio/src/sync/mpsc/list.rs
@@ -44,7 +44,7 @@ pub(crate) enum TryPopResult<T> {
 
 pub(crate) fn channel<T>() -> (Tx<T>, Rx<T>) {
     // Create the initial block shared between the tx and rx halves.
-    let initial_block = Box::new(Block::new(0));
+    let initial_block = Block::new(0);
     let initial_block_ptr = Box::into_raw(initial_block);
 
     let tx = Tx {
diff --git a/tokio/src/sync/mpsc/mod.rs b/tokio/src/sync/mpsc/mod.rs
index fff309127ad..b2af084b2ae 100644
--- a/tokio/src/sync/mpsc/mod.rs
+++ b/tokio/src/sync/mpsc/mod.rs
@@ -21,6 +21,9 @@
 //! when additional capacity is available. In other words, the channel provides
 //! backpressure.
 //!
+//! This channel is also suitable for the single-producer single-consumer
+//! use-case. (Unless you only need to send one message, in which case you
+//! should use the [oneshot] channel.)
 //!
 //! # Disconnection
 //!
@@ -30,7 +33,8 @@
 //!
 //! If the [`Receiver`] handle is dropped, then messages can no longer
 //! be read out of the channel. In this case, all further attempts to send will
-//! result in an error.
+//! result in an error. Additionally, all unread messages will be drained from the
+//! channel and dropped.
 //!
 //! # Clean Shutdown
 //!
@@ -62,7 +66,7 @@
 //! in mind, but they can also be generalized to other kinds of channels. In
 //! general, any channel method that isn't marked async can be called anywhere,
 //! including outside of the runtime. For example, sending a message on a
-//! oneshot channel from outside the runtime is perfectly fine.
+//! [oneshot] channel from outside the runtime is perfectly fine.
 //!
 //! # Multiple runtimes
 //!
@@ -82,6 +86,7 @@
 //! [blocking-recv]: crate::sync::mpsc::Receiver::blocking_recv()
 //! [`UnboundedSender`]: crate::sync::mpsc::UnboundedSender
 //! [`UnboundedReceiver`]: crate::sync::mpsc::UnboundedReceiver
+//! [oneshot]: crate::sync::oneshot
 //! [`Handle::block_on`]: crate::runtime::Handle::block_on()
 //! [std-unbounded]: std::sync::mpsc::channel
 //! [crossbeam-unbounded]: https://docs.rs/crossbeam/*/crossbeam/channel/fn.unbounded.html
diff --git a/tokio/src/sync/mpsc/unbounded.rs b/tokio/src/sync/mpsc/unbounded.rs
index 501020433cf..cd83fc12513 100644
--- a/tokio/src/sync/mpsc/unbounded.rs
+++ b/tokio/src/sync/mpsc/unbounded.rs
@@ -243,6 +243,7 @@ impl<T> UnboundedReceiver<T> {
     /// ```
     #[track_caller]
     #[cfg(feature = "sync")]
+    #[cfg_attr(docsrs, doc(alias = "recv_blocking"))]
     pub fn blocking_recv(&mut self) -> Option<T> {
         crate::future::block_on(self.recv())
     }
diff --git a/tokio/src/sync/mutex.rs b/tokio/src/sync/mutex.rs
index 024755c83b5..a378116f857 100644
--- a/tokio/src/sync/mutex.rs
+++ b/tokio/src/sync/mutex.rs
@@ -6,9 +6,10 @@ use crate::util::trace;
 
 use std::cell::UnsafeCell;
 use std::error::Error;
+use std::marker::PhantomData;
 use std::ops::{Deref, DerefMut};
 use std::sync::Arc;
-use std::{fmt, marker, mem};
+use std::{fmt, mem, ptr};
 
 /// An asynchronous `Mutex`-like type.
 ///
@@ -141,8 +142,11 @@ pub struct Mutex<T: ?Sized> {
 ///
 /// The lock is automatically released whenever the guard is dropped, at which
 /// point `lock` will succeed yet again.
+#[clippy::has_significant_drop]
 #[must_use = "if unused the Mutex will immediately unlock"]
 pub struct MutexGuard<'a, T: ?Sized> {
+    // When changing the fields in this struct, make sure to update the
+    // `skip_drop` method.
     #[cfg(all(tokio_unstable, feature = "tracing"))]
     resource_span: tracing::Span,
     lock: &'a Mutex<T>,
@@ -163,7 +167,10 @@ pub struct MutexGuard<'a, T: ?Sized> {
 /// point `lock` will succeed yet again.
 ///
 /// [`Arc`]: std::sync::Arc
+#[clippy::has_significant_drop]
 pub struct OwnedMutexGuard<T: ?Sized> {
+    // When changing the fields in this struct, make sure to update the
+    // `skip_drop` method.
     #[cfg(all(tokio_unstable, feature = "tracing"))]
     resource_span: tracing::Span,
     lock: Arc<Mutex<T>>,
@@ -174,12 +181,71 @@ pub struct OwnedMutexGuard<T: ?Sized> {
 /// This can be used to hold a subfield of the protected data.
 ///
 /// [`MutexGuard::map`]: method@MutexGuard::map
+#[clippy::has_significant_drop]
 #[must_use = "if unused the Mutex will immediately unlock"]
 pub struct MappedMutexGuard<'a, T: ?Sized> {
+    // When changing the fields in this struct, make sure to update the
+    // `skip_drop` method.
+    #[cfg(all(tokio_unstable, feature = "tracing"))]
+    resource_span: tracing::Span,
     s: &'a semaphore::Semaphore,
     data: *mut T,
     // Needed to tell the borrow checker that we are holding a `&mut T`
-    marker: marker::PhantomData<&'a mut T>,
+    marker: PhantomData<&'a mut T>,
+}
+
+/// A owned handle to a held `Mutex` that has had a function applied to it via
+/// [`OwnedMutexGuard::map`].
+///
+/// This can be used to hold a subfield of the protected data.
+///
+/// [`OwnedMutexGuard::map`]: method@OwnedMutexGuard::map
+#[clippy::has_significant_drop]
+#[must_use = "if unused the Mutex will immediately unlock"]
+pub struct OwnedMappedMutexGuard<T: ?Sized, U: ?Sized = T> {
+    // When changing the fields in this struct, make sure to update the
+    // `skip_drop` method.
+    #[cfg(all(tokio_unstable, feature = "tracing"))]
+    resource_span: tracing::Span,
+    data: *mut U,
+    lock: Arc<Mutex<T>>,
+}
+
+/// A helper type used when taking apart a `MutexGuard` without running its
+/// Drop implementation.
+#[allow(dead_code)] // Unused fields are still used in Drop.
+struct MutexGuardInner<'a, T: ?Sized> {
+    #[cfg(all(tokio_unstable, feature = "tracing"))]
+    resource_span: tracing::Span,
+    lock: &'a Mutex<T>,
+}
+
+/// A helper type used when taking apart a `OwnedMutexGuard` without running
+/// its Drop implementation.
+struct OwnedMutexGuardInner<T: ?Sized> {
+    #[cfg(all(tokio_unstable, feature = "tracing"))]
+    resource_span: tracing::Span,
+    lock: Arc<Mutex<T>>,
+}
+
+/// A helper type used when taking apart a `MappedMutexGuard` without running
+/// its Drop implementation.
+#[allow(dead_code)] // Unused fields are still used in Drop.
+struct MappedMutexGuardInner<'a, T: ?Sized> {
+    #[cfg(all(tokio_unstable, feature = "tracing"))]
+    resource_span: tracing::Span,
+    s: &'a semaphore::Semaphore,
+    data: *mut T,
+}
+
+/// A helper type used when taking apart a `OwnedMappedMutexGuard` without running
+/// its Drop implementation.
+#[allow(dead_code)] // Unused fields are still used in Drop.
+struct OwnedMappedMutexGuardInner<T: ?Sized, U: ?Sized> {
+    #[cfg(all(tokio_unstable, feature = "tracing"))]
+    resource_span: tracing::Span,
+    data: *mut U,
+    lock: Arc<Mutex<T>>,
 }
 
 // As long as T: Send, it's fine to send and share Mutex<T> between threads.
@@ -192,6 +258,19 @@ unsafe impl<T> Sync for OwnedMutexGuard<T> where T: ?Sized + Send + Sync {}
 unsafe impl<'a, T> Sync for MappedMutexGuard<'a, T> where T: ?Sized + Sync + 'a {}
 unsafe impl<'a, T> Send for MappedMutexGuard<'a, T> where T: ?Sized + Send + 'a {}
 
+unsafe impl<T, U> Sync for OwnedMappedMutexGuard<T, U>
+where
+    T: ?Sized + Send + Sync,
+    U: ?Sized + Send + Sync,
+{
+}
+unsafe impl<T, U> Send for OwnedMappedMutexGuard<T, U>
+where
+    T: ?Sized + Send,
+    U: ?Sized + Send,
+{
+}
+
 /// Error returned from the [`Mutex::try_lock`], [`RwLock::try_read`] and
 /// [`RwLock::try_write`] functions.
 ///
@@ -337,15 +416,27 @@ impl<T: ?Sized> Mutex<T> {
     /// }
     /// ```
     pub async fn lock(&self) -> MutexGuard<'_, T> {
+        let acquire_fut = async {
+            self.acquire().await;
+
+            MutexGuard {
+                lock: self,
+                #[cfg(all(tokio_unstable, feature = "tracing"))]
+                resource_span: self.resource_span.clone(),
+            }
+        };
+
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        trace::async_op(
-            || self.acquire(),
+        let acquire_fut = trace::async_op(
+            move || acquire_fut,
             self.resource_span.clone(),
             "Mutex::lock",
             "poll",
             false,
-        )
-        .await;
+        );
+
+        #[allow(clippy::let_and_return)] // this lint triggers when disabling tracing
+        let guard = acquire_fut.await;
 
         #[cfg(all(tokio_unstable, feature = "tracing"))]
         self.resource_span.in_scope(|| {
@@ -355,14 +446,7 @@ impl<T: ?Sized> Mutex<T> {
             );
         });
 
-        #[cfg(any(not(tokio_unstable), not(feature = "tracing")))]
-        self.acquire().await;
-
-        MutexGuard {
-            lock: self,
-            #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span: self.resource_span.clone(),
-        }
+        guard
     }
 
     /// Blockingly locks this `Mutex`. When the lock has been acquired, function returns a
@@ -414,6 +498,7 @@ impl<T: ?Sized> Mutex<T> {
     /// ```
     #[track_caller]
     #[cfg(feature = "sync")]
+    #[cfg_attr(docsrs, doc(alias = "lock_blocking"))]
     pub fn blocking_lock(&self) -> MutexGuard<'_, T> {
         crate::future::block_on(self.lock())
     }
@@ -508,34 +593,39 @@ impl<T: ?Sized> Mutex<T> {
     /// [`Arc`]: std::sync::Arc
     pub async fn lock_owned(self: Arc<Self>) -> OwnedMutexGuard<T> {
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        trace::async_op(
-            || self.acquire(),
-            self.resource_span.clone(),
+        let resource_span = self.resource_span.clone();
+
+        let acquire_fut = async {
+            self.acquire().await;
+
+            OwnedMutexGuard {
+                #[cfg(all(tokio_unstable, feature = "tracing"))]
+                resource_span: self.resource_span.clone(),
+                lock: self,
+            }
+        };
+
+        #[cfg(all(tokio_unstable, feature = "tracing"))]
+        let acquire_fut = trace::async_op(
+            move || acquire_fut,
+            resource_span,
             "Mutex::lock_owned",
             "poll",
             false,
-        )
-        .await;
+        );
+
+        #[allow(clippy::let_and_return)] // this lint triggers when disabling tracing
+        let guard = acquire_fut.await;
 
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        self.resource_span.in_scope(|| {
+        guard.resource_span.in_scope(|| {
             tracing::trace!(
                 target: "runtime::resource::state_update",
                 locked = true,
             );
         });
 
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = self.resource_span.clone();
-
-        #[cfg(any(not(tokio_unstable), not(feature = "tracing")))]
-        self.acquire().await;
-
-        OwnedMutexGuard {
-            lock: self,
-            #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
-        }
+        guard
     }
 
     async fn acquire(&self) {
@@ -566,6 +656,12 @@ impl<T: ?Sized> Mutex<T> {
     pub fn try_lock(&self) -> Result<MutexGuard<'_, T>, TryLockError> {
         match self.s.try_acquire(1) {
             Ok(_) => {
+                let guard = MutexGuard {
+                    lock: self,
+                    #[cfg(all(tokio_unstable, feature = "tracing"))]
+                    resource_span: self.resource_span.clone(),
+                };
+
                 #[cfg(all(tokio_unstable, feature = "tracing"))]
                 self.resource_span.in_scope(|| {
                     tracing::trace!(
@@ -574,11 +670,7 @@ impl<T: ?Sized> Mutex<T> {
                     );
                 });
 
-                Ok(MutexGuard {
-                    lock: self,
-                    #[cfg(all(tokio_unstable, feature = "tracing"))]
-                    resource_span: self.resource_span.clone(),
-                })
+                Ok(guard)
             }
             Err(_) => Err(TryLockError(())),
         }
@@ -635,22 +727,21 @@ impl<T: ?Sized> Mutex<T> {
     pub fn try_lock_owned(self: Arc<Self>) -> Result<OwnedMutexGuard<T>, TryLockError> {
         match self.s.try_acquire(1) {
             Ok(_) => {
+                let guard = OwnedMutexGuard {
+                    #[cfg(all(tokio_unstable, feature = "tracing"))]
+                    resource_span: self.resource_span.clone(),
+                    lock: self,
+                };
+
                 #[cfg(all(tokio_unstable, feature = "tracing"))]
-                self.resource_span.in_scope(|| {
+                guard.resource_span.in_scope(|| {
                     tracing::trace!(
                         target: "runtime::resource::state_update",
                         locked = true,
                     );
                 });
 
-                #[cfg(all(tokio_unstable, feature = "tracing"))]
-                let resource_span = self.resource_span.clone();
-
-                Ok(OwnedMutexGuard {
-                    lock: self,
-                    #[cfg(all(tokio_unstable, feature = "tracing"))]
-                    resource_span,
-                })
+                Ok(guard)
             }
             Err(_) => Err(TryLockError(())),
         }
@@ -710,6 +801,17 @@ where
 // === impl MutexGuard ===
 
 impl<'a, T: ?Sized> MutexGuard<'a, T> {
+    fn skip_drop(self) -> MutexGuardInner<'a, T> {
+        let me = mem::ManuallyDrop::new(self);
+        // SAFETY: This duplicates the `resource_span` and then forgets the
+        // original. In the end, we have not duplicated or forgotten any values.
+        MutexGuardInner {
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: unsafe { std::ptr::read(&me.resource_span) },
+            lock: me.lock,
+        }
+    }
+
     /// Makes a new [`MappedMutexGuard`] for a component of the locked data.
     ///
     /// This operation cannot fail as the [`MutexGuard`] passed in already locked the mutex.
@@ -746,12 +848,13 @@ impl<'a, T: ?Sized> MutexGuard<'a, T> {
         F: FnOnce(&mut T) -> &mut U,
     {
         let data = f(&mut *this) as *mut U;
-        let s = &this.lock.s;
-        mem::forget(this);
+        let inner = this.skip_drop();
         MappedMutexGuard {
-            s,
+            s: &inner.lock.s,
             data,
-            marker: marker::PhantomData,
+            marker: PhantomData,
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: inner.resource_span,
         }
     }
 
@@ -796,12 +899,13 @@ impl<'a, T: ?Sized> MutexGuard<'a, T> {
             Some(data) => data as *mut U,
             None => return Err(this),
         };
-        let s = &this.lock.s;
-        mem::forget(this);
+        let inner = this.skip_drop();
         Ok(MappedMutexGuard {
-            s,
+            s: &inner.lock.s,
             data,
-            marker: marker::PhantomData,
+            marker: PhantomData,
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: inner.resource_span,
         })
     }
 
@@ -834,6 +938,8 @@ impl<'a, T: ?Sized> MutexGuard<'a, T> {
 
 impl<T: ?Sized> Drop for MutexGuard<'_, T> {
     fn drop(&mut self) {
+        self.lock.s.release(1);
+
         #[cfg(all(tokio_unstable, feature = "tracing"))]
         self.resource_span.in_scope(|| {
             tracing::trace!(
@@ -841,7 +947,6 @@ impl<T: ?Sized> Drop for MutexGuard<'_, T> {
                 locked = false,
             );
         });
-        self.lock.s.release(1);
     }
 }
 
@@ -873,6 +978,116 @@ impl<T: ?Sized + fmt::Display> fmt::Display for MutexGuard<'_, T> {
 // === impl OwnedMutexGuard ===
 
 impl<T: ?Sized> OwnedMutexGuard<T> {
+    fn skip_drop(self) -> OwnedMutexGuardInner<T> {
+        let me = mem::ManuallyDrop::new(self);
+        // SAFETY: This duplicates the values in every field of the guard, then
+        // forgets the originals, so in the end no value is duplicated.
+        unsafe {
+            OwnedMutexGuardInner {
+                lock: ptr::read(&me.lock),
+                #[cfg(all(tokio_unstable, feature = "tracing"))]
+                resource_span: ptr::read(&me.resource_span),
+            }
+        }
+    }
+
+    /// Makes a new [`OwnedMappedMutexGuard`] for a component of the locked data.
+    ///
+    /// This operation cannot fail as the [`OwnedMutexGuard`] passed in already locked the mutex.
+    ///
+    /// This is an associated function that needs to be used as `OwnedMutexGuard::map(...)`. A method
+    /// would interfere with methods of the same name on the contents of the locked data.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use tokio::sync::{Mutex, OwnedMutexGuard};
+    /// use std::sync::Arc;
+    ///
+    /// #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+    /// struct Foo(u32);
+    ///
+    /// # #[tokio::main]
+    /// # async fn main() {
+    /// let foo = Arc::new(Mutex::new(Foo(1)));
+    ///
+    /// {
+    ///     let mut mapped = OwnedMutexGuard::map(foo.clone().lock_owned().await, |f| &mut f.0);
+    ///     *mapped = 2;
+    /// }
+    ///
+    /// assert_eq!(Foo(2), *foo.lock().await);
+    /// # }
+    /// ```
+    ///
+    /// [`OwnedMutexGuard`]: struct@OwnedMutexGuard
+    /// [`OwnedMappedMutexGuard`]: struct@OwnedMappedMutexGuard
+    #[inline]
+    pub fn map<U, F>(mut this: Self, f: F) -> OwnedMappedMutexGuard<T, U>
+    where
+        F: FnOnce(&mut T) -> &mut U,
+    {
+        let data = f(&mut *this) as *mut U;
+        let inner = this.skip_drop();
+        OwnedMappedMutexGuard {
+            data,
+            lock: inner.lock,
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: inner.resource_span,
+        }
+    }
+
+    /// Attempts to make a new [`OwnedMappedMutexGuard`] for a component of the locked data. The
+    /// original guard is returned if the closure returns `None`.
+    ///
+    /// This operation cannot fail as the [`OwnedMutexGuard`] passed in already locked the mutex.
+    ///
+    /// This is an associated function that needs to be used as `OwnedMutexGuard::try_map(...)`. A
+    /// method would interfere with methods of the same name on the contents of the locked data.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use tokio::sync::{Mutex, OwnedMutexGuard};
+    /// use std::sync::Arc;
+    ///
+    /// #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+    /// struct Foo(u32);
+    ///
+    /// # #[tokio::main]
+    /// # async fn main() {
+    /// let foo = Arc::new(Mutex::new(Foo(1)));
+    ///
+    /// {
+    ///     let mut mapped = OwnedMutexGuard::try_map(foo.clone().lock_owned().await, |f| Some(&mut f.0))
+    ///         .expect("should not fail");
+    ///     *mapped = 2;
+    /// }
+    ///
+    /// assert_eq!(Foo(2), *foo.lock().await);
+    /// # }
+    /// ```
+    ///
+    /// [`OwnedMutexGuard`]: struct@OwnedMutexGuard
+    /// [`OwnedMappedMutexGuard`]: struct@OwnedMappedMutexGuard
+    #[inline]
+    pub fn try_map<U, F>(mut this: Self, f: F) -> Result<OwnedMappedMutexGuard<T, U>, Self>
+    where
+        F: FnOnce(&mut T) -> Option<&mut U>,
+    {
+        let data = match f(&mut *this) {
+            Some(data) => data as *mut U,
+            None => return Err(this),
+        };
+        let inner = this.skip_drop();
+        Ok(OwnedMappedMutexGuard {
+            data,
+            lock: inner.lock,
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: inner.resource_span,
+        })
+    }
+
     /// Returns a reference to the original `Arc<Mutex>`.
     ///
     /// ```
@@ -903,6 +1118,8 @@ impl<T: ?Sized> OwnedMutexGuard<T> {
 
 impl<T: ?Sized> Drop for OwnedMutexGuard<T> {
     fn drop(&mut self) {
+        self.lock.s.release(1);
+
         #[cfg(all(tokio_unstable, feature = "tracing"))]
         self.resource_span.in_scope(|| {
             tracing::trace!(
@@ -910,7 +1127,6 @@ impl<T: ?Sized> Drop for OwnedMutexGuard<T> {
                 locked = false,
             );
         });
-        self.lock.s.release(1)
     }
 }
 
@@ -942,6 +1158,16 @@ impl<T: ?Sized + fmt::Display> fmt::Display for OwnedMutexGuard<T> {
 // === impl MappedMutexGuard ===
 
 impl<'a, T: ?Sized> MappedMutexGuard<'a, T> {
+    fn skip_drop(self) -> MappedMutexGuardInner<'a, T> {
+        let me = mem::ManuallyDrop::new(self);
+        MappedMutexGuardInner {
+            s: me.s,
+            data: me.data,
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: unsafe { std::ptr::read(&me.resource_span) },
+        }
+    }
+
     /// Makes a new [`MappedMutexGuard`] for a component of the locked data.
     ///
     /// This operation cannot fail as the [`MappedMutexGuard`] passed in already locked the mutex.
@@ -956,12 +1182,13 @@ impl<'a, T: ?Sized> MappedMutexGuard<'a, T> {
         F: FnOnce(&mut T) -> &mut U,
     {
         let data = f(&mut *this) as *mut U;
-        let s = this.s;
-        mem::forget(this);
+        let inner = this.skip_drop();
         MappedMutexGuard {
-            s,
+            s: inner.s,
             data,
-            marker: marker::PhantomData,
+            marker: PhantomData,
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: inner.resource_span,
         }
     }
 
@@ -983,19 +1210,28 @@ impl<'a, T: ?Sized> MappedMutexGuard<'a, T> {
             Some(data) => data as *mut U,
             None => return Err(this),
         };
-        let s = this.s;
-        mem::forget(this);
+        let inner = this.skip_drop();
         Ok(MappedMutexGuard {
-            s,
+            s: inner.s,
             data,
-            marker: marker::PhantomData,
+            marker: PhantomData,
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: inner.resource_span,
         })
     }
 }
 
 impl<'a, T: ?Sized> Drop for MappedMutexGuard<'a, T> {
     fn drop(&mut self) {
-        self.s.release(1)
+        self.s.release(1);
+
+        #[cfg(all(tokio_unstable, feature = "tracing"))]
+        self.resource_span.in_scope(|| {
+            tracing::trace!(
+                target: "runtime::resource::state_update",
+                locked = false,
+            );
+        });
     }
 }
 
@@ -1023,3 +1259,111 @@ impl<'a, T: ?Sized + fmt::Display> fmt::Display for MappedMutexGuard<'a, T> {
         fmt::Display::fmt(&**self, f)
     }
 }
+
+// === impl OwnedMappedMutexGuard ===
+
+impl<T: ?Sized, U: ?Sized> OwnedMappedMutexGuard<T, U> {
+    fn skip_drop(self) -> OwnedMappedMutexGuardInner<T, U> {
+        let me = mem::ManuallyDrop::new(self);
+        // SAFETY: This duplicates the values in every field of the guard, then
+        // forgets the originals, so in the end no value is duplicated.
+        unsafe {
+            OwnedMappedMutexGuardInner {
+                data: me.data,
+                lock: ptr::read(&me.lock),
+                #[cfg(all(tokio_unstable, feature = "tracing"))]
+                resource_span: ptr::read(&me.resource_span),
+            }
+        }
+    }
+
+    /// Makes a new [`OwnedMappedMutexGuard`] for a component of the locked data.
+    ///
+    /// This operation cannot fail as the [`OwnedMappedMutexGuard`] passed in already locked the mutex.
+    ///
+    /// This is an associated function that needs to be used as `OwnedMappedMutexGuard::map(...)`. A method
+    /// would interfere with methods of the same name on the contents of the locked data.
+    ///
+    /// [`OwnedMappedMutexGuard`]: struct@OwnedMappedMutexGuard
+    #[inline]
+    pub fn map<S, F>(mut this: Self, f: F) -> OwnedMappedMutexGuard<T, S>
+    where
+        F: FnOnce(&mut U) -> &mut S,
+    {
+        let data = f(&mut *this) as *mut S;
+        let inner = this.skip_drop();
+        OwnedMappedMutexGuard {
+            data,
+            lock: inner.lock,
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: inner.resource_span,
+        }
+    }
+
+    /// Attempts to make a new [`OwnedMappedMutexGuard`] for a component of the locked data. The
+    /// original guard is returned if the closure returns `None`.
+    ///
+    /// This operation cannot fail as the [`OwnedMutexGuard`] passed in already locked the mutex.
+    ///
+    /// This is an associated function that needs to be used as `OwnedMutexGuard::try_map(...)`. A
+    /// method would interfere with methods of the same name on the contents of the locked data.
+    ///
+    /// [`OwnedMutexGuard`]: struct@OwnedMutexGuard
+    /// [`OwnedMappedMutexGuard`]: struct@OwnedMappedMutexGuard
+    #[inline]
+    pub fn try_map<S, F>(mut this: Self, f: F) -> Result<OwnedMappedMutexGuard<T, S>, Self>
+    where
+        F: FnOnce(&mut U) -> Option<&mut S>,
+    {
+        let data = match f(&mut *this) {
+            Some(data) => data as *mut S,
+            None => return Err(this),
+        };
+        let inner = this.skip_drop();
+        Ok(OwnedMappedMutexGuard {
+            data,
+            lock: inner.lock,
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: inner.resource_span,
+        })
+    }
+}
+
+impl<T: ?Sized, U: ?Sized> Drop for OwnedMappedMutexGuard<T, U> {
+    fn drop(&mut self) {
+        self.lock.s.release(1);
+
+        #[cfg(all(tokio_unstable, feature = "tracing"))]
+        self.resource_span.in_scope(|| {
+            tracing::trace!(
+                target: "runtime::resource::state_update",
+                locked = false,
+            );
+        });
+    }
+}
+
+impl<T: ?Sized, U: ?Sized> Deref for OwnedMappedMutexGuard<T, U> {
+    type Target = U;
+    fn deref(&self) -> &Self::Target {
+        unsafe { &*self.data }
+    }
+}
+
+impl<T: ?Sized, U: ?Sized> DerefMut for OwnedMappedMutexGuard<T, U> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        unsafe { &mut *self.data }
+    }
+}
+
+impl<T: ?Sized, U: ?Sized + fmt::Debug> fmt::Debug for OwnedMappedMutexGuard<T, U> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&**self, f)
+    }
+}
+
+impl<T: ?Sized, U: ?Sized + fmt::Display> fmt::Display for OwnedMappedMutexGuard<T, U> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(&**self, f)
+    }
+}
diff --git a/tokio/src/sync/notify.rs b/tokio/src/sync/notify.rs
index efe16f9f8ef..9044eda7fd8 100644
--- a/tokio/src/sync/notify.rs
+++ b/tokio/src/sync/notify.rs
@@ -7,7 +7,7 @@
 
 use crate::loom::sync::atomic::AtomicUsize;
 use crate::loom::sync::Mutex;
-use crate::util::linked_list::{self, LinkedList};
+use crate::util::linked_list::{self, GuardedLinkedList, LinkedList};
 use crate::util::WakeList;
 
 use std::cell::UnsafeCell;
@@ -20,6 +20,7 @@ use std::sync::atomic::Ordering::SeqCst;
 use std::task::{Context, Poll, Waker};
 
 type WaitList = LinkedList<Waiter, <Waiter as linked_list::Link>::Target>;
+type GuardedWaitList = GuardedLinkedList<Waiter, <Waiter as linked_list::Link>::Target>;
 
 /// Notifies a single task to wake up.
 ///
@@ -198,10 +199,16 @@ type WaitList = LinkedList<Waiter, <Waiter as linked_list::Link>::Target>;
 /// [`Semaphore`]: crate::sync::Semaphore
 #[derive(Debug)]
 pub struct Notify {
-    // This uses 2 bits to store one of `EMPTY`,
+    // `state` uses 2 bits to store one of `EMPTY`,
     // `WAITING` or `NOTIFIED`. The rest of the bits
     // are used to store the number of times `notify_waiters`
     // was called.
+    //
+    // Throughout the code there are two assumptions:
+    // - state can be transitioned *from* `WAITING` only if
+    //   `waiters` lock is held
+    // - number of times `notify_waiters` was called can
+    //   be modified only if `waiters` lock is held
     state: AtomicUsize,
     waiters: Mutex<WaitList>,
 }
@@ -229,6 +236,17 @@ struct Waiter {
     _p: PhantomPinned,
 }
 
+impl Waiter {
+    fn new() -> Waiter {
+        Waiter {
+            pointers: linked_list::Pointers::new(),
+            waker: None,
+            notified: None,
+            _p: PhantomPinned,
+        }
+    }
+}
+
 generate_addr_of_methods! {
     impl<> Waiter {
         unsafe fn addr_of_pointers(self: NonNull<Self>) -> NonNull<linked_list::Pointers<Waiter>> {
@@ -237,6 +255,59 @@ generate_addr_of_methods! {
     }
 }
 
+/// List used in `Notify::notify_waiters`. It wraps a guarded linked list
+/// and gates the access to it on `notify.waiters` mutex. It also empties
+/// the list on drop.
+struct NotifyWaitersList<'a> {
+    list: GuardedWaitList,
+    is_empty: bool,
+    notify: &'a Notify,
+}
+
+impl<'a> NotifyWaitersList<'a> {
+    fn new(
+        unguarded_list: WaitList,
+        guard: Pin<&'a mut UnsafeCell<Waiter>>,
+        notify: &'a Notify,
+    ) -> NotifyWaitersList<'a> {
+        // Safety: pointer to the guarding waiter is not null.
+        let guard_ptr = unsafe { NonNull::new_unchecked(guard.get()) };
+        let list = unguarded_list.into_guarded(guard_ptr);
+        NotifyWaitersList {
+            list,
+            is_empty: false,
+            notify,
+        }
+    }
+
+    /// Removes the last element from the guarded list. Modifying this list
+    /// requires an exclusive access to the main list in `Notify`.
+    fn pop_back_locked(&mut self, _waiters: &mut WaitList) -> Option<NonNull<Waiter>> {
+        let result = self.list.pop_back();
+        if result.is_none() {
+            // Save information about emptiness to avoid waiting for lock
+            // in the destructor.
+            self.is_empty = true;
+        }
+        result
+    }
+}
+
+impl Drop for NotifyWaitersList<'_> {
+    fn drop(&mut self) {
+        // If the list is not empty, we unlink all waiters from it.
+        // We do not wake the waiters to avoid double panics.
+        if !self.is_empty {
+            let _lock_guard = self.notify.waiters.lock();
+            while let Some(mut waiter) = self.list.pop_back() {
+                // Safety: we hold the lock.
+                let waiter = unsafe { waiter.as_mut() };
+                waiter.notified = Some(NotificationType::AllWaiters);
+            }
+        }
+    }
+}
+
 /// Future returned from [`Notify::notified()`].
 ///
 /// This future is fused, so once it has completed, any future calls to poll
@@ -249,6 +320,9 @@ pub struct Notified<'a> {
     /// The current state of the receiving process.
     state: State,
 
+    /// Number of calls to `notify_waiters` at the time of creation.
+    notify_waiters_calls: usize,
+
     /// Entry in the waiter `LinkedList`.
     waiter: UnsafeCell<Waiter>,
 }
@@ -258,7 +332,7 @@ unsafe impl<'a> Sync for Notified<'a> {}
 
 #[derive(Debug)]
 enum State {
-    Init(usize),
+    Init,
     Waiting,
     Done,
 }
@@ -383,17 +457,13 @@ impl Notify {
     /// ```
     pub fn notified(&self) -> Notified<'_> {
         // we load the number of times notify_waiters
-        // was called and store that in our initial state
+        // was called and store that in the future.
         let state = self.state.load(SeqCst);
         Notified {
             notify: self,
-            state: State::Init(state >> NOTIFY_WAITERS_SHIFT),
-            waiter: UnsafeCell::new(Waiter {
-                pointers: linked_list::Pointers::new(),
-                waker: None,
-                notified: None,
-                _p: PhantomPinned,
-            }),
+            state: State::Init,
+            notify_waiters_calls: get_num_notify_waiters_calls(state),
+            waiter: UnsafeCell::new(Waiter::new()),
         }
     }
 
@@ -500,12 +570,9 @@ impl Notify {
     /// }
     /// ```
     pub fn notify_waiters(&self) {
-        let mut wakers = WakeList::new();
-
-        // There are waiters, the lock must be acquired to notify.
         let mut waiters = self.waiters.lock();
 
-        // The state must be reloaded while the lock is held. The state may only
+        // The state must be loaded while the lock is held. The state may only
         // transition out of WAITING while the lock is held.
         let curr = self.state.load(SeqCst);
 
@@ -516,12 +583,30 @@ impl Notify {
             return;
         }
 
-        // At this point, it is guaranteed that the state will not
-        // concurrently change, as holding the lock is required to
-        // transition **out** of `WAITING`.
+        // Increment the number of times this method was called
+        // and transition to empty.
+        let new_state = set_state(inc_num_notify_waiters_calls(curr), EMPTY);
+        self.state.store(new_state, SeqCst);
+
+        // It is critical for `GuardedLinkedList` safety that the guard node is
+        // pinned in memory and is not dropped until the guarded list is dropped.
+        let guard = UnsafeCell::new(Waiter::new());
+        pin!(guard);
+
+        // We move all waiters to a secondary list. It uses a `GuardedLinkedList`
+        // underneath to allow every waiter to safely remove itself from it.
+        //
+        // * This list will be still guarded by the `waiters` lock.
+        //   `NotifyWaitersList` wrapper makes sure we hold the lock to modify it.
+        // * This wrapper will empty the list on drop. It is critical for safety
+        //   that we will not leave any list entry with a pointer to the local
+        //   guard node after this function returns / panics.
+        let mut list = NotifyWaitersList::new(std::mem::take(&mut *waiters), guard, self);
+
+        let mut wakers = WakeList::new();
         'outer: loop {
             while wakers.can_push() {
-                match waiters.pop_back() {
+                match list.pop_back_locked(&mut waiters) {
                     Some(mut waiter) => {
                         // Safety: `waiters` lock is still held.
                         let waiter = unsafe { waiter.as_mut() };
@@ -540,20 +625,17 @@ impl Notify {
                 }
             }
 
+            // Release the lock before notifying.
             drop(waiters);
 
+            // One of the wakers may panic, but the remaining waiters will still
+            // be unlinked from the list in `NotifyWaitersList` destructor.
             wakers.wake_all();
 
             // Acquire the lock again.
             waiters = self.waiters.lock();
         }
 
-        // All waiters will be notified, the state must be transitioned to
-        // `EMPTY`. As transitioning **from** `WAITING` requires the lock to be
-        // held, a `store` is sufficient.
-        let new = set_state(inc_num_notify_waiters_calls(curr), EMPTY);
-        self.state.store(new, SeqCst);
-
         // Release the lock before notifying
         drop(waiters);
 
@@ -730,26 +812,32 @@ impl Notified<'_> {
 
     /// A custom `project` implementation is used in place of `pin-project-lite`
     /// as a custom drop implementation is needed.
-    fn project(self: Pin<&mut Self>) -> (&Notify, &mut State, &UnsafeCell<Waiter>) {
+    fn project(self: Pin<&mut Self>) -> (&Notify, &mut State, &usize, &UnsafeCell<Waiter>) {
         unsafe {
-            // Safety: both `notify` and `state` are `Unpin`.
+            // Safety: `notify`, `state` and `notify_waiters_calls` are `Unpin`.
 
             is_unpin::<&Notify>();
             is_unpin::<AtomicUsize>();
+            is_unpin::<usize>();
 
             let me = self.get_unchecked_mut();
-            (me.notify, &mut me.state, &me.waiter)
+            (
+                me.notify,
+                &mut me.state,
+                &me.notify_waiters_calls,
+                &me.waiter,
+            )
         }
     }
 
     fn poll_notified(self: Pin<&mut Self>, waker: Option<&Waker>) -> Poll<()> {
         use State::*;
 
-        let (notify, state, waiter) = self.project();
+        let (notify, state, notify_waiters_calls, waiter) = self.project();
 
         loop {
             match *state {
-                Init(initial_notify_waiters_calls) => {
+                Init => {
                     let curr = notify.state.load(SeqCst);
 
                     // Optimistically try acquiring a pending notification
@@ -779,7 +867,7 @@ impl Notified<'_> {
 
                     // if notify_waiters has been called after the future
                     // was created, then we are done
-                    if get_num_notify_waiters_calls(curr) != initial_notify_waiters_calls {
+                    if get_num_notify_waiters_calls(curr) != *notify_waiters_calls {
                         *state = Done;
                         return Poll::Ready(());
                     }
@@ -829,10 +917,14 @@ impl Notified<'_> {
                         }
                     }
 
+                    let mut old_waker = None;
                     if waker.is_some() {
                         // Safety: called while locked.
+                        //
+                        // The use of `old_waiter` here is not necessary, as the field is always
+                        // None when we reach this line.
                         unsafe {
-                            (*waiter.get()).waker = waker;
+                            old_waker = std::mem::replace(&mut (*waiter.get()).waker, waker);
                         }
                     }
 
@@ -843,24 +935,44 @@ impl Notified<'_> {
 
                     *state = Waiting;
 
+                    drop(waiters);
+                    drop(old_waker);
+
                     return Poll::Pending;
                 }
                 Waiting => {
-                    // Currently in the "Waiting" state, implying the caller has
-                    // a waiter stored in the waiter list (guarded by
-                    // `notify.waiters`). In order to access the waker fields,
-                    // we must hold the lock.
+                    // Currently in the "Waiting" state, implying the caller has a waiter stored in
+                    // a waiter list (guarded by `notify.waiters`). In order to access the waker
+                    // fields, we must acquire the lock.
 
-                    let waiters = notify.waiters.lock();
+                    let mut waiters = notify.waiters.lock();
+
+                    // Load the state with the lock held.
+                    let curr = notify.state.load(SeqCst);
 
                     // Safety: called while locked
                     let w = unsafe { &mut *waiter.get() };
+                    let mut old_waker = None;
 
                     if w.notified.is_some() {
-                        // Our waker has been notified. Reset the fields and
-                        // remove it from the list.
-                        w.waker = None;
+                        // Our waker has been notified and our waiter is already removed from
+                        // the list. Reset the notification and convert to `Done`.
+                        old_waker = std::mem::take(&mut w.waker);
                         w.notified = None;
+                        *state = Done;
+                    } else if get_num_notify_waiters_calls(curr) != *notify_waiters_calls {
+                        // Before we add a waiter to the list we check if these numbers are
+                        // different while holding the lock. If these numbers are different now,
+                        // it means that there is a call to `notify_waiters` in progress and this
+                        // waiter must be contained by a guarded list used in `notify_waiters`.
+                        // We can treat the waiter as notified and remove it from the list, as
+                        // it would have been notified in the `notify_waiters` call anyways.
+
+                        old_waker = std::mem::take(&mut w.waker);
+
+                        // Safety: we hold the lock, so we have an exclusive access to the list.
+                        // The list is used in `notify_waiters`, so it must be guarded.
+                        unsafe { waiters.remove(NonNull::new_unchecked(w)) };
 
                         *state = Done;
                     } else {
@@ -871,10 +983,14 @@ impl Notified<'_> {
                                 None => true,
                             };
                             if should_update {
-                                w.waker = Some(waker.clone());
+                                old_waker = std::mem::replace(&mut w.waker, Some(waker.clone()));
                             }
                         }
 
+                        // Drop the old waker after releasing the lock.
+                        drop(waiters);
+                        drop(old_waker);
+
                         return Poll::Pending;
                     }
 
@@ -884,6 +1000,9 @@ impl Notified<'_> {
                     // is helpful to visualize the scope of the critical
                     // section.
                     drop(waiters);
+
+                    // Drop the old waker after releasing the lock.
+                    drop(old_waker);
                 }
                 Done => {
                     return Poll::Ready(());
@@ -906,7 +1025,7 @@ impl Drop for Notified<'_> {
         use State::*;
 
         // Safety: The type only transitions to a "Waiting" state when pinned.
-        let (notify, state, waiter) = unsafe { Pin::new_unchecked(self).project() };
+        let (notify, state, _, waiter) = unsafe { Pin::new_unchecked(self).project() };
 
         // This is where we ensure safety. The `Notified` value is being
         // dropped, which means we must ensure that the waiter entry is no
@@ -917,8 +1036,10 @@ impl Drop for Notified<'_> {
 
             // remove the entry from the list (if not already removed)
             //
-            // safety: the waiter is only added to `waiters` by virtue of it
-            // being the only `LinkedList` available to the type.
+            // Safety: we hold the lock, so we have an exclusive access to every list the
+            // waiter may be contained in. If the node is not contained in the `waiters`
+            // list, then it is contained by a guarded list used by `notify_waiters` and
+            // in such case it must be a middle node.
             unsafe { waiters.remove(NonNull::new_unchecked(waiter.get())) };
 
             if waiters.is_empty() && get_state(notify_state) == WAITING {
diff --git a/tokio/src/sync/oneshot.rs b/tokio/src/sync/oneshot.rs
index fcd7a32e8e8..da64899d095 100644
--- a/tokio/src/sync/oneshot.rs
+++ b/tokio/src/sync/oneshot.rs
@@ -12,6 +12,10 @@
 //! Since the `send` method is not async, it can be used anywhere. This includes
 //! sending between two runtimes, and using it from non-async code.
 //!
+//! If the [`Receiver`] is closed before receiving a message which has already
+//! been sent, the message will remain in the channel until the receiver is
+//! dropped, at which point the message will be dropped immediately.
+//!
 //! # Examples
 //!
 //! ```
@@ -1056,6 +1060,7 @@ impl<T> Receiver<T> {
     /// ```
     #[track_caller]
     #[cfg(feature = "sync")]
+    #[cfg_attr(docsrs, doc(alias = "recv_blocking"))]
     pub fn blocking_recv(self) -> Result<T, RecvError> {
         crate::future::block_on(self)
     }
diff --git a/tokio/src/sync/rwlock.rs b/tokio/src/sync/rwlock.rs
index 0492e4e9d39..c332ede2bbe 100644
--- a/tokio/src/sync/rwlock.rs
+++ b/tokio/src/sync/rwlock.rs
@@ -5,7 +5,6 @@ use crate::util::trace;
 use std::cell::UnsafeCell;
 use std::marker;
 use std::marker::PhantomData;
-use std::mem::ManuallyDrop;
 use std::sync::Arc;
 
 pub(crate) mod owned_read_guard;
@@ -423,23 +422,33 @@ impl<T: ?Sized> RwLock<T> {
     /// }
     /// ```
     pub async fn read(&self) -> RwLockReadGuard<'_, T> {
+        let acquire_fut = async {
+            self.s.acquire(1).await.unwrap_or_else(|_| {
+                // The semaphore was closed. but, we never explicitly close it, and we have a
+                // handle to it through the Arc, which means that this can never happen.
+                unreachable!()
+            });
+
+            RwLockReadGuard {
+                s: &self.s,
+                data: self.c.get(),
+                marker: PhantomData,
+                #[cfg(all(tokio_unstable, feature = "tracing"))]
+                resource_span: self.resource_span.clone(),
+            }
+        };
+
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let inner = trace::async_op(
-            || self.s.acquire(1),
+        let acquire_fut = trace::async_op(
+            move || acquire_fut,
             self.resource_span.clone(),
             "RwLock::read",
             "poll",
             false,
         );
 
-        #[cfg(not(all(tokio_unstable, feature = "tracing")))]
-        let inner = self.s.acquire(1);
-
-        inner.await.unwrap_or_else(|_| {
-            // The semaphore was closed. but, we never explicitly close it, and we have a
-            // handle to it through the Arc, which means that this can never happen.
-            unreachable!()
-        });
+        #[allow(clippy::let_and_return)] // this lint triggers when disabling tracing
+        let guard = acquire_fut.await;
 
         #[cfg(all(tokio_unstable, feature = "tracing"))]
         self.resource_span.in_scope(|| {
@@ -450,13 +459,7 @@ impl<T: ?Sized> RwLock<T> {
             )
         });
 
-        RwLockReadGuard {
-            s: &self.s,
-            data: self.c.get(),
-            marker: marker::PhantomData,
-            #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span: self.resource_span.clone(),
-        }
+        guard
     }
 
     /// Blockingly locks this `RwLock` with shared read access.
@@ -565,25 +568,38 @@ impl<T: ?Sized> RwLock<T> {
     /// ```
     pub async fn read_owned(self: Arc<Self>) -> OwnedRwLockReadGuard<T> {
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let inner = trace::async_op(
-            || self.s.acquire(1),
-            self.resource_span.clone(),
+        let resource_span = self.resource_span.clone();
+
+        let acquire_fut = async {
+            self.s.acquire(1).await.unwrap_or_else(|_| {
+                // The semaphore was closed. but, we never explicitly close it, and we have a
+                // handle to it through the Arc, which means that this can never happen.
+                unreachable!()
+            });
+
+            OwnedRwLockReadGuard {
+                #[cfg(all(tokio_unstable, feature = "tracing"))]
+                resource_span: self.resource_span.clone(),
+                data: self.c.get(),
+                lock: self,
+                _p: PhantomData,
+            }
+        };
+
+        #[cfg(all(tokio_unstable, feature = "tracing"))]
+        let acquire_fut = trace::async_op(
+            move || acquire_fut,
+            resource_span,
             "RwLock::read_owned",
             "poll",
             false,
         );
 
-        #[cfg(not(all(tokio_unstable, feature = "tracing")))]
-        let inner = self.s.acquire(1);
-
-        inner.await.unwrap_or_else(|_| {
-            // The semaphore was closed. but, we never explicitly close it, and we have a
-            // handle to it through the Arc, which means that this can never happen.
-            unreachable!()
-        });
+        #[allow(clippy::let_and_return)] // this lint triggers when disabling tracing
+        let guard = acquire_fut.await;
 
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        self.resource_span.in_scope(|| {
+        guard.resource_span.in_scope(|| {
             tracing::trace!(
             target: "runtime::resource::state_update",
             current_readers = 1,
@@ -591,16 +607,7 @@ impl<T: ?Sized> RwLock<T> {
             )
         });
 
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = self.resource_span.clone();
-
-        OwnedRwLockReadGuard {
-            data: self.c.get(),
-            lock: ManuallyDrop::new(self),
-            _p: PhantomData,
-            #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
-        }
+        guard
     }
 
     /// Attempts to acquire this `RwLock` with shared read access.
@@ -642,6 +649,14 @@ impl<T: ?Sized> RwLock<T> {
             Err(TryAcquireError::Closed) => unreachable!(),
         }
 
+        let guard = RwLockReadGuard {
+            s: &self.s,
+            data: self.c.get(),
+            marker: marker::PhantomData,
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: self.resource_span.clone(),
+        };
+
         #[cfg(all(tokio_unstable, feature = "tracing"))]
         self.resource_span.in_scope(|| {
             tracing::trace!(
@@ -651,13 +666,7 @@ impl<T: ?Sized> RwLock<T> {
             )
         });
 
-        Ok(RwLockReadGuard {
-            s: &self.s,
-            data: self.c.get(),
-            marker: marker::PhantomData,
-            #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span: self.resource_span.clone(),
-        })
+        Ok(guard)
     }
 
     /// Attempts to acquire this `RwLock` with shared read access.
@@ -705,8 +714,16 @@ impl<T: ?Sized> RwLock<T> {
             Err(TryAcquireError::Closed) => unreachable!(),
         }
 
+        let guard = OwnedRwLockReadGuard {
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: self.resource_span.clone(),
+            data: self.c.get(),
+            lock: self,
+            _p: PhantomData,
+        };
+
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        self.resource_span.in_scope(|| {
+        guard.resource_span.in_scope(|| {
             tracing::trace!(
             target: "runtime::resource::state_update",
             current_readers = 1,
@@ -714,16 +731,7 @@ impl<T: ?Sized> RwLock<T> {
             )
         });
 
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = self.resource_span.clone();
-
-        Ok(OwnedRwLockReadGuard {
-            data: self.c.get(),
-            lock: ManuallyDrop::new(self),
-            _p: PhantomData,
-            #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
-        })
+        Ok(guard)
     }
 
     /// Locks this `RwLock` with exclusive write access, causing the current
@@ -755,23 +763,34 @@ impl<T: ?Sized> RwLock<T> {
     ///}
     /// ```
     pub async fn write(&self) -> RwLockWriteGuard<'_, T> {
+        let acquire_fut = async {
+            self.s.acquire(self.mr).await.unwrap_or_else(|_| {
+                // The semaphore was closed. but, we never explicitly close it, and we have a
+                // handle to it through the Arc, which means that this can never happen.
+                unreachable!()
+            });
+
+            RwLockWriteGuard {
+                permits_acquired: self.mr,
+                s: &self.s,
+                data: self.c.get(),
+                marker: marker::PhantomData,
+                #[cfg(all(tokio_unstable, feature = "tracing"))]
+                resource_span: self.resource_span.clone(),
+            }
+        };
+
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let inner = trace::async_op(
-            || self.s.acquire(self.mr),
+        let acquire_fut = trace::async_op(
+            move || acquire_fut,
             self.resource_span.clone(),
             "RwLock::write",
             "poll",
             false,
         );
 
-        #[cfg(not(all(tokio_unstable, feature = "tracing")))]
-        let inner = self.s.acquire(self.mr);
-
-        inner.await.unwrap_or_else(|_| {
-            // The semaphore was closed. but, we never explicitly close it, and we have a
-            // handle to it through the Arc, which means that this can never happen.
-            unreachable!()
-        });
+        #[allow(clippy::let_and_return)] // this lint triggers when disabling tracing
+        let guard = acquire_fut.await;
 
         #[cfg(all(tokio_unstable, feature = "tracing"))]
         self.resource_span.in_scope(|| {
@@ -782,14 +801,7 @@ impl<T: ?Sized> RwLock<T> {
             )
         });
 
-        RwLockWriteGuard {
-            permits_acquired: self.mr,
-            s: &self.s,
-            data: self.c.get(),
-            marker: marker::PhantomData,
-            #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span: self.resource_span.clone(),
-        }
+        guard
     }
 
     /// Blockingly locks this `RwLock` with exclusive write access.
@@ -884,25 +896,39 @@ impl<T: ?Sized> RwLock<T> {
     /// ```
     pub async fn write_owned(self: Arc<Self>) -> OwnedRwLockWriteGuard<T> {
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let inner = trace::async_op(
-            || self.s.acquire(self.mr),
-            self.resource_span.clone(),
+        let resource_span = self.resource_span.clone();
+
+        let acquire_fut = async {
+            self.s.acquire(self.mr).await.unwrap_or_else(|_| {
+                // The semaphore was closed. but, we never explicitly close it, and we have a
+                // handle to it through the Arc, which means that this can never happen.
+                unreachable!()
+            });
+
+            OwnedRwLockWriteGuard {
+                #[cfg(all(tokio_unstable, feature = "tracing"))]
+                resource_span: self.resource_span.clone(),
+                permits_acquired: self.mr,
+                data: self.c.get(),
+                lock: self,
+                _p: PhantomData,
+            }
+        };
+
+        #[cfg(all(tokio_unstable, feature = "tracing"))]
+        let acquire_fut = trace::async_op(
+            move || acquire_fut,
+            resource_span,
             "RwLock::write_owned",
             "poll",
             false,
         );
 
-        #[cfg(not(all(tokio_unstable, feature = "tracing")))]
-        let inner = self.s.acquire(self.mr);
-
-        inner.await.unwrap_or_else(|_| {
-            // The semaphore was closed. but, we never explicitly close it, and we have a
-            // handle to it through the Arc, which means that this can never happen.
-            unreachable!()
-        });
+        #[allow(clippy::let_and_return)] // this lint triggers when disabling tracing
+        let guard = acquire_fut.await;
 
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        self.resource_span.in_scope(|| {
+        guard.resource_span.in_scope(|| {
             tracing::trace!(
             target: "runtime::resource::state_update",
             write_locked = true,
@@ -910,17 +936,7 @@ impl<T: ?Sized> RwLock<T> {
             )
         });
 
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = self.resource_span.clone();
-
-        OwnedRwLockWriteGuard {
-            permits_acquired: self.mr,
-            data: self.c.get(),
-            lock: ManuallyDrop::new(self),
-            _p: PhantomData,
-            #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
-        }
+        guard
     }
 
     /// Attempts to acquire this `RwLock` with exclusive write access.
@@ -953,6 +969,15 @@ impl<T: ?Sized> RwLock<T> {
             Err(TryAcquireError::Closed) => unreachable!(),
         }
 
+        let guard = RwLockWriteGuard {
+            permits_acquired: self.mr,
+            s: &self.s,
+            data: self.c.get(),
+            marker: marker::PhantomData,
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: self.resource_span.clone(),
+        };
+
         #[cfg(all(tokio_unstable, feature = "tracing"))]
         self.resource_span.in_scope(|| {
             tracing::trace!(
@@ -962,14 +987,7 @@ impl<T: ?Sized> RwLock<T> {
             )
         });
 
-        Ok(RwLockWriteGuard {
-            permits_acquired: self.mr,
-            s: &self.s,
-            data: self.c.get(),
-            marker: marker::PhantomData,
-            #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span: self.resource_span.clone(),
-        })
+        Ok(guard)
     }
 
     /// Attempts to acquire this `RwLock` with exclusive write access.
@@ -1009,8 +1027,17 @@ impl<T: ?Sized> RwLock<T> {
             Err(TryAcquireError::Closed) => unreachable!(),
         }
 
+        let guard = OwnedRwLockWriteGuard {
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: self.resource_span.clone(),
+            permits_acquired: self.mr,
+            data: self.c.get(),
+            lock: self,
+            _p: PhantomData,
+        };
+
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        self.resource_span.in_scope(|| {
+        guard.resource_span.in_scope(|| {
             tracing::trace!(
             target: "runtime::resource::state_update",
             write_locked = true,
@@ -1018,17 +1045,7 @@ impl<T: ?Sized> RwLock<T> {
             )
         });
 
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = self.resource_span.clone();
-
-        Ok(OwnedRwLockWriteGuard {
-            permits_acquired: self.mr,
-            data: self.c.get(),
-            lock: ManuallyDrop::new(self),
-            _p: PhantomData,
-            #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
-        })
+        Ok(guard)
     }
 
     /// Returns a mutable reference to the underlying data.
diff --git a/tokio/src/sync/rwlock/owned_read_guard.rs b/tokio/src/sync/rwlock/owned_read_guard.rs
index 27b71bd988b..273e7b86f2f 100644
--- a/tokio/src/sync/rwlock/owned_read_guard.rs
+++ b/tokio/src/sync/rwlock/owned_read_guard.rs
@@ -1,10 +1,7 @@
 use crate::sync::rwlock::RwLock;
-use std::fmt;
 use std::marker::PhantomData;
-use std::mem;
-use std::mem::ManuallyDrop;
-use std::ops;
 use std::sync::Arc;
+use std::{fmt, mem, ops, ptr};
 
 /// Owned RAII structure used to release the shared read access of a lock when
 /// dropped.
@@ -14,16 +11,40 @@ use std::sync::Arc;
 ///
 /// [`read_owned`]: method@crate::sync::RwLock::read_owned
 /// [`RwLock`]: struct@crate::sync::RwLock
+#[clippy::has_significant_drop]
 pub struct OwnedRwLockReadGuard<T: ?Sized, U: ?Sized = T> {
+    // When changing the fields in this struct, make sure to update the
+    // `skip_drop` method.
     #[cfg(all(tokio_unstable, feature = "tracing"))]
     pub(super) resource_span: tracing::Span,
-    // ManuallyDrop allows us to destructure into this field without running the destructor.
-    pub(super) lock: ManuallyDrop<Arc<RwLock<T>>>,
+    pub(super) lock: Arc<RwLock<T>>,
     pub(super) data: *const U,
     pub(super) _p: PhantomData<T>,
 }
 
+#[allow(dead_code)] // Unused fields are still used in Drop.
+struct Inner<T: ?Sized, U: ?Sized> {
+    #[cfg(all(tokio_unstable, feature = "tracing"))]
+    resource_span: tracing::Span,
+    lock: Arc<RwLock<T>>,
+    data: *const U,
+}
+
 impl<T: ?Sized, U: ?Sized> OwnedRwLockReadGuard<T, U> {
+    fn skip_drop(self) -> Inner<T, U> {
+        let me = mem::ManuallyDrop::new(self);
+        // SAFETY: This duplicates the values in every field of the guard, then
+        // forgets the originals, so in the end no value is duplicated.
+        unsafe {
+            Inner {
+                #[cfg(all(tokio_unstable, feature = "tracing"))]
+                resource_span: ptr::read(&me.resource_span),
+                lock: ptr::read(&me.lock),
+                data: me.data,
+            }
+        }
+    }
+
     /// Makes a new `OwnedRwLockReadGuard` for a component of the locked data.
     /// This operation cannot fail as the `OwnedRwLockReadGuard` passed in
     /// already locked the data.
@@ -52,23 +73,19 @@ impl<T: ?Sized, U: ?Sized> OwnedRwLockReadGuard<T, U> {
     /// # }
     /// ```
     #[inline]
-    pub fn map<F, V: ?Sized>(mut this: Self, f: F) -> OwnedRwLockReadGuard<T, V>
+    pub fn map<F, V: ?Sized>(this: Self, f: F) -> OwnedRwLockReadGuard<T, V>
     where
         F: FnOnce(&U) -> &V,
     {
         let data = f(&*this) as *const V;
-        let lock = unsafe { ManuallyDrop::take(&mut this.lock) };
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = this.resource_span.clone();
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(this);
+        let this = this.skip_drop();
 
         OwnedRwLockReadGuard {
-            lock: ManuallyDrop::new(lock),
+            lock: this.lock,
             data,
             _p: PhantomData,
             #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
+            resource_span: this.resource_span,
         }
     }
 
@@ -103,7 +120,7 @@ impl<T: ?Sized, U: ?Sized> OwnedRwLockReadGuard<T, U> {
     /// # }
     /// ```
     #[inline]
-    pub fn try_map<F, V: ?Sized>(mut this: Self, f: F) -> Result<OwnedRwLockReadGuard<T, V>, Self>
+    pub fn try_map<F, V: ?Sized>(this: Self, f: F) -> Result<OwnedRwLockReadGuard<T, V>, Self>
     where
         F: FnOnce(&U) -> Option<&V>,
     {
@@ -111,18 +128,14 @@ impl<T: ?Sized, U: ?Sized> OwnedRwLockReadGuard<T, U> {
             Some(data) => data as *const V,
             None => return Err(this),
         };
-        let lock = unsafe { ManuallyDrop::take(&mut this.lock) };
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = this.resource_span.clone();
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(this);
+        let this = this.skip_drop();
 
         Ok(OwnedRwLockReadGuard {
-            lock: ManuallyDrop::new(lock),
+            lock: this.lock,
             data,
             _p: PhantomData,
             #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
+            resource_span: this.resource_span,
         })
     }
 }
@@ -156,7 +169,6 @@ where
 impl<T: ?Sized, U: ?Sized> Drop for OwnedRwLockReadGuard<T, U> {
     fn drop(&mut self) {
         self.lock.s.release(1);
-        unsafe { ManuallyDrop::drop(&mut self.lock) };
 
         #[cfg(all(tokio_unstable, feature = "tracing"))]
         self.resource_span.in_scope(|| {
diff --git a/tokio/src/sync/rwlock/owned_write_guard.rs b/tokio/src/sync/rwlock/owned_write_guard.rs
index dbedab4cbb2..cbc77f6f4a2 100644
--- a/tokio/src/sync/rwlock/owned_write_guard.rs
+++ b/tokio/src/sync/rwlock/owned_write_guard.rs
@@ -1,11 +1,9 @@
 use crate::sync::rwlock::owned_read_guard::OwnedRwLockReadGuard;
 use crate::sync::rwlock::owned_write_guard_mapped::OwnedRwLockMappedWriteGuard;
 use crate::sync::rwlock::RwLock;
-use std::fmt;
 use std::marker::PhantomData;
-use std::mem::{self, ManuallyDrop};
-use std::ops;
 use std::sync::Arc;
+use std::{fmt, mem, ops, ptr};
 
 /// Owned RAII structure used to release the exclusive write access of a lock when
 /// dropped.
@@ -15,17 +13,43 @@ use std::sync::Arc;
 ///
 /// [`write_owned`]: method@crate::sync::RwLock::write_owned
 /// [`RwLock`]: struct@crate::sync::RwLock
+#[clippy::has_significant_drop]
 pub struct OwnedRwLockWriteGuard<T: ?Sized> {
+    // When changing the fields in this struct, make sure to update the
+    // `skip_drop` method.
     #[cfg(all(tokio_unstable, feature = "tracing"))]
     pub(super) resource_span: tracing::Span,
     pub(super) permits_acquired: u32,
-    // ManuallyDrop allows us to destructure into this field without running the destructor.
-    pub(super) lock: ManuallyDrop<Arc<RwLock<T>>>,
+    pub(super) lock: Arc<RwLock<T>>,
     pub(super) data: *mut T,
     pub(super) _p: PhantomData<T>,
 }
 
+#[allow(dead_code)] // Unused fields are still used in Drop.
+struct Inner<T: ?Sized> {
+    #[cfg(all(tokio_unstable, feature = "tracing"))]
+    resource_span: tracing::Span,
+    permits_acquired: u32,
+    lock: Arc<RwLock<T>>,
+    data: *const T,
+}
+
 impl<T: ?Sized> OwnedRwLockWriteGuard<T> {
+    fn skip_drop(self) -> Inner<T> {
+        let me = mem::ManuallyDrop::new(self);
+        // SAFETY: This duplicates the values in every field of the guard, then
+        // forgets the originals, so in the end no value is duplicated.
+        unsafe {
+            Inner {
+                #[cfg(all(tokio_unstable, feature = "tracing"))]
+                resource_span: ptr::read(&me.resource_span),
+                permits_acquired: me.permits_acquired,
+                lock: ptr::read(&me.lock),
+                data: me.data,
+            }
+        }
+    }
+
     /// Makes a new [`OwnedRwLockMappedWriteGuard`] for a component of the locked
     /// data.
     ///
@@ -64,20 +88,15 @@ impl<T: ?Sized> OwnedRwLockWriteGuard<T> {
         F: FnOnce(&mut T) -> &mut U,
     {
         let data = f(&mut *this) as *mut U;
-        let lock = unsafe { ManuallyDrop::take(&mut this.lock) };
-        let permits_acquired = this.permits_acquired;
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = this.resource_span.clone();
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(this);
+        let this = this.skip_drop();
 
         OwnedRwLockMappedWriteGuard {
-            permits_acquired,
-            lock: ManuallyDrop::new(lock),
+            permits_acquired: this.permits_acquired,
+            lock: this.lock,
             data,
             _p: PhantomData,
             #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
+            resource_span: this.resource_span,
         }
     }
 
@@ -128,21 +147,15 @@ impl<T: ?Sized> OwnedRwLockWriteGuard<T> {
             Some(data) => data as *mut U,
             None => return Err(this),
         };
-        let permits_acquired = this.permits_acquired;
-        let lock = unsafe { ManuallyDrop::take(&mut this.lock) };
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = this.resource_span.clone();
-
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(this);
+        let this = this.skip_drop();
 
         Ok(OwnedRwLockMappedWriteGuard {
-            permits_acquired,
-            lock: ManuallyDrop::new(lock),
+            permits_acquired: this.permits_acquired,
+            lock: this.lock,
             data,
             _p: PhantomData,
             #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
+            resource_span: this.resource_span,
         })
     }
 
@@ -191,15 +204,22 @@ impl<T: ?Sized> OwnedRwLockWriteGuard<T> {
     /// assert_eq!(*lock.read().await, 2, "second writer obtained write lock");
     /// # }
     /// ```
-    pub fn downgrade(mut self) -> OwnedRwLockReadGuard<T> {
-        let lock = unsafe { ManuallyDrop::take(&mut self.lock) };
-        let data = self.data;
-        let to_release = (self.permits_acquired - 1) as usize;
+    pub fn downgrade(self) -> OwnedRwLockReadGuard<T> {
+        let this = self.skip_drop();
+        let guard = OwnedRwLockReadGuard {
+            lock: this.lock,
+            data: this.data,
+            _p: PhantomData,
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: this.resource_span,
+        };
 
         // Release all but one of the permits held by the write guard
-        lock.s.release(to_release);
+        let to_release = (this.permits_acquired - 1) as usize;
+        guard.lock.s.release(to_release);
+
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        self.resource_span.in_scope(|| {
+        guard.resource_span.in_scope(|| {
             tracing::trace!(
             target: "runtime::resource::state_update",
             write_locked = false,
@@ -208,7 +228,7 @@ impl<T: ?Sized> OwnedRwLockWriteGuard<T> {
         });
 
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        self.resource_span.in_scope(|| {
+        guard.resource_span.in_scope(|| {
             tracing::trace!(
             target: "runtime::resource::state_update",
             current_readers = 1,
@@ -216,18 +236,7 @@ impl<T: ?Sized> OwnedRwLockWriteGuard<T> {
             )
         });
 
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = self.resource_span.clone();
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(self);
-
-        OwnedRwLockReadGuard {
-            lock: ManuallyDrop::new(lock),
-            data,
-            _p: PhantomData,
-            #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
-        }
+        guard
     }
 }
 
@@ -266,6 +275,7 @@ where
 impl<T: ?Sized> Drop for OwnedRwLockWriteGuard<T> {
     fn drop(&mut self) {
         self.lock.s.release(self.permits_acquired as usize);
+
         #[cfg(all(tokio_unstable, feature = "tracing"))]
         self.resource_span.in_scope(|| {
             tracing::trace!(
@@ -274,6 +284,5 @@ impl<T: ?Sized> Drop for OwnedRwLockWriteGuard<T> {
             write_locked.op = "override",
             )
         });
-        unsafe { ManuallyDrop::drop(&mut self.lock) };
     }
 }
diff --git a/tokio/src/sync/rwlock/owned_write_guard_mapped.rs b/tokio/src/sync/rwlock/owned_write_guard_mapped.rs
index 55a24d96ac3..9f4952100a5 100644
--- a/tokio/src/sync/rwlock/owned_write_guard_mapped.rs
+++ b/tokio/src/sync/rwlock/owned_write_guard_mapped.rs
@@ -1,9 +1,7 @@
 use crate::sync::rwlock::RwLock;
-use std::fmt;
 use std::marker::PhantomData;
-use std::mem::{self, ManuallyDrop};
-use std::ops;
 use std::sync::Arc;
+use std::{fmt, mem, ops, ptr};
 
 /// Owned RAII structure used to release the exclusive write access of a lock when
 /// dropped.
@@ -14,17 +12,43 @@ use std::sync::Arc;
 ///
 /// [mapping]: method@crate::sync::OwnedRwLockWriteGuard::map
 /// [`OwnedRwLockWriteGuard`]: struct@crate::sync::OwnedRwLockWriteGuard
+#[clippy::has_significant_drop]
 pub struct OwnedRwLockMappedWriteGuard<T: ?Sized, U: ?Sized = T> {
+    // When changing the fields in this struct, make sure to update the
+    // `skip_drop` method.
     #[cfg(all(tokio_unstable, feature = "tracing"))]
     pub(super) resource_span: tracing::Span,
     pub(super) permits_acquired: u32,
-    // ManuallyDrop allows us to destructure into this field without running the destructor.
-    pub(super) lock: ManuallyDrop<Arc<RwLock<T>>>,
+    pub(super) lock: Arc<RwLock<T>>,
     pub(super) data: *mut U,
     pub(super) _p: PhantomData<T>,
 }
 
+#[allow(dead_code)] // Unused fields are still used in Drop.
+struct Inner<T: ?Sized, U: ?Sized> {
+    #[cfg(all(tokio_unstable, feature = "tracing"))]
+    resource_span: tracing::Span,
+    permits_acquired: u32,
+    lock: Arc<RwLock<T>>,
+    data: *const U,
+}
+
 impl<T: ?Sized, U: ?Sized> OwnedRwLockMappedWriteGuard<T, U> {
+    fn skip_drop(self) -> Inner<T, U> {
+        let me = mem::ManuallyDrop::new(self);
+        // SAFETY: This duplicates the values in every field of the guard, then
+        // forgets the originals, so in the end no value is duplicated.
+        unsafe {
+            Inner {
+                #[cfg(all(tokio_unstable, feature = "tracing"))]
+                resource_span: ptr::read(&me.resource_span),
+                permits_acquired: me.permits_acquired,
+                lock: ptr::read(&me.lock),
+                data: me.data,
+            }
+        }
+    }
+
     /// Makes a new `OwnedRwLockMappedWriteGuard` for a component of the locked
     /// data.
     ///
@@ -63,20 +87,15 @@ impl<T: ?Sized, U: ?Sized> OwnedRwLockMappedWriteGuard<T, U> {
         F: FnOnce(&mut U) -> &mut V,
     {
         let data = f(&mut *this) as *mut V;
-        let lock = unsafe { ManuallyDrop::take(&mut this.lock) };
-        let permits_acquired = this.permits_acquired;
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = this.resource_span.clone();
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(this);
+        let this = this.skip_drop();
 
         OwnedRwLockMappedWriteGuard {
-            permits_acquired,
-            lock: ManuallyDrop::new(lock),
+            permits_acquired: this.permits_acquired,
+            lock: this.lock,
             data,
             _p: PhantomData,
             #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
+            resource_span: this.resource_span,
         }
     }
 
@@ -125,20 +144,15 @@ impl<T: ?Sized, U: ?Sized> OwnedRwLockMappedWriteGuard<T, U> {
             Some(data) => data as *mut V,
             None => return Err(this),
         };
-        let lock = unsafe { ManuallyDrop::take(&mut this.lock) };
-        let permits_acquired = this.permits_acquired;
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = this.resource_span.clone();
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(this);
+        let this = this.skip_drop();
 
         Ok(OwnedRwLockMappedWriteGuard {
-            permits_acquired,
-            lock: ManuallyDrop::new(lock),
+            permits_acquired: this.permits_acquired,
+            lock: this.lock,
             data,
             _p: PhantomData,
             #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
+            resource_span: this.resource_span,
         })
     }
 }
@@ -178,6 +192,7 @@ where
 impl<T: ?Sized, U: ?Sized> Drop for OwnedRwLockMappedWriteGuard<T, U> {
     fn drop(&mut self) {
         self.lock.s.release(self.permits_acquired as usize);
+
         #[cfg(all(tokio_unstable, feature = "tracing"))]
         self.resource_span.in_scope(|| {
             tracing::trace!(
@@ -186,6 +201,5 @@ impl<T: ?Sized, U: ?Sized> Drop for OwnedRwLockMappedWriteGuard<T, U> {
             write_locked.op = "override",
             )
         });
-        unsafe { ManuallyDrop::drop(&mut self.lock) };
     }
 }
diff --git a/tokio/src/sync/rwlock/read_guard.rs b/tokio/src/sync/rwlock/read_guard.rs
index f5fc1d6de81..a04b59588d5 100644
--- a/tokio/src/sync/rwlock/read_guard.rs
+++ b/tokio/src/sync/rwlock/read_guard.rs
@@ -1,8 +1,6 @@
 use crate::sync::batch_semaphore::Semaphore;
-use std::fmt;
-use std::marker;
-use std::mem;
-use std::ops;
+use std::marker::PhantomData;
+use std::{fmt, mem, ops};
 
 /// RAII structure used to release the shared read access of a lock when
 /// dropped.
@@ -12,16 +10,39 @@ use std::ops;
 ///
 /// [`read`]: method@crate::sync::RwLock::read
 /// [`RwLock`]: struct@crate::sync::RwLock
+#[clippy::has_significant_drop]
 #[must_use = "if unused the RwLock will immediately unlock"]
 pub struct RwLockReadGuard<'a, T: ?Sized> {
+    // When changing the fields in this struct, make sure to update the
+    // `skip_drop` method.
     #[cfg(all(tokio_unstable, feature = "tracing"))]
     pub(super) resource_span: tracing::Span,
     pub(super) s: &'a Semaphore,
     pub(super) data: *const T,
-    pub(super) marker: marker::PhantomData<&'a T>,
+    pub(super) marker: PhantomData<&'a T>,
+}
+
+#[allow(dead_code)] // Unused fields are still used in Drop.
+struct Inner<'a, T: ?Sized> {
+    #[cfg(all(tokio_unstable, feature = "tracing"))]
+    resource_span: tracing::Span,
+    s: &'a Semaphore,
+    data: *const T,
 }
 
 impl<'a, T: ?Sized> RwLockReadGuard<'a, T> {
+    fn skip_drop(self) -> Inner<'a, T> {
+        let me = mem::ManuallyDrop::new(self);
+        // SAFETY: This duplicates the values in every field of the guard, then
+        // forgets the originals, so in the end no value is duplicated.
+        Inner {
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: unsafe { std::ptr::read(&me.resource_span) },
+            s: me.s,
+            data: me.data,
+        }
+    }
+
     /// Makes a new `RwLockReadGuard` for a component of the locked data.
     ///
     /// This operation cannot fail as the `RwLockReadGuard` passed in already
@@ -61,18 +82,14 @@ impl<'a, T: ?Sized> RwLockReadGuard<'a, T> {
         F: FnOnce(&T) -> &U,
     {
         let data = f(&*this) as *const U;
-        let s = this.s;
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = this.resource_span.clone();
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(this);
+        let this = this.skip_drop();
 
         RwLockReadGuard {
-            s,
+            s: this.s,
             data,
-            marker: marker::PhantomData,
+            marker: PhantomData,
             #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
+            resource_span: this.resource_span,
         }
     }
 
@@ -120,18 +137,14 @@ impl<'a, T: ?Sized> RwLockReadGuard<'a, T> {
             Some(data) => data as *const U,
             None => return Err(this),
         };
-        let s = this.s;
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = this.resource_span.clone();
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(this);
+        let this = this.skip_drop();
 
         Ok(RwLockReadGuard {
-            s,
+            s: this.s,
             data,
-            marker: marker::PhantomData,
+            marker: PhantomData,
             #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
+            resource_span: this.resource_span,
         })
     }
 }
diff --git a/tokio/src/sync/rwlock/write_guard.rs b/tokio/src/sync/rwlock/write_guard.rs
index cefa183d996..4527e5581c9 100644
--- a/tokio/src/sync/rwlock/write_guard.rs
+++ b/tokio/src/sync/rwlock/write_guard.rs
@@ -1,10 +1,8 @@
 use crate::sync::batch_semaphore::Semaphore;
 use crate::sync::rwlock::read_guard::RwLockReadGuard;
 use crate::sync::rwlock::write_guard_mapped::RwLockMappedWriteGuard;
-use std::fmt;
-use std::marker;
-use std::mem;
-use std::ops;
+use std::marker::PhantomData;
+use std::{fmt, mem, ops};
 
 /// RAII structure used to release the exclusive write access of a lock when
 /// dropped.
@@ -14,17 +12,42 @@ use std::ops;
 ///
 /// [`write`]: method@crate::sync::RwLock::write
 /// [`RwLock`]: struct@crate::sync::RwLock
+#[clippy::has_significant_drop]
 #[must_use = "if unused the RwLock will immediately unlock"]
 pub struct RwLockWriteGuard<'a, T: ?Sized> {
+    // When changing the fields in this struct, make sure to update the
+    // `skip_drop` method.
     #[cfg(all(tokio_unstable, feature = "tracing"))]
     pub(super) resource_span: tracing::Span,
     pub(super) permits_acquired: u32,
     pub(super) s: &'a Semaphore,
     pub(super) data: *mut T,
-    pub(super) marker: marker::PhantomData<&'a mut T>,
+    pub(super) marker: PhantomData<&'a mut T>,
+}
+
+#[allow(dead_code)] // Unused fields are still used in Drop.
+struct Inner<'a, T: ?Sized> {
+    #[cfg(all(tokio_unstable, feature = "tracing"))]
+    resource_span: tracing::Span,
+    permits_acquired: u32,
+    s: &'a Semaphore,
+    data: *mut T,
 }
 
 impl<'a, T: ?Sized> RwLockWriteGuard<'a, T> {
+    fn skip_drop(self) -> Inner<'a, T> {
+        let me = mem::ManuallyDrop::new(self);
+        // SAFETY: This duplicates the values in every field of the guard, then
+        // forgets the originals, so in the end no value is duplicated.
+        Inner {
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: unsafe { std::ptr::read(&me.resource_span) },
+            permits_acquired: me.permits_acquired,
+            s: me.s,
+            data: me.data,
+        }
+    }
+
     /// Makes a new [`RwLockMappedWriteGuard`] for a component of the locked data.
     ///
     /// This operation cannot fail as the `RwLockWriteGuard` passed in already
@@ -67,19 +90,15 @@ impl<'a, T: ?Sized> RwLockWriteGuard<'a, T> {
         F: FnOnce(&mut T) -> &mut U,
     {
         let data = f(&mut *this) as *mut U;
-        let s = this.s;
-        let permits_acquired = this.permits_acquired;
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = this.resource_span.clone();
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(this);
+        let this = this.skip_drop();
+
         RwLockMappedWriteGuard {
-            permits_acquired,
-            s,
+            permits_acquired: this.permits_acquired,
+            s: this.s,
             data,
-            marker: marker::PhantomData,
+            marker: PhantomData,
             #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
+            resource_span: this.resource_span,
         }
     }
 
@@ -134,19 +153,15 @@ impl<'a, T: ?Sized> RwLockWriteGuard<'a, T> {
             Some(data) => data as *mut U,
             None => return Err(this),
         };
-        let s = this.s;
-        let permits_acquired = this.permits_acquired;
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = this.resource_span.clone();
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(this);
+        let this = this.skip_drop();
+
         Ok(RwLockMappedWriteGuard {
-            permits_acquired,
-            s,
+            permits_acquired: this.permits_acquired,
+            s: this.s,
             data,
-            marker: marker::PhantomData,
+            marker: PhantomData,
             #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
+            resource_span: this.resource_span,
         })
     }
 
@@ -198,12 +213,21 @@ impl<'a, T: ?Sized> RwLockWriteGuard<'a, T> {
     ///
     /// [`RwLock`]: struct@crate::sync::RwLock
     pub fn downgrade(self) -> RwLockReadGuard<'a, T> {
-        let RwLockWriteGuard { s, data, .. } = self;
-        let to_release = (self.permits_acquired - 1) as usize;
+        let this = self.skip_drop();
+        let guard = RwLockReadGuard {
+            s: this.s,
+            data: this.data,
+            marker: PhantomData,
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: this.resource_span,
+        };
+
         // Release all but one of the permits held by the write guard
-        s.release(to_release);
+        let to_release = (this.permits_acquired - 1) as usize;
+        this.s.release(to_release);
+
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        self.resource_span.in_scope(|| {
+        guard.resource_span.in_scope(|| {
             tracing::trace!(
             target: "runtime::resource::state_update",
             write_locked = false,
@@ -212,7 +236,7 @@ impl<'a, T: ?Sized> RwLockWriteGuard<'a, T> {
         });
 
         #[cfg(all(tokio_unstable, feature = "tracing"))]
-        self.resource_span.in_scope(|| {
+        guard.resource_span.in_scope(|| {
             tracing::trace!(
             target: "runtime::resource::state_update",
             current_readers = 1,
@@ -220,18 +244,7 @@ impl<'a, T: ?Sized> RwLockWriteGuard<'a, T> {
             )
         });
 
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = self.resource_span.clone();
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(self);
-
-        RwLockReadGuard {
-            s,
-            data,
-            marker: marker::PhantomData,
-            #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
-        }
+        guard
     }
 }
 
diff --git a/tokio/src/sync/rwlock/write_guard_mapped.rs b/tokio/src/sync/rwlock/write_guard_mapped.rs
index b5c644a9e83..1248c4c7af3 100644
--- a/tokio/src/sync/rwlock/write_guard_mapped.rs
+++ b/tokio/src/sync/rwlock/write_guard_mapped.rs
@@ -1,8 +1,6 @@
 use crate::sync::batch_semaphore::Semaphore;
-use std::fmt;
-use std::marker;
-use std::mem;
-use std::ops;
+use std::marker::PhantomData;
+use std::{fmt, mem, ops};
 
 /// RAII structure used to release the exclusive write access of a lock when
 /// dropped.
@@ -13,16 +11,41 @@ use std::ops;
 ///
 /// [mapping]: method@crate::sync::RwLockWriteGuard::map
 /// [`RwLockWriteGuard`]: struct@crate::sync::RwLockWriteGuard
+#[clippy::has_significant_drop]
 pub struct RwLockMappedWriteGuard<'a, T: ?Sized> {
+    // When changing the fields in this struct, make sure to update the
+    // `skip_drop` method.
     #[cfg(all(tokio_unstable, feature = "tracing"))]
     pub(super) resource_span: tracing::Span,
     pub(super) permits_acquired: u32,
     pub(super) s: &'a Semaphore,
     pub(super) data: *mut T,
-    pub(super) marker: marker::PhantomData<&'a mut T>,
+    pub(super) marker: PhantomData<&'a mut T>,
+}
+
+#[allow(dead_code)] // Unused fields are still used in Drop.
+struct Inner<'a, T: ?Sized> {
+    #[cfg(all(tokio_unstable, feature = "tracing"))]
+    resource_span: tracing::Span,
+    permits_acquired: u32,
+    s: &'a Semaphore,
+    data: *mut T,
 }
 
 impl<'a, T: ?Sized> RwLockMappedWriteGuard<'a, T> {
+    fn skip_drop(self) -> Inner<'a, T> {
+        let me = mem::ManuallyDrop::new(self);
+        // SAFETY: This duplicates the values in every field of the guard, then
+        // forgets the originals, so in the end no value is duplicated.
+        Inner {
+            #[cfg(all(tokio_unstable, feature = "tracing"))]
+            resource_span: unsafe { std::ptr::read(&me.resource_span) },
+            permits_acquired: me.permits_acquired,
+            s: me.s,
+            data: me.data,
+        }
+    }
+
     /// Makes a new `RwLockMappedWriteGuard` for a component of the locked data.
     ///
     /// This operation cannot fail as the `RwLockMappedWriteGuard` passed in already
@@ -64,20 +87,15 @@ impl<'a, T: ?Sized> RwLockMappedWriteGuard<'a, T> {
         F: FnOnce(&mut T) -> &mut U,
     {
         let data = f(&mut *this) as *mut U;
-        let s = this.s;
-        let permits_acquired = this.permits_acquired;
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = this.resource_span.clone();
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(this);
+        let this = this.skip_drop();
 
         RwLockMappedWriteGuard {
-            permits_acquired,
-            s,
+            permits_acquired: this.permits_acquired,
+            s: this.s,
             data,
-            marker: marker::PhantomData,
+            marker: PhantomData,
             #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
+            resource_span: this.resource_span,
         }
     }
 
@@ -131,20 +149,15 @@ impl<'a, T: ?Sized> RwLockMappedWriteGuard<'a, T> {
             Some(data) => data as *mut U,
             None => return Err(this),
         };
-        let s = this.s;
-        let permits_acquired = this.permits_acquired;
-        #[cfg(all(tokio_unstable, feature = "tracing"))]
-        let resource_span = this.resource_span.clone();
-        // NB: Forget to avoid drop impl from being called.
-        mem::forget(this);
+        let this = this.skip_drop();
 
         Ok(RwLockMappedWriteGuard {
-            permits_acquired,
-            s,
+            permits_acquired: this.permits_acquired,
+            s: this.s,
             data,
-            marker: marker::PhantomData,
+            marker: PhantomData,
             #[cfg(all(tokio_unstable, feature = "tracing"))]
-            resource_span,
+            resource_span: this.resource_span,
         })
     }
 }
diff --git a/tokio/src/sync/semaphore.rs b/tokio/src/sync/semaphore.rs
index 6e5a1a88abb..1eee175088e 100644
--- a/tokio/src/sync/semaphore.rs
+++ b/tokio/src/sync/semaphore.rs
@@ -89,6 +89,7 @@ pub struct Semaphore {
 ///
 /// [`acquire`]: crate::sync::Semaphore::acquire()
 #[must_use]
+#[clippy::has_significant_drop]
 #[derive(Debug)]
 pub struct SemaphorePermit<'a> {
     sem: &'a Semaphore,
@@ -101,6 +102,7 @@ pub struct SemaphorePermit<'a> {
 ///
 /// [`acquire_owned`]: crate::sync::Semaphore::acquire_owned()
 #[must_use]
+#[clippy::has_significant_drop]
 #[derive(Debug)]
 pub struct OwnedSemaphorePermit {
     sem: Arc<Semaphore>,
diff --git a/tokio/src/sync/tests/loom_notify.rs b/tokio/src/sync/tests/loom_notify.rs
index d484a758172..a4ded1d35bc 100644
--- a/tokio/src/sync/tests/loom_notify.rs
+++ b/tokio/src/sync/tests/loom_notify.rs
@@ -4,6 +4,11 @@ use loom::future::block_on;
 use loom::sync::Arc;
 use loom::thread;
 
+use tokio_test::{assert_pending, assert_ready};
+
+/// `util::wake_list::NUM_WAKERS`
+const WAKE_LIST_SIZE: usize = 32;
+
 #[test]
 fn notify_one() {
     loom::model(|| {
@@ -138,3 +143,189 @@ fn notify_drop() {
         th2.join().unwrap();
     });
 }
+
+/// Polls two `Notified` futures and checks if poll results are consistent
+/// with each other. If the first future is notified by a `notify_waiters`
+/// call, then the second one must be notified as well.
+#[test]
+fn notify_waiters_poll_consistency() {
+    fn notify_waiters_poll_consistency_variant(poll_setting: [bool; 2]) {
+        let notify = Arc::new(Notify::new());
+        let mut notified = [
+            tokio_test::task::spawn(notify.notified()),
+            tokio_test::task::spawn(notify.notified()),
+        ];
+        for i in 0..2 {
+            if poll_setting[i] {
+                assert_pending!(notified[i].poll());
+            }
+        }
+
+        let tx = notify.clone();
+        let th = thread::spawn(move || {
+            tx.notify_waiters();
+        });
+
+        let res1 = notified[0].poll();
+        let res2 = notified[1].poll();
+
+        // If res1 is ready, then res2 must also be ready.
+        assert!(res1.is_pending() || res2.is_ready());
+
+        th.join().unwrap();
+    }
+
+    // We test different scenarios in which pending futures had or had not
+    // been polled before the call to `notify_waiters`.
+    loom::model(|| notify_waiters_poll_consistency_variant([false, false]));
+    loom::model(|| notify_waiters_poll_consistency_variant([true, false]));
+    loom::model(|| notify_waiters_poll_consistency_variant([false, true]));
+    loom::model(|| notify_waiters_poll_consistency_variant([true, true]));
+}
+
+/// Polls two `Notified` futures and checks if poll results are consistent
+/// with each other. If the first future is notified by a `notify_waiters`
+/// call, then the second one must be notified as well.
+///
+/// Here we also add other `Notified` futures in between to force the two
+/// tested futures to end up in different chunks.
+#[test]
+fn notify_waiters_poll_consistency_many() {
+    fn notify_waiters_poll_consistency_many_variant(order: [usize; 2]) {
+        let notify = Arc::new(Notify::new());
+
+        let mut futs = (0..WAKE_LIST_SIZE + 1)
+            .map(|_| tokio_test::task::spawn(notify.notified()))
+            .collect::<Vec<_>>();
+
+        assert_pending!(futs[order[0]].poll());
+        for i in 2..futs.len() {
+            assert_pending!(futs[i].poll());
+        }
+        assert_pending!(futs[order[1]].poll());
+
+        let tx = notify.clone();
+        let th = thread::spawn(move || {
+            tx.notify_waiters();
+        });
+
+        let res1 = futs[0].poll();
+        let res2 = futs[1].poll();
+
+        // If res1 is ready, then res2 must also be ready.
+        assert!(res1.is_pending() || res2.is_ready());
+
+        th.join().unwrap();
+    }
+
+    // We test different scenarios in which futures are polled in different order.
+    loom::model(|| notify_waiters_poll_consistency_many_variant([0, 1]));
+    loom::model(|| notify_waiters_poll_consistency_many_variant([1, 0]));
+}
+
+/// Checks if a call to `notify_waiters` is observed as atomic when combined
+/// with a concurrent call to `notify_one`.
+#[test]
+fn notify_waiters_is_atomic() {
+    fn notify_waiters_is_atomic_variant(tested_fut_index: usize) {
+        let notify = Arc::new(Notify::new());
+
+        let mut futs = (0..WAKE_LIST_SIZE + 1)
+            .map(|_| tokio_test::task::spawn(notify.notified()))
+            .collect::<Vec<_>>();
+
+        for fut in &mut futs {
+            assert_pending!(fut.poll());
+        }
+
+        let tx = notify.clone();
+        let th = thread::spawn(move || {
+            tx.notify_waiters();
+        });
+
+        block_on(async {
+            // If awaiting one of the futures completes, then we should be
+            // able to assume that all pending futures are notified. Therefore
+            // a notification from a subsequent `notify_one` call should not
+            // be consumed by an old future.
+            futs.remove(tested_fut_index).await;
+
+            let mut new_fut = tokio_test::task::spawn(notify.notified());
+            assert_pending!(new_fut.poll());
+
+            notify.notify_one();
+
+            // `new_fut` must consume the notification from `notify_one`.
+            assert_ready!(new_fut.poll());
+        });
+
+        th.join().unwrap();
+    }
+
+    // We test different scenarios in which the tested future is at the beginning
+    // or at the end of the waiters queue used by `Notify`.
+    loom::model(|| notify_waiters_is_atomic_variant(0));
+    loom::model(|| notify_waiters_is_atomic_variant(32));
+}
+
+/// Checks if a single call to `notify_waiters` does not get through two `Notified`
+/// futures created and awaited sequentially like this:
+/// ```ignore
+/// notify.notified().await;
+/// notify.notified().await;
+/// ```
+#[test]
+fn notify_waiters_sequential_notified_await() {
+    use crate::sync::oneshot;
+
+    loom::model(|| {
+        let notify = Arc::new(Notify::new());
+
+        let (tx_fst, rx_fst) = oneshot::channel();
+        let (tx_snd, rx_snd) = oneshot::channel();
+
+        let receiver = thread::spawn({
+            let notify = notify.clone();
+            move || {
+                block_on(async {
+                    // Poll the first `Notified` to put it as the first waiter
+                    // in the queue.
+                    let mut first_notified = tokio_test::task::spawn(notify.notified());
+                    assert_pending!(first_notified.poll());
+
+                    // Create additional waiters to force `notify_waiters` to
+                    // release the lock at least once.
+                    let _task_pile = (0..WAKE_LIST_SIZE + 1)
+                        .map(|_| {
+                            let mut fut = tokio_test::task::spawn(notify.notified());
+                            assert_pending!(fut.poll());
+                            fut
+                        })
+                        .collect::<Vec<_>>();
+
+                    // We are ready for the notify_waiters call.
+                    tx_fst.send(()).unwrap();
+
+                    first_notified.await;
+
+                    // Poll the second `Notified` future to try to insert
+                    // it to the waiters queue.
+                    let mut second_notified = tokio_test::task::spawn(notify.notified());
+                    assert_pending!(second_notified.poll());
+
+                    // Wait for the `notify_waiters` to end and check if we
+                    // are woken up.
+                    rx_snd.await.unwrap();
+                    assert_pending!(second_notified.poll());
+                });
+            }
+        });
+
+        // Wait for the signal and call `notify_waiters`.
+        block_on(rx_fst).unwrap();
+        notify.notify_waiters();
+        tx_snd.send(()).unwrap();
+
+        receiver.join().unwrap();
+    });
+}
diff --git a/tokio/src/sync/tests/notify.rs b/tokio/src/sync/tests/notify.rs
index eb0da8faad6..4b598959765 100644
--- a/tokio/src/sync/tests/notify.rs
+++ b/tokio/src/sync/tests/notify.rs
@@ -46,6 +46,45 @@ fn notify_clones_waker_before_lock() {
     let _ = future.poll(&mut cx);
 }
 
+#[cfg(panic = "unwind")]
+#[test]
+fn notify_waiters_handles_panicking_waker() {
+    use futures::task::ArcWake;
+
+    let notify = Arc::new(Notify::new());
+
+    struct PanickingWaker(Arc<Notify>);
+
+    impl ArcWake for PanickingWaker {
+        fn wake_by_ref(_arc_self: &Arc<Self>) {
+            panic!("waker panicked");
+        }
+    }
+
+    let bad_fut = notify.notified();
+    pin!(bad_fut);
+
+    let waker = futures::task::waker(Arc::new(PanickingWaker(notify.clone())));
+    let mut cx = Context::from_waker(&waker);
+    let _ = bad_fut.poll(&mut cx);
+
+    let mut futs = Vec::new();
+    for _ in 0..32 {
+        let mut fut = tokio_test::task::spawn(notify.notified());
+        assert!(fut.poll().is_pending());
+        futs.push(fut);
+    }
+
+    assert!(std::panic::catch_unwind(|| {
+        notify.notify_waiters();
+    })
+    .is_err());
+
+    for mut fut in futs {
+        assert!(fut.poll().is_ready());
+    }
+}
+
 #[test]
 fn notify_simple() {
     let notify = Notify::new();
diff --git a/tokio/src/sync/tests/semaphore_batch.rs b/tokio/src/sync/tests/semaphore_batch.rs
index d4e35aa7b2f..c9e9d05ec8f 100644
--- a/tokio/src/sync/tests/semaphore_batch.rs
+++ b/tokio/src/sync/tests/semaphore_batch.rs
@@ -252,3 +252,32 @@ fn cancel_acquire_releases_permits() {
     assert_eq!(6, s.available_permits());
     assert_ok!(s.try_acquire(6));
 }
+
+#[test]
+fn release_permits_at_drop() {
+    use crate::sync::semaphore::*;
+    use futures::task::ArcWake;
+    use std::future::Future;
+    use std::sync::Arc;
+
+    let sem = Arc::new(Semaphore::new(1));
+
+    struct ReleaseOnDrop(Option<OwnedSemaphorePermit>);
+
+    impl ArcWake for ReleaseOnDrop {
+        fn wake_by_ref(_arc_self: &Arc<Self>) {}
+    }
+
+    let mut fut = Box::pin(async {
+        let _permit = sem.acquire().await.unwrap();
+    });
+
+    // Second iteration shouldn't deadlock.
+    for _ in 0..=1 {
+        let waker = futures::task::waker(Arc::new(ReleaseOnDrop(
+            sem.clone().try_acquire_owned().ok(),
+        )));
+        let mut cx = std::task::Context::from_waker(&waker);
+        assert!(fut.as_mut().poll(&mut cx).is_pending());
+    }
+}
diff --git a/tokio/src/sync/watch.rs b/tokio/src/sync/watch.rs
index 6db46b71fc5..4341b642999 100644
--- a/tokio/src/sync/watch.rs
+++ b/tokio/src/sync/watch.rs
@@ -39,6 +39,9 @@
 //! when all [`Receiver`] handles have been dropped. This indicates that there
 //! is no further interest in the values being produced and work can be stopped.
 //!
+//! The value in the channel will not be dropped until the sender and all receivers
+//! have been dropped.
+//!
 //! # Thread safety
 //!
 //! Both [`Sender`] and [`Receiver`] are thread safe. They can be moved to other
@@ -58,6 +61,7 @@ use crate::sync::notify::Notify;
 use crate::loom::sync::atomic::AtomicUsize;
 use crate::loom::sync::atomic::Ordering::Relaxed;
 use crate::loom::sync::{Arc, RwLock, RwLockReadGuard};
+use std::fmt;
 use std::mem;
 use std::ops;
 use std::panic;
@@ -166,7 +170,6 @@ impl<'a, T> Ref<'a, T> {
     }
 }
 
-#[derive(Debug)]
 struct Shared<T> {
     /// The most recent value.
     value: RwLock<T>,
@@ -181,12 +184,24 @@ struct Shared<T> {
     ref_count_rx: AtomicUsize,
 
     /// Notifies waiting receivers that the value changed.
-    notify_rx: Notify,
+    notify_rx: big_notify::BigNotify,
 
     /// Notifies any task listening for `Receiver` dropped events.
     notify_tx: Notify,
 }
 
+impl<T: fmt::Debug> fmt::Debug for Shared<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let state = self.state.load();
+        f.debug_struct("Shared")
+            .field("value", &self.value)
+            .field("version", &state.version())
+            .field("is_closed", &state.is_closed())
+            .field("ref_count_rx", &self.ref_count_rx)
+            .finish()
+    }
+}
+
 pub mod error {
     //! Watch error types.
 
@@ -221,6 +236,62 @@ pub mod error {
     impl std::error::Error for RecvError {}
 }
 
+mod big_notify {
+    use super::*;
+    use crate::sync::notify::Notified;
+
+    // To avoid contention on the lock inside the `Notify`, we store multiple
+    // copies of it. Then, we use either circular access or randomness to spread
+    // out threads over different `Notify` objects.
+    //
+    // Some simple benchmarks show that randomness performs slightly better than
+    // circular access (probably due to contention on `next`), so we prefer to
+    // use randomness when Tokio is compiled with a random number generator.
+    //
+    // When the random number generator is not available, we fall back to
+    // circular access.
+
+    pub(super) struct BigNotify {
+        #[cfg(not(all(not(loom), feature = "sync", any(feature = "rt", feature = "macros"))))]
+        next: AtomicUsize,
+        inner: [Notify; 8],
+    }
+
+    impl BigNotify {
+        pub(super) fn new() -> Self {
+            Self {
+                #[cfg(not(all(
+                    not(loom),
+                    feature = "sync",
+                    any(feature = "rt", feature = "macros")
+                )))]
+                next: AtomicUsize::new(0),
+                inner: Default::default(),
+            }
+        }
+
+        pub(super) fn notify_waiters(&self) {
+            for notify in &self.inner {
+                notify.notify_waiters();
+            }
+        }
+
+        /// This function implements the case where randomness is not available.
+        #[cfg(not(all(not(loom), feature = "sync", any(feature = "rt", feature = "macros"))))]
+        pub(super) fn notified(&self) -> Notified<'_> {
+            let i = self.next.fetch_add(1, Relaxed) % 8;
+            self.inner[i].notified()
+        }
+
+        /// This function implements the case where randomness is available.
+        #[cfg(all(not(loom), feature = "sync", any(feature = "rt", feature = "macros")))]
+        pub(super) fn notified(&self) -> Notified<'_> {
+            let i = crate::runtime::context::thread_rng_n(8) as usize;
+            self.inner[i].notified()
+        }
+    }
+}
+
 use self::state::{AtomicState, Version};
 mod state {
     use crate::loom::sync::atomic::AtomicUsize;
@@ -320,7 +391,7 @@ pub fn channel<T>(init: T) -> (Sender<T>, Receiver<T>) {
         value: RwLock::new(init),
         state: AtomicState::new(),
         ref_count_rx: AtomicUsize::new(1),
-        notify_rx: Notify::new(),
+        notify_rx: big_notify::BigNotify::new(),
         notify_tx: Notify::new(),
     });
 
diff --git a/tokio/src/task/join_set.rs b/tokio/src/task/join_set.rs
index f18130228dc..e6d8d62c3dc 100644
--- a/tokio/src/task/join_set.rs
+++ b/tokio/src/task/join_set.rs
@@ -120,9 +120,9 @@ impl<T: 'static> JoinSet<T> {
     /// Spawn the provided task on the `JoinSet`, returning an [`AbortHandle`]
     /// that can be used to remotely cancel the task.
     ///
-    /// You do not have to `.await` the returned `JoinHandle` to make the
-    /// provided future start execution. It will start running in the background
-    /// immediately when `spawn` is called.
+    /// The provided future will start running in the background immediately
+    /// when this method is called, even if you don't await anything on this
+    /// `JoinSet`.
     ///
     /// # Panics
     ///
@@ -143,9 +143,9 @@ impl<T: 'static> JoinSet<T> {
     /// `JoinSet` returning an [`AbortHandle`] that can be used to remotely
     /// cancel the task.
     ///
-    /// You do not have to `.await` the returned `JoinHandle` to make the
-    /// provided future start execution. It will start running in the background
-    /// immediately when `spawn_on` is called.
+    /// The provided future will start running in the background immediately
+    /// when this method is called, even if you don't await anything on this
+    /// `JoinSet`.
     ///
     /// [`AbortHandle`]: crate::task::AbortHandle
     #[track_caller]
@@ -162,9 +162,9 @@ impl<T: 'static> JoinSet<T> {
     /// `JoinSet`, returning an [`AbortHandle`] that can be used to remotely
     /// cancel the task.
     ///
-    /// You do not have to `.await` the returned `JoinHandle` to make the
-    /// provided future start execution. It will start running in the background
-    /// immediately when `spawn_local` is called.
+    /// The provided future will start running in the background immediately
+    /// when this method is called, even if you don't await anything on this
+    /// `JoinSet`.
     ///
     /// # Panics
     ///
@@ -186,10 +186,8 @@ impl<T: 'static> JoinSet<T> {
     /// remotely cancel the task.
     ///
     /// Unlike the [`spawn_local`] method, this method may be used to spawn local
-    /// tasks when the `LocalSet` is _not_ running. You do not have to `.await`
-    /// the returned `JoinHandle` to make the provided future start execution.
-    /// It will start running immediately whenever the `LocalSet` is next
-    /// started.
+    /// tasks on a `LocalSet` that is _not_ currently running. The provided
+    /// future will start running whenever the `LocalSet` is next started.
     ///
     /// [`LocalSet`]: crate::task::LocalSet
     /// [`AbortHandle`]: crate::task::AbortHandle
diff --git a/tokio/src/task/local.rs b/tokio/src/task/local.rs
index e4a198bd053..b709c215579 100644
--- a/tokio/src/task/local.rs
+++ b/tokio/src/task/local.rs
@@ -1,8 +1,8 @@
 //! Runs `!Send` futures on the current thread.
 use crate::loom::cell::UnsafeCell;
 use crate::loom::sync::{Arc, Mutex};
-use crate::loom::thread::{self, ThreadId};
 use crate::runtime::task::{self, JoinHandle, LocalOwnedTasks, Task};
+use crate::runtime::{context, ThreadId};
 use crate::sync::AtomicWaker;
 use crate::util::RcCell;
 
@@ -34,14 +34,14 @@ cfg_rt! {
     /// async fn main() {
     ///     // `Rc` does not implement `Send`, and thus may not be sent between
     ///     // threads safely.
-    ///     let unsend_data = Rc::new("my unsend data...");
+    ///     let nonsend_data = Rc::new("my nonsend data...");
     ///
-    ///     let unsend_data = unsend_data.clone();
-    ///     // Because the `async` block here moves `unsend_data`, the future is `!Send`.
+    ///     let nonsend_data = nonsend_data.clone();
+    ///     // Because the `async` block here moves `nonsend_data`, the future is `!Send`.
     ///     // Since `tokio::spawn` requires the spawned future to implement `Send`, this
     ///     // will not compile.
     ///     tokio::spawn(async move {
-    ///         println!("{}", unsend_data);
+    ///         println!("{}", nonsend_data);
     ///         // ...
     ///     }).await.unwrap();
     /// }
@@ -60,18 +60,18 @@ cfg_rt! {
     ///
     /// #[tokio::main]
     /// async fn main() {
-    ///     let unsend_data = Rc::new("my unsend data...");
+    ///     let nonsend_data = Rc::new("my nonsend data...");
     ///
     ///     // Construct a local task set that can run `!Send` futures.
     ///     let local = task::LocalSet::new();
     ///
     ///     // Run the local task set.
     ///     local.run_until(async move {
-    ///         let unsend_data = unsend_data.clone();
+    ///         let nonsend_data = nonsend_data.clone();
     ///         // `spawn_local` ensures that the future is spawned on the local
     ///         // task set.
     ///         task::spawn_local(async move {
-    ///             println!("{}", unsend_data);
+    ///             println!("{}", nonsend_data);
     ///             // ...
     ///         }).await.unwrap();
     ///     }).await;
@@ -94,18 +94,18 @@ cfg_rt! {
     ///
     /// #[tokio::main]
     /// async fn main() {
-    ///     let unsend_data = Rc::new("world");
+    ///     let nonsend_data = Rc::new("world");
     ///     let local = task::LocalSet::new();
     ///
-    ///     let unsend_data2 = unsend_data.clone();
+    ///     let nonsend_data2 = nonsend_data.clone();
     ///     local.spawn_local(async move {
     ///         // ...
-    ///         println!("hello {}", unsend_data2)
+    ///         println!("hello {}", nonsend_data2)
     ///     });
     ///
     ///     local.spawn_local(async move {
     ///         time::sleep(time::Duration::from_millis(100)).await;
-    ///         println!("goodbye {}", unsend_data)
+    ///         println!("goodbye {}", nonsend_data)
     ///     });
     ///
     ///     // ...
@@ -277,12 +277,10 @@ pin_project! {
 }
 
 tokio_thread_local!(static CURRENT: LocalData = const { LocalData {
-    thread_id: Cell::new(None),
     ctx: RcCell::new(),
 } });
 
 struct LocalData {
-    thread_id: Cell<Option<ThreadId>>,
     ctx: RcCell<Context>,
 }
 
@@ -291,9 +289,9 @@ cfg_rt! {
     ///
     /// The spawned future will run on the same thread that called `spawn_local`.
     ///
-    /// You do not have to `.await` the returned `JoinHandle` to make the
-    /// provided future start execution. It will start running in the background
-    /// immediately when `spawn_local` is called.
+    /// The provided future will start running in the background immediately
+    /// when `spawn_local` is called, even if you don't await the returned
+    /// `JoinHandle`.
     ///
     /// # Panics
     ///
@@ -311,15 +309,15 @@ cfg_rt! {
     ///
     /// #[tokio::main]
     /// async fn main() {
-    ///     let unsend_data = Rc::new("my unsend data...");
+    ///     let nonsend_data = Rc::new("my nonsend data...");
     ///
     ///     let local = task::LocalSet::new();
     ///
     ///     // Run the local task set.
     ///     local.run_until(async move {
-    ///         let unsend_data = unsend_data.clone();
+    ///         let nonsend_data = nonsend_data.clone();
     ///         task::spawn_local(async move {
-    ///             println!("{}", unsend_data);
+    ///             println!("{}", nonsend_data);
     ///             // ...
     ///         }).await.unwrap();
     ///     }).await;
@@ -379,12 +377,14 @@ impl fmt::Debug for LocalEnterGuard {
 impl LocalSet {
     /// Returns a new local task set.
     pub fn new() -> LocalSet {
+        let owner = context::thread_id().expect("cannot create LocalSet during thread shutdown");
+
         LocalSet {
             tick: Cell::new(0),
             context: Rc::new(Context {
                 shared: Arc::new(Shared {
                     local_state: LocalState {
-                        owner: thread_id().expect("cannot create LocalSet during thread shutdown"),
+                        owner,
                         owned: LocalOwnedTasks::new(),
                         local_queue: UnsafeCell::new(VecDeque::with_capacity(INITIAL_CAPACITY)),
                     },
@@ -417,10 +417,9 @@ impl LocalSet {
     /// This task is guaranteed to be run on the current thread.
     ///
     /// Unlike the free function [`spawn_local`], this method may be used to
-    /// spawn local tasks when the `LocalSet` is _not_ running. You do not have
-    /// to `.await` the returned `JoinHandle` to make the provided future start
-    /// execution. It will start running immediately whenever the `LocalSet` is
-    /// next started.
+    /// spawn local tasks when the `LocalSet` is _not_ running. The provided
+    /// future will start running once the `LocalSet` is next started, even if
+    /// you don't await the returned `JoinHandle`.
     ///
     /// # Examples
     ///
@@ -949,7 +948,7 @@ impl Shared {
 
                 // We are on the thread that owns the `LocalSet`, so we can
                 // wake to the local queue.
-                _ if localdata.get_id() == Some(self.local_state.owner) => {
+                _ if context::thread_id().ok() == Some(self.local_state.owner) => {
                     unsafe {
                         // Safety: we just checked that the thread ID matches
                         // the localset's owner, so this is safe.
@@ -1093,7 +1092,9 @@ impl LocalState {
             // if we couldn't get the thread ID because we're dropping the local
             // data, skip the assertion --- the `Drop` impl is not going to be
             // called from another thread, because `LocalSet` is `!Send`
-            thread_id().map(|id| id == self.owner).unwrap_or(true),
+            context::thread_id()
+                .map(|id| id == self.owner)
+                .unwrap_or(true),
             "`LocalSet`'s local run queue must not be accessed by another thread!"
         );
     }
@@ -1103,26 +1104,6 @@ impl LocalState {
 // ensure they are on the same thread that owns the `LocalSet`.
 unsafe impl Send for LocalState {}
 
-impl LocalData {
-    fn get_id(&self) -> Option<ThreadId> {
-        self.thread_id.get()
-    }
-
-    fn get_or_insert_id(&self) -> ThreadId {
-        self.thread_id.get().unwrap_or_else(|| {
-            let id = thread::current().id();
-            self.thread_id.set(Some(id));
-            id
-        })
-    }
-}
-
-fn thread_id() -> Option<ThreadId> {
-    CURRENT
-        .try_with(|localdata| localdata.get_or_insert_id())
-        .ok()
-}
-
 #[cfg(all(test, not(loom)))]
 mod tests {
     use super::*;
diff --git a/tokio/src/task/spawn.rs b/tokio/src/task/spawn.rs
index 5db11a47994..66b0d673177 100644
--- a/tokio/src/task/spawn.rs
+++ b/tokio/src/task/spawn.rs
@@ -7,9 +7,9 @@ cfg_rt! {
     /// Spawns a new asynchronous task, returning a
     /// [`JoinHandle`](super::JoinHandle) for it.
     ///
-    /// You do not have to `.await` the returned `JoinHandle` to make the
-    /// provided future start execution. It will start running in the background
-    /// immediately when `spawn` is called.
+    /// The provided future will start running in the background immediately
+    /// when `spawn` is called, even if you don't await the returned
+    /// `JoinHandle`.
     ///
     /// Spawning a task enables the task to execute concurrently to other tasks. The
     /// spawned task may execute on the current thread, or it may be sent to a
diff --git a/tokio/src/time/clock.rs b/tokio/src/time/clock.rs
index 0343c4f4cf0..1e273554ec7 100644
--- a/tokio/src/time/clock.rs
+++ b/tokio/src/time/clock.rs
@@ -29,30 +29,40 @@ cfg_not_test_util! {
 
 cfg_test_util! {
     use crate::time::{Duration, Instant};
-    use crate::loom::sync::{Arc, Mutex};
+    use crate::loom::sync::Mutex;
 
     cfg_rt! {
-        fn clock() -> Option<Clock> {
+        #[track_caller]
+        fn with_clock<R>(f: impl FnOnce(Option<&Clock>) -> Result<R, &'static str>) -> R {
             use crate::runtime::Handle;
 
-            match Handle::try_current() {
-                Ok(handle) => Some(handle.inner.driver().clock().clone()),
-                Err(ref e) if e.is_missing_context() => None,
+            let res = match Handle::try_current() {
+                Ok(handle) => f(Some(handle.inner.driver().clock())),
+                Err(ref e) if e.is_missing_context() => f(None),
                 Err(_) => panic!("{}", crate::util::error::THREAD_LOCAL_DESTROYED_ERROR),
+            };
+
+            match res {
+                Ok(ret) => ret,
+                Err(msg) => panic!("{}", msg),
             }
         }
     }
 
     cfg_not_rt! {
-        fn clock() -> Option<Clock> {
-            None
+        #[track_caller]
+        fn with_clock<R>(f: impl FnOnce(Option<&Clock>) -> Result<R, &'static str>) -> R {
+            match f(None) {
+                Ok(ret) => ret,
+                Err(msg) => panic!("{}", msg),
+            }
         }
     }
 
     /// A handle to a source of time.
-    #[derive(Debug, Clone)]
+    #[derive(Debug)]
     pub(crate) struct Clock {
-        inner: Arc<Mutex<Inner>>,
+        inner: Mutex<Inner>,
     }
 
     #[derive(Debug)]
@@ -65,6 +75,9 @@ cfg_test_util! {
 
         /// Instant at which the clock was last unfrozen.
         unfrozen: Option<std::time::Instant>,
+
+        /// Number of `inhibit_auto_advance` calls still in effect.
+        auto_advance_inhibit_count: usize,
     }
 
     /// Pauses time.
@@ -104,8 +117,12 @@ cfg_test_util! {
     /// [`advance`]: crate::time::advance
     #[track_caller]
     pub fn pause() {
-        let clock = clock().expect("time cannot be frozen from outside the Tokio runtime");
-        clock.pause();
+        with_clock(|maybe_clock| {
+            match maybe_clock {
+                Some(clock) => clock.pause(),
+                None => Err("time cannot be frozen from outside the Tokio runtime"),
+            }
+        })
     }
 
     /// Resumes time.
@@ -119,14 +136,21 @@ cfg_test_util! {
     /// runtime.
     #[track_caller]
     pub fn resume() {
-        let clock = clock().expect("time cannot be frozen from outside the Tokio runtime");
-        let mut inner = clock.inner.lock();
+        with_clock(|maybe_clock| {
+            let clock = match maybe_clock {
+                Some(clock) => clock,
+                None => return Err("time cannot be frozen from outside the Tokio runtime"),
+            };
 
-        if inner.unfrozen.is_some() {
-            panic!("time is not frozen");
-        }
+            let mut inner = clock.inner.lock();
+
+            if inner.unfrozen.is_some() {
+                return Err("time is not frozen");
+            }
 
-        inner.unfrozen = Some(std::time::Instant::now());
+            inner.unfrozen = Some(std::time::Instant::now());
+            Ok(())
+        })
     }
 
     /// Advances time.
@@ -161,19 +185,27 @@ cfg_test_util! {
     ///
     /// [`sleep`]: fn@crate::time::sleep
     pub async fn advance(duration: Duration) {
-        let clock = clock().expect("time cannot be frozen from outside the Tokio runtime");
-        clock.advance(duration);
+        with_clock(|maybe_clock| {
+            let clock = match maybe_clock {
+                Some(clock) => clock,
+                None => return Err("time cannot be frozen from outside the Tokio runtime"),
+            };
+
+            clock.advance(duration)
+        });
 
         crate::task::yield_now().await;
     }
 
     /// Returns the current instant, factoring in frozen time.
     pub(crate) fn now() -> Instant {
-        if let Some(clock) = clock() {
-            clock.now()
-        } else {
-            Instant::from_std(std::time::Instant::now())
-        }
+        with_clock(|maybe_clock| {
+            Ok(if let Some(clock) = maybe_clock {
+                clock.now()
+            } else {
+                Instant::from_std(std::time::Instant::now())
+            })
+        })
     }
 
     impl Clock {
@@ -183,49 +215,67 @@ cfg_test_util! {
             let now = std::time::Instant::now();
 
             let clock = Clock {
-                inner: Arc::new(Mutex::new(Inner {
+                inner: Mutex::new(Inner {
                     enable_pausing,
                     base: now,
                     unfrozen: Some(now),
-                })),
+                    auto_advance_inhibit_count: 0,
+                }),
             };
 
             if start_paused {
-                clock.pause();
+                if let Err(msg) = clock.pause() {
+                    panic!("{}", msg);
+                }
             }
 
             clock
         }
 
-        #[track_caller]
-        pub(crate) fn pause(&self) {
+        pub(crate) fn pause(&self) -> Result<(), &'static str> {
             let mut inner = self.inner.lock();
 
             if !inner.enable_pausing {
                 drop(inner); // avoid poisoning the lock
-                panic!("`time::pause()` requires the `current_thread` Tokio runtime. \
+                return Err("`time::pause()` requires the `current_thread` Tokio runtime. \
                         This is the default Runtime used by `#[tokio::test].");
             }
 
-            let elapsed = inner.unfrozen.as_ref().expect("time is already frozen").elapsed();
+            let elapsed = match inner.unfrozen.as_ref() {
+                Some(v) => v.elapsed(),
+                None => return Err("time is already frozen")
+            };
             inner.base += elapsed;
             inner.unfrozen = None;
+
+            Ok(())
         }
 
-        pub(crate) fn is_paused(&self) -> bool {
+        /// Temporarily stop auto-advancing the clock (see `tokio::time::pause`).
+        pub(crate) fn inhibit_auto_advance(&self) {
+            let mut inner = self.inner.lock();
+            inner.auto_advance_inhibit_count += 1;
+        }
+
+        pub(crate) fn allow_auto_advance(&self) {
+            let mut inner = self.inner.lock();
+            inner.auto_advance_inhibit_count -= 1;
+        }
+
+        pub(crate) fn can_auto_advance(&self) -> bool {
             let inner = self.inner.lock();
-            inner.unfrozen.is_none()
+            inner.unfrozen.is_none() && inner.auto_advance_inhibit_count == 0
         }
 
-        #[track_caller]
-        pub(crate) fn advance(&self, duration: Duration) {
+        pub(crate) fn advance(&self, duration: Duration) -> Result<(), &'static str> {
             let mut inner = self.inner.lock();
 
             if inner.unfrozen.is_some() {
-                panic!("time is not frozen");
+                return Err("time is not frozen");
             }
 
             inner.base += duration;
+            Ok(())
         }
 
         pub(crate) fn now(&self) -> Instant {
diff --git a/tokio/src/time/sleep.rs b/tokio/src/time/sleep.rs
index d974e1ab282..370a98b9902 100644
--- a/tokio/src/time/sleep.rs
+++ b/tokio/src/time/sleep.rs
@@ -235,7 +235,6 @@ pin_project! {
 cfg_trace! {
     #[derive(Debug)]
     struct Inner {
-        deadline: Instant,
         ctx: trace::AsyncOpTracingCtx,
     }
 }
@@ -243,7 +242,6 @@ cfg_trace! {
 cfg_not_trace! {
     #[derive(Debug)]
     struct Inner {
-        deadline: Instant,
     }
 }
 
@@ -261,10 +259,11 @@ impl Sleep {
 
         #[cfg(all(tokio_unstable, feature = "tracing"))]
         let inner = {
+            let clock = handle.driver().clock();
             let handle = &handle.driver().time();
             let time_source = handle.time_source();
             let deadline_tick = time_source.deadline_to_tick(deadline);
-            let duration = deadline_tick.saturating_sub(time_source.now());
+            let duration = deadline_tick.saturating_sub(time_source.now(clock));
 
             let location = location.expect("should have location if tracing");
             let resource_span = tracing::trace_span!(
@@ -296,11 +295,11 @@ impl Sleep {
                 resource_span,
             };
 
-            Inner { deadline, ctx }
+            Inner { ctx }
         };
 
         #[cfg(not(all(tokio_unstable, feature = "tracing")))]
-        let inner = Inner { deadline };
+        let inner = Inner {};
 
         Sleep { inner, entry }
     }
@@ -311,7 +310,7 @@ impl Sleep {
 
     /// Returns the instant at which the future will complete.
     pub fn deadline(&self) -> Instant {
-        self.inner.deadline
+        self.entry.deadline()
     }
 
     /// Returns `true` if `Sleep` has elapsed.
@@ -357,7 +356,6 @@ impl Sleep {
     fn reset_inner(self: Pin<&mut Self>, deadline: Instant) {
         let mut me = self.project();
         me.entry.as_mut().reset(deadline);
-        (*me.inner).deadline = deadline;
 
         #[cfg(all(tokio_unstable, feature = "tracing"))]
         {
@@ -370,8 +368,9 @@ impl Sleep {
                 tracing::trace_span!("runtime.resource.async_op.poll");
 
             let duration = {
+                let clock = me.entry.clock();
                 let time_source = me.entry.driver().time_source();
-                let now = time_source.now();
+                let now = time_source.now(clock);
                 let deadline_tick = time_source.deadline_to_tick(deadline);
                 deadline_tick.saturating_sub(now)
             };
diff --git a/tokio/src/time/timeout.rs b/tokio/src/time/timeout.rs
index 3bb98ea6f92..b6837360edc 100644
--- a/tokio/src/time/timeout.rs
+++ b/tokio/src/time/timeout.rs
@@ -28,6 +28,11 @@ use std::task::{self, Poll};
 /// This function returns a future whose return type is [`Result`]`<T,`[`Elapsed`]`>`, where `T` is the
 /// return type of the provided future.
 ///
+/// If the provided future completes immediatelly, then the future returned from
+/// this function is guaranteed to complete immediatelly with an [`Ok`] variant
+/// no matter the provided duration.
+///
+/// [`Ok`]: std::result::Result::Ok
 /// [`Result`]: std::result::Result
 /// [`Elapsed`]: crate::time::error::Elapsed
 ///
@@ -100,6 +105,11 @@ where
 /// This function returns a future whose return type is [`Result`]`<T,`[`Elapsed`]`>`, where `T` is the
 /// return type of the provided future.
 ///
+/// If the provided future completes immediatelly, then the future returned from
+/// this function is guaranteed to complete immediatelly with an [`Ok`] variant
+/// no matter the provided deadline.
+///
+/// [`Ok`]: std::result::Result::Ok
 /// [`Result`]: std::result::Result
 /// [`Elapsed`]: crate::time::error::Elapsed
 ///
diff --git a/tokio/src/util/linked_list.rs b/tokio/src/util/linked_list.rs
index 9698f727f4f..460e2564d4e 100644
--- a/tokio/src/util/linked_list.rs
+++ b/tokio/src/util/linked_list.rs
@@ -126,7 +126,7 @@ impl<L: Link> LinkedList<L, L::Target> {
     pub(crate) fn push_front(&mut self, val: L::Handle) {
         // The value should not be dropped, it is being inserted into the list
         let val = ManuallyDrop::new(val);
-        let ptr = L::as_raw(&*val);
+        let ptr = L::as_raw(&val);
         assert_ne!(self.head, Some(ptr));
         unsafe {
             L::pointers(ptr).as_mut().set_next(self.head);
@@ -178,8 +178,12 @@ impl<L: Link> LinkedList<L, L::Target> {
     ///
     /// # Safety
     ///
-    /// The caller **must** ensure that `node` is currently contained by
-    /// `self` or not contained by any other list.
+    /// The caller **must** ensure that exactly one of the following is true:
+    /// - `node` is currently contained by `self`,
+    /// - `node` is not contained by any list,
+    /// - `node` is currently contained by some other `GuardedLinkedList` **and**
+    ///   the caller has an exclusive access to that list. This condition is
+    ///   used by the linked list in `sync::Notify`.
     pub(crate) unsafe fn remove(&mut self, node: NonNull<L::Target>) -> Option<L::Handle> {
         if let Some(prev) = L::pointers(node).as_ref().get_prev() {
             debug_assert_eq!(L::pointers(prev).as_ref().get_next(), Some(node));
@@ -290,6 +294,96 @@ cfg_io_readiness! {
     }
 }
 
+// ===== impl GuardedLinkedList =====
+
+feature! {
+    #![any(
+        feature = "process",
+        feature = "sync",
+        feature = "rt",
+        feature = "signal",
+    )]
+
+    /// An intrusive linked list, but instead of keeping pointers to the head
+    /// and tail nodes, it uses a special guard node linked with those nodes.
+    /// It means that the list is circular and every pointer of a node from
+    /// the list is not `None`, including pointers from the guard node.
+    ///
+    /// If a list is empty, then both pointers of the guard node are pointing
+    /// at the guard node itself.
+    pub(crate) struct GuardedLinkedList<L, T> {
+        /// Pointer to the guard node.
+        guard: NonNull<T>,
+
+        /// Node type marker.
+        _marker: PhantomData<*const L>,
+    }
+
+    impl<U, L: Link<Handle = NonNull<U>>> LinkedList<L, L::Target> {
+        /// Turns a linked list into the guarded version by linking the guard node
+        /// with the head and tail nodes. Like with other nodes, you should guarantee
+        /// that the guard node is pinned in memory.
+        pub(crate) fn into_guarded(self, guard_handle: L::Handle) -> GuardedLinkedList<L, L::Target> {
+            // `guard_handle` is a NonNull pointer, we don't have to care about dropping it.
+            let guard = L::as_raw(&guard_handle);
+
+            unsafe {
+                if let Some(head) = self.head {
+                    debug_assert!(L::pointers(head).as_ref().get_prev().is_none());
+                    L::pointers(head).as_mut().set_prev(Some(guard));
+                    L::pointers(guard).as_mut().set_next(Some(head));
+
+                    // The list is not empty, so the tail cannot be `None`.
+                    let tail = self.tail.unwrap();
+                    debug_assert!(L::pointers(tail).as_ref().get_next().is_none());
+                    L::pointers(tail).as_mut().set_next(Some(guard));
+                    L::pointers(guard).as_mut().set_prev(Some(tail));
+                } else {
+                    // The list is empty.
+                    L::pointers(guard).as_mut().set_prev(Some(guard));
+                    L::pointers(guard).as_mut().set_next(Some(guard));
+                }
+            }
+
+            GuardedLinkedList { guard, _marker: PhantomData }
+        }
+    }
+
+    impl<L: Link> GuardedLinkedList<L, L::Target> {
+        fn tail(&self) -> Option<NonNull<L::Target>> {
+            let tail_ptr = unsafe {
+                L::pointers(self.guard).as_ref().get_prev().unwrap()
+            };
+
+            // Compare the tail pointer with the address of the guard node itself.
+            // If the guard points at itself, then there are no other nodes and
+            // the list is considered empty.
+            if tail_ptr != self.guard {
+                Some(tail_ptr)
+            } else {
+                None
+            }
+        }
+
+        /// Removes the last element from a list and returns it, or None if it is
+        /// empty.
+        pub(crate) fn pop_back(&mut self) -> Option<L::Handle> {
+            unsafe {
+                let last = self.tail()?;
+                let before_last = L::pointers(last).as_ref().get_prev().unwrap();
+
+                L::pointers(self.guard).as_mut().set_prev(Some(before_last));
+                L::pointers(before_last).as_mut().set_next(Some(self.guard));
+
+                L::pointers(last).as_mut().set_prev(None);
+                L::pointers(last).as_mut().set_next(None);
+
+                Some(L::from_raw(last))
+            }
+        }
+    }
+}
+
 // ===== impl Pointers =====
 
 impl<T> Pointers<T> {
@@ -352,9 +446,9 @@ impl<T> fmt::Debug for Pointers<T> {
     }
 }
 
-#[cfg(test)]
+#[cfg(any(test, fuzzing))]
 #[cfg(not(loom))]
-mod tests {
+pub(crate) mod tests {
     use super::*;
 
     use std::pin::Pin;
@@ -623,31 +717,21 @@ mod tests {
         }
     }
 
-    #[cfg(not(tokio_wasm))]
-    proptest::proptest! {
-        #[test]
-        fn fuzz_linked_list(ops: Vec<usize>) {
-            run_fuzz(ops);
-        }
-    }
-
-    #[cfg(not(tokio_wasm))]
-    fn run_fuzz(ops: Vec<usize>) {
-        use std::collections::VecDeque;
-
-        #[derive(Debug)]
+    #[cfg(fuzzing)]
+    pub fn fuzz_linked_list(ops: &[u8]) {
         enum Op {
             Push,
             Pop,
             Remove(usize),
         }
+        use std::collections::VecDeque;
 
         let ops = ops
             .iter()
-            .map(|i| match i % 3 {
+            .map(|i| match i % 3u8 {
                 0 => Op::Push,
                 1 => Op::Pop,
-                2 => Op::Remove(i / 3),
+                2 => Op::Remove((i / 3u8) as usize),
                 _ => unreachable!(),
             })
             .collect::<Vec<_>>();
diff --git a/tokio/src/util/mod.rs b/tokio/src/util/mod.rs
index 245e64de6b4..9f6119acbb5 100644
--- a/tokio/src/util/mod.rs
+++ b/tokio/src/util/mod.rs
@@ -6,7 +6,12 @@ cfg_io_driver! {
 #[cfg(feature = "rt")]
 pub(crate) mod atomic_cell;
 
-#[cfg(any(feature = "rt", feature = "signal", feature = "process"))]
+#[cfg(any(
+    feature = "rt",
+    feature = "signal",
+    feature = "process",
+    tokio_no_const_mutex_new,
+))]
 pub(crate) mod once_cell;
 
 #[cfg(any(
diff --git a/tokio/src/util/once_cell.rs b/tokio/src/util/once_cell.rs
index 138d2a74626..1925f0a7606 100644
--- a/tokio/src/util/once_cell.rs
+++ b/tokio/src/util/once_cell.rs
@@ -25,7 +25,7 @@ impl<T> OnceCell<T> {
     /// If the `init` closure panics, then the `OnceCell` is poisoned and all
     /// future calls to `get` will panic.
     #[inline]
-    pub(crate) fn get(&self, init: fn() -> T) -> &T {
+    pub(crate) fn get(&self, init: impl FnOnce() -> T) -> &T {
         if !self.once.is_completed() {
             self.do_init(init);
         }
@@ -41,7 +41,7 @@ impl<T> OnceCell<T> {
     }
 
     #[cold]
-    fn do_init(&self, init: fn() -> T) {
+    fn do_init(&self, init: impl FnOnce() -> T) {
         let value_ptr = self.value.get() as *mut T;
 
         self.once.call_once(|| {
diff --git a/tokio/src/util/pad.rs b/tokio/src/util/pad.rs
deleted file mode 100644
index bf0913ca853..00000000000
--- a/tokio/src/util/pad.rs
+++ /dev/null
@@ -1,52 +0,0 @@
-use core::fmt;
-use core::ops::{Deref, DerefMut};
-
-#[derive(Clone, Copy, Default, Hash, PartialEq, Eq)]
-// Starting from Intel's Sandy Bridge, spatial prefetcher is now pulling pairs of 64-byte cache
-// lines at a time, so we have to align to 128 bytes rather than 64.
-//
-// Sources:
-// - https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-optimization-manual.pdf
-// - https://github.com/facebook/folly/blob/1b5288e6eea6df074758f877c849b6e73bbb9fbb/folly/lang/Align.h#L107
-#[cfg_attr(target_arch = "x86_64", repr(align(128)))]
-#[cfg_attr(not(target_arch = "x86_64"), repr(align(64)))]
-pub(crate) struct CachePadded<T> {
-    value: T,
-}
-
-unsafe impl<T: Send> Send for CachePadded<T> {}
-unsafe impl<T: Sync> Sync for CachePadded<T> {}
-
-impl<T> CachePadded<T> {
-    pub(crate) fn new(t: T) -> CachePadded<T> {
-        CachePadded::<T> { value: t }
-    }
-}
-
-impl<T> Deref for CachePadded<T> {
-    type Target = T;
-
-    fn deref(&self) -> &T {
-        &self.value
-    }
-}
-
-impl<T> DerefMut for CachePadded<T> {
-    fn deref_mut(&mut self) -> &mut T {
-        &mut self.value
-    }
-}
-
-impl<T: fmt::Debug> fmt::Debug for CachePadded<T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("CachePadded")
-            .field("value", &self.value)
-            .finish()
-    }
-}
-
-impl<T> From<T> for CachePadded<T> {
-    fn from(t: T) -> Self {
-        CachePadded::new(t)
-    }
-}
diff --git a/tokio/src/util/rand.rs b/tokio/src/util/rand.rs
index 749da6bcac4..7018c1ee0e5 100644
--- a/tokio/src/util/rand.rs
+++ b/tokio/src/util/rand.rs
@@ -135,7 +135,11 @@ impl FastRand {
         old_seed
     }
 
-    #[cfg(any(feature = "macros", feature = "rt-multi-thread"))]
+    #[cfg(any(
+        feature = "macros",
+        feature = "rt-multi-thread",
+        all(feature = "sync", feature = "rt")
+    ))]
     pub(crate) fn fastrand_n(&self, n: u32) -> u32 {
         // This is similar to fastrand() % n, but faster.
         // See https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/
diff --git a/tokio/tests/_require_full.rs b/tokio/tests/_require_full.rs
index a339374fd86..4b9698afedd 100644
--- a/tokio/tests/_require_full.rs
+++ b/tokio/tests/_require_full.rs
@@ -1,2 +1,8 @@
-#![cfg(not(any(feature = "full", tokio_wasm)))]
+#[cfg(not(any(feature = "full", tokio_wasm)))]
 compile_error!("run main Tokio tests with `--features full`");
+
+// CI sets `--cfg tokio_no_parking_lot` when trying to run tests with
+// `parking_lot` disabled. This check prevents "silent failure" if `parking_lot`
+// accidentally gets enabled.
+#[cfg(all(tokio_no_parking_lot, feature = "parking_lot"))]
+compile_error!("parking_lot feature enabled when it should not be");
diff --git a/tokio/tests/async_send_sync.rs b/tokio/tests/async_send_sync.rs
index e46d5c85a8f..0c2c34a0796 100644
--- a/tokio/tests/async_send_sync.rs
+++ b/tokio/tests/async_send_sync.rs
@@ -263,6 +263,19 @@ mod unix_datagram {
     async_assert_fn!(UnixStream::writable(_): Send & Sync & !Unpin);
 }
 
+#[cfg(unix)]
+mod unix_pipe {
+    use super::*;
+    use tokio::net::unix::pipe::*;
+    assert_value!(OpenOptions: Send & Sync & Unpin);
+    assert_value!(Receiver: Send & Sync & Unpin);
+    assert_value!(Sender: Send & Sync & Unpin);
+    async_assert_fn!(Receiver::readable(_): Send & Sync & !Unpin);
+    async_assert_fn!(Receiver::ready(_, tokio::io::Interest): Send & Sync & !Unpin);
+    async_assert_fn!(Sender::ready(_, tokio::io::Interest): Send & Sync & !Unpin);
+    async_assert_fn!(Sender::writable(_): Send & Sync & !Unpin);
+}
+
 #[cfg(windows)]
 mod windows_named_pipe {
     use super::*;
@@ -334,6 +347,15 @@ assert_value!(tokio::sync::OnceCell<YY>: Send & Sync & Unpin);
 assert_value!(tokio::sync::OwnedMutexGuard<NN>: !Send & !Sync & Unpin);
 assert_value!(tokio::sync::OwnedMutexGuard<YN>: Send & !Sync & Unpin);
 assert_value!(tokio::sync::OwnedMutexGuard<YY>: Send & Sync & Unpin);
+assert_value!(tokio::sync::OwnedMappedMutexGuard<NN,NN>: !Send & !Sync & Unpin);
+assert_value!(tokio::sync::OwnedMappedMutexGuard<NN,YN>: !Send & !Sync & Unpin);
+assert_value!(tokio::sync::OwnedMappedMutexGuard<NN,YY>: !Send & !Sync & Unpin);
+assert_value!(tokio::sync::OwnedMappedMutexGuard<YN,NN>: !Send & !Sync & Unpin);
+assert_value!(tokio::sync::OwnedMappedMutexGuard<YN,YN>: Send & !Sync & Unpin);
+assert_value!(tokio::sync::OwnedMappedMutexGuard<YN,YY>: Send & !Sync & Unpin);
+assert_value!(tokio::sync::OwnedMappedMutexGuard<YY,NN>: !Send & !Sync & Unpin);
+assert_value!(tokio::sync::OwnedMappedMutexGuard<YY,YN>: Send & !Sync & Unpin);
+assert_value!(tokio::sync::OwnedMappedMutexGuard<YY,YY>: Send & Sync & Unpin);
 assert_value!(tokio::sync::OwnedRwLockMappedWriteGuard<NN>: !Send & !Sync & Unpin);
 assert_value!(tokio::sync::OwnedRwLockMappedWriteGuard<YN>: !Send & !Sync & Unpin);
 assert_value!(tokio::sync::OwnedRwLockMappedWriteGuard<YY>: Send & Sync & Unpin);
diff --git a/tokio/tests/buffered.rs b/tokio/tests/buffered.rs
index 19afebd392a..4251c3fcc0b 100644
--- a/tokio/tests/buffered.rs
+++ b/tokio/tests/buffered.rs
@@ -18,10 +18,10 @@ async fn echo_server() {
     let msg = "foo bar baz";
 
     let t = thread::spawn(move || {
-        let mut s = assert_ok!(TcpStream::connect(&addr));
+        let mut s = assert_ok!(TcpStream::connect(addr));
 
         let t2 = thread::spawn(move || {
-            let mut s = assert_ok!(TcpStream::connect(&addr));
+            let mut s = assert_ok!(TcpStream::connect(addr));
             let mut b = vec![0; msg.len() * N];
             assert_ok!(s.read_exact(&mut b));
             b
diff --git a/tokio/tests/fs_canonicalize_dir.rs b/tokio/tests/fs_canonicalize_dir.rs
new file mode 100644
index 00000000000..83f0d813737
--- /dev/null
+++ b/tokio/tests/fs_canonicalize_dir.rs
@@ -0,0 +1,22 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // WASI does not support all fs operations
+
+use tokio::fs;
+
+#[tokio::test]
+#[cfg(unix)]
+async fn canonicalize_root_dir_unix() {
+    assert_eq!(fs::canonicalize("/.").await.unwrap().to_str().unwrap(), "/");
+}
+
+#[tokio::test]
+#[cfg(windows)]
+async fn canonicalize_root_dir_windows() {
+    // 2-step let bindings due to Rust memory semantics
+    let dir_path = fs::canonicalize("C:\\.\\").await.unwrap();
+
+    let dir_name = dir_path.to_str().unwrap();
+
+    assert!(dir_name.starts_with("\\\\"));
+    assert!(dir_name.ends_with("C:\\"));
+}
diff --git a/tokio/tests/fs_copy.rs b/tokio/tests/fs_copy.rs
index 04678cf05b4..e6e5b666f4a 100644
--- a/tokio/tests/fs_copy.rs
+++ b/tokio/tests/fs_copy.rs
@@ -1,5 +1,5 @@
 #![warn(rust_2018_idioms)]
-#![cfg(all(feature = "full", not(tokio_wasi)))] // Wasi does not support file operations
+#![cfg(all(feature = "full", not(tokio_wasi)))] // WASI does not support all fs operations
 
 use tempfile::tempdir;
 use tokio::fs;
diff --git a/tokio/tests/fs_dir.rs b/tokio/tests/fs_dir.rs
index f197a40ac95..5f653cb2135 100644
--- a/tokio/tests/fs_dir.rs
+++ b/tokio/tests/fs_dir.rs
@@ -1,5 +1,5 @@
 #![warn(rust_2018_idioms)]
-#![cfg(all(feature = "full", not(tokio_wasi)))] // Wasi does not support directory operations
+#![cfg(all(feature = "full", not(tokio_wasi)))] // WASI does not support all fs operations
 
 use tokio::fs;
 use tokio_test::{assert_err, assert_ok};
@@ -45,6 +45,27 @@ async fn build_dir() {
     );
 }
 
+#[tokio::test]
+#[cfg(unix)]
+async fn build_dir_mode_read_only() {
+    let base_dir = tempdir().unwrap();
+    let new_dir = base_dir.path().join("abc");
+
+    assert_ok!(
+        fs::DirBuilder::new()
+            .recursive(true)
+            .mode(0o444)
+            .create(&new_dir)
+            .await
+    );
+
+    assert!(fs::metadata(new_dir)
+        .await
+        .expect("metadata result")
+        .permissions()
+        .readonly());
+}
+
 #[tokio::test]
 async fn remove() {
     let base_dir = tempdir().unwrap();
@@ -85,3 +106,21 @@ async fn read_inherent() {
         vec!["aa".to_string(), "bb".to_string(), "cc".to_string()]
     );
 }
+
+#[tokio::test]
+async fn read_dir_entry_info() {
+    let temp_dir = tempdir().unwrap();
+
+    let file_path = temp_dir.path().join("a.txt");
+
+    fs::write(&file_path, b"Hello File!").await.unwrap();
+
+    let mut dir = fs::read_dir(temp_dir.path()).await.unwrap();
+
+    let first_entry = dir.next_entry().await.unwrap().unwrap();
+
+    assert_eq!(first_entry.path(), file_path);
+    assert_eq!(first_entry.file_name(), "a.txt");
+    assert!(first_entry.metadata().await.unwrap().is_file());
+    assert!(first_entry.file_type().await.unwrap().is_file());
+}
diff --git a/tokio/tests/fs_file.rs b/tokio/tests/fs_file.rs
index 603ccad3802..dde09906246 100644
--- a/tokio/tests/fs_file.rs
+++ b/tokio/tests/fs_file.rs
@@ -1,5 +1,5 @@
 #![warn(rust_2018_idioms)]
-#![cfg(all(feature = "full", not(tokio_wasi)))] // Wasi does not support file operations
+#![cfg(all(feature = "full", not(tokio_wasi)))] // WASI does not support all fs operations
 
 use std::io::prelude::*;
 use tempfile::NamedTempFile;
@@ -87,13 +87,93 @@ async fn coop() {
     panic!("did not yield");
 }
 
+#[tokio::test]
+async fn write_to_clone() {
+    let tempfile = tempfile();
+
+    let file = File::create(tempfile.path()).await.unwrap();
+    let mut clone = file.try_clone().await.unwrap();
+
+    clone.write_all(HELLO).await.unwrap();
+    clone.flush().await.unwrap();
+
+    let contents = std::fs::read(tempfile.path()).unwrap();
+    assert_eq!(contents, HELLO);
+}
+
+#[tokio::test]
+async fn write_into_std() {
+    let tempfile = tempfile();
+
+    let file = File::create(tempfile.path()).await.unwrap();
+    let mut std_file = file.into_std().await;
+
+    std_file.write_all(HELLO).unwrap();
+
+    let contents = std::fs::read(tempfile.path()).unwrap();
+    assert_eq!(contents, HELLO);
+}
+
+#[tokio::test]
+async fn write_into_std_immediate() {
+    let tempfile = tempfile();
+
+    let file = File::create(tempfile.path()).await.unwrap();
+    let mut std_file = file.try_into_std().unwrap();
+
+    std_file.write_all(HELLO).unwrap();
+
+    let contents = std::fs::read(tempfile.path()).unwrap();
+    assert_eq!(contents, HELLO);
+}
+
+#[tokio::test]
+async fn read_file_from_std() {
+    let mut tempfile = tempfile();
+    tempfile.write_all(HELLO).unwrap();
+
+    let std_file = std::fs::File::open(tempfile.path()).unwrap();
+    let mut file = File::from(std_file);
+
+    let mut buf = [0; 1024];
+    let n = file.read(&mut buf).await.unwrap();
+    assert_eq!(n, HELLO.len());
+    assert_eq!(&buf[..n], HELLO);
+}
+
 fn tempfile() -> NamedTempFile {
     NamedTempFile::new().unwrap()
 }
 
 #[tokio::test]
 #[cfg(unix)]
-async fn unix_fd() {
+async fn file_debug_fmt() {
+    let tempfile = tempfile();
+
+    let file = File::open(tempfile.path()).await.unwrap();
+
+    assert_eq!(
+        &format!("{:?}", file)[0..33],
+        "tokio::fs::File { std: File { fd:"
+    );
+}
+
+#[tokio::test]
+#[cfg(windows)]
+async fn file_debug_fmt() {
+    let tempfile = tempfile();
+
+    let file = File::open(tempfile.path()).await.unwrap();
+
+    assert_eq!(
+        &format!("{:?}", file)[0..37],
+        "tokio::fs::File { std: File { handle:"
+    );
+}
+
+#[tokio::test]
+#[cfg(unix)]
+async fn unix_fd_is_valid() {
     use std::os::unix::io::AsRawFd;
     let tempfile = tempfile();
 
@@ -101,6 +181,27 @@ async fn unix_fd() {
     assert!(file.as_raw_fd() as u64 > 0);
 }
 
+#[tokio::test]
+#[cfg(unix)]
+async fn read_file_from_unix_fd() {
+    use std::os::unix::io::AsRawFd;
+    use std::os::unix::io::FromRawFd;
+
+    let mut tempfile = tempfile();
+    tempfile.write_all(HELLO).unwrap();
+
+    let file1 = File::open(tempfile.path()).await.unwrap();
+    let raw_fd = file1.as_raw_fd();
+    assert!(raw_fd > 0);
+
+    let mut file2 = unsafe { File::from_raw_fd(raw_fd) };
+
+    let mut buf = [0; 1024];
+    let n = file2.read(&mut buf).await.unwrap();
+    assert_eq!(n, HELLO.len());
+    assert_eq!(&buf[..n], HELLO);
+}
+
 #[tokio::test]
 #[cfg(windows)]
 async fn windows_handle() {
diff --git a/tokio/tests/fs_link.rs b/tokio/tests/fs_link.rs
index d198abc5182..681b566607e 100644
--- a/tokio/tests/fs_link.rs
+++ b/tokio/tests/fs_link.rs
@@ -1,10 +1,9 @@
 #![warn(rust_2018_idioms)]
-#![cfg(all(feature = "full", not(tokio_wasi)))] // Wasi does not support file operations
+#![cfg(all(feature = "full", not(tokio_wasi)))] // WASI does not support all fs operations
 
 use tokio::fs;
 
-use std::io::prelude::*;
-use std::io::BufReader;
+use std::io::Write;
 use tempfile::tempdir;
 
 #[tokio::test]
@@ -13,24 +12,23 @@ async fn test_hard_link() {
     let src = dir.path().join("src.txt");
     let dst = dir.path().join("dst.txt");
 
-    {
-        let mut file = std::fs::File::create(&src).unwrap();
-        file.write_all(b"hello").unwrap();
-    }
+    std::fs::File::create(&src)
+        .unwrap()
+        .write_all(b"hello")
+        .unwrap();
 
-    let dst_2 = dst.clone();
+    fs::hard_link(&src, &dst).await.unwrap();
 
-    assert!(fs::hard_link(src, dst_2.clone()).await.is_ok());
+    std::fs::File::create(&src)
+        .unwrap()
+        .write_all(b"new-data")
+        .unwrap();
 
-    let mut content = String::new();
+    let content = fs::read(&dst).await.unwrap();
+    assert_eq!(content, b"new-data");
 
-    {
-        let file = std::fs::File::open(dst).unwrap();
-        let mut reader = BufReader::new(file);
-        reader.read_to_string(&mut content).unwrap();
-    }
-
-    assert!(content == "hello");
+    // test that this is not a symlink:
+    assert!(fs::read_link(&dst).await.is_err());
 }
 
 #[cfg(unix)]
@@ -40,25 +38,20 @@ async fn test_symlink() {
     let src = dir.path().join("src.txt");
     let dst = dir.path().join("dst.txt");
 
-    {
-        let mut file = std::fs::File::create(&src).unwrap();
-        file.write_all(b"hello").unwrap();
-    }
-
-    let src_2 = src.clone();
-    let dst_2 = dst.clone();
-
-    assert!(fs::symlink(src_2.clone(), dst_2.clone()).await.is_ok());
+    std::fs::File::create(&src)
+        .unwrap()
+        .write_all(b"hello")
+        .unwrap();
 
-    let mut content = String::new();
+    fs::symlink(&src, &dst).await.unwrap();
 
-    {
-        let file = std::fs::File::open(dst.clone()).unwrap();
-        let mut reader = BufReader::new(file);
-        reader.read_to_string(&mut content).unwrap();
-    }
+    std::fs::File::create(&src)
+        .unwrap()
+        .write_all(b"new-data")
+        .unwrap();
 
-    assert!(content == "hello");
+    let content = fs::read(&dst).await.unwrap();
+    assert_eq!(content, b"new-data");
 
     let read = fs::read_link(dst.clone()).await.unwrap();
     assert!(read == src);
diff --git a/tokio/tests/fs_open_options.rs b/tokio/tests/fs_open_options.rs
new file mode 100644
index 00000000000..e8d8b51b39f
--- /dev/null
+++ b/tokio/tests/fs_open_options.rs
@@ -0,0 +1,80 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // WASI does not support all fs operations
+
+use std::io::Write;
+use tempfile::NamedTempFile;
+use tokio::fs::OpenOptions;
+use tokio::io::AsyncReadExt;
+
+const HELLO: &[u8] = b"hello world...";
+
+#[tokio::test]
+async fn open_with_open_options_and_read() {
+    let mut tempfile = NamedTempFile::new().unwrap();
+    tempfile.write_all(HELLO).unwrap();
+
+    let mut file = OpenOptions::new().read(true).open(tempfile).await.unwrap();
+
+    let mut buf = [0; 1024];
+    let n = file.read(&mut buf).await.unwrap();
+
+    assert_eq!(n, HELLO.len());
+    assert_eq!(&buf[..n], HELLO);
+}
+
+#[tokio::test]
+async fn open_options_write() {
+    // TESTING HACK: use Debug output to check the stored data
+    assert!(format!("{:?}", OpenOptions::new().write(true)).contains("write: true"));
+}
+
+#[tokio::test]
+async fn open_options_append() {
+    // TESTING HACK: use Debug output to check the stored data
+    assert!(format!("{:?}", OpenOptions::new().append(true)).contains("append: true"));
+}
+
+#[tokio::test]
+async fn open_options_truncate() {
+    // TESTING HACK: use Debug output to check the stored data
+    assert!(format!("{:?}", OpenOptions::new().truncate(true)).contains("truncate: true"));
+}
+
+#[tokio::test]
+async fn open_options_create() {
+    // TESTING HACK: use Debug output to check the stored data
+    assert!(format!("{:?}", OpenOptions::new().create(true)).contains("create: true"));
+}
+
+#[tokio::test]
+async fn open_options_create_new() {
+    // TESTING HACK: use Debug output to check the stored data
+    assert!(format!("{:?}", OpenOptions::new().create_new(true)).contains("create_new: true"));
+}
+
+#[tokio::test]
+#[cfg(unix)]
+async fn open_options_mode() {
+    // TESTING HACK: use Debug output to check the stored data
+    assert!(format!("{:?}", OpenOptions::new().mode(0o644)).contains("mode: 420 "));
+}
+
+#[tokio::test]
+#[cfg(target_os = "linux")]
+async fn open_options_custom_flags_linux() {
+    // TESTING HACK: use Debug output to check the stored data
+    assert!(
+        format!("{:?}", OpenOptions::new().custom_flags(libc::O_TRUNC))
+            .contains("custom_flags: 512,")
+    );
+}
+
+#[tokio::test]
+#[cfg(any(target_os = "freebsd", target_os = "macos"))]
+async fn open_options_custom_flags_bsd_family() {
+    // TESTING HACK: use Debug output to check the stored data
+    assert!(
+        format!("{:?}", OpenOptions::new().custom_flags(libc::O_NOFOLLOW))
+            .contains("custom_flags: 256,")
+    );
+}
diff --git a/tokio/tests/fs_open_options_windows.rs b/tokio/tests/fs_open_options_windows.rs
new file mode 100644
index 00000000000..398e6a12b36
--- /dev/null
+++ b/tokio/tests/fs_open_options_windows.rs
@@ -0,0 +1,51 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // WASI does not support all fs operations
+#![cfg(windows)]
+
+use tokio::fs::OpenOptions;
+use windows_sys::Win32::Storage::FileSystem;
+
+#[tokio::test]
+#[cfg(windows)]
+async fn open_options_windows_access_mode() {
+    // TESTING HACK: use Debug output to check the stored data
+    assert!(format!("{:?}", OpenOptions::new().access_mode(0)).contains("access_mode: Some(0)"));
+}
+
+#[tokio::test]
+#[cfg(windows)]
+async fn open_options_windows_share_mode() {
+    // TESTING HACK: use Debug output to check the stored data
+    assert!(format!("{:?}", OpenOptions::new().share_mode(0)).contains("share_mode: 0,"));
+}
+
+#[tokio::test]
+#[cfg(windows)]
+async fn open_options_windows_custom_flags() {
+    // TESTING HACK: use Debug output to check the stored data
+    assert!(format!(
+        "{:?}",
+        OpenOptions::new().custom_flags(FileSystem::FILE_FLAG_DELETE_ON_CLOSE)
+    )
+    .contains("custom_flags: 67108864,"));
+}
+
+#[tokio::test]
+#[cfg(windows)]
+async fn open_options_windows_attributes() {
+    assert!(format!(
+        "{:?}",
+        OpenOptions::new().attributes(FileSystem::FILE_ATTRIBUTE_HIDDEN)
+    )
+    .contains("attributes: 2,"));
+}
+
+#[tokio::test]
+#[cfg(windows)]
+async fn open_options_windows_security_qos_flags() {
+    assert!(format!(
+        "{:?}",
+        OpenOptions::new().security_qos_flags(FileSystem::SECURITY_IDENTIFICATION)
+    )
+    .contains("security_qos_flags: 1114112,"));
+}
diff --git a/tokio/tests/fs_remove_dir_all.rs b/tokio/tests/fs_remove_dir_all.rs
new file mode 100644
index 00000000000..53a2fd34f36
--- /dev/null
+++ b/tokio/tests/fs_remove_dir_all.rs
@@ -0,0 +1,31 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // WASI does not support all fs operations
+
+use tempfile::tempdir;
+use tokio::fs;
+
+#[tokio::test]
+async fn remove_dir_all() {
+    let temp_dir = tempdir().unwrap();
+
+    let test_dir = temp_dir.path().join("test");
+    fs::create_dir(&test_dir).await.unwrap();
+
+    let file_path = test_dir.as_path().join("a.txt");
+
+    fs::write(&file_path, b"Hello File!").await.unwrap();
+
+    fs::remove_dir_all(test_dir.as_path()).await.unwrap();
+
+    // test dir should no longer exist
+    match fs::try_exists(test_dir).await {
+        Ok(exists) => assert!(!exists),
+        Err(_) => println!("ignored try_exists error after remove_dir_all"),
+    };
+
+    // contents should no longer exist
+    match fs::try_exists(file_path).await {
+        Ok(exists) => assert!(!exists),
+        Err(_) => println!("ignored try_exists error after remove_dir_all"),
+    };
+}
diff --git a/tokio/tests/fs_remove_file.rs b/tokio/tests/fs_remove_file.rs
new file mode 100644
index 00000000000..14fd680dabe
--- /dev/null
+++ b/tokio/tests/fs_remove_file.rs
@@ -0,0 +1,24 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // WASI does not support all fs operations
+
+use tempfile::tempdir;
+use tokio::fs;
+
+#[tokio::test]
+async fn remove_file() {
+    let temp_dir = tempdir().unwrap();
+
+    let file_path = temp_dir.path().join("a.txt");
+
+    fs::write(&file_path, b"Hello File!").await.unwrap();
+
+    assert!(fs::try_exists(&file_path).await.unwrap());
+
+    fs::remove_file(&file_path).await.unwrap();
+
+    // should no longer exist
+    match fs::try_exists(file_path).await {
+        Ok(exists) => assert!(!exists),
+        Err(_) => println!("ignored try_exists error after remove_file"),
+    };
+}
diff --git a/tokio/tests/fs_rename.rs b/tokio/tests/fs_rename.rs
new file mode 100644
index 00000000000..382fea079bd
--- /dev/null
+++ b/tokio/tests/fs_rename.rs
@@ -0,0 +1,28 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // WASI does not support all fs operations
+
+use tempfile::tempdir;
+use tokio::fs;
+
+#[tokio::test]
+async fn rename_file() {
+    let temp_dir = tempdir().unwrap();
+
+    let file_path = temp_dir.path().join("a.txt");
+
+    fs::write(&file_path, b"Hello File!").await.unwrap();
+
+    assert!(fs::try_exists(&file_path).await.unwrap());
+
+    let new_file_path = temp_dir.path().join("b.txt");
+
+    fs::rename(&file_path, &new_file_path).await.unwrap();
+
+    assert!(fs::try_exists(new_file_path).await.unwrap());
+
+    // original file should no longer exist
+    match fs::try_exists(file_path).await {
+        Ok(exists) => assert!(!exists),
+        Err(_) => println!("ignored try_exists error after rename"),
+    };
+}
diff --git a/tokio/tests/fs_symlink_dir_windows.rs b/tokio/tests/fs_symlink_dir_windows.rs
new file mode 100644
index 00000000000..d80354268a2
--- /dev/null
+++ b/tokio/tests/fs_symlink_dir_windows.rs
@@ -0,0 +1,31 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // WASI does not support all fs operations
+#![cfg(windows)]
+
+use tempfile::tempdir;
+use tokio::fs;
+
+#[tokio::test]
+async fn symlink_file_windows() {
+    const FILE_NAME: &str = "abc.txt";
+
+    let temp_dir = tempdir().unwrap();
+
+    let dir1 = temp_dir.path().join("a");
+    fs::create_dir(&dir1).await.unwrap();
+
+    let file1 = dir1.as_path().join(FILE_NAME);
+    fs::write(&file1, b"Hello File!").await.unwrap();
+
+    let dir2 = temp_dir.path().join("b");
+    fs::symlink_dir(&dir1, &dir2).await.unwrap();
+
+    fs::write(&file1, b"new data!").await.unwrap();
+
+    let file2 = dir2.as_path().join(FILE_NAME);
+
+    let from = fs::read(&file1).await.unwrap();
+    let to = fs::read(&file2).await.unwrap();
+
+    assert_eq!(from, to);
+}
diff --git a/tokio/tests/fs_symlink_file_windows.rs b/tokio/tests/fs_symlink_file_windows.rs
new file mode 100644
index 00000000000..50eaf8aab75
--- /dev/null
+++ b/tokio/tests/fs_symlink_file_windows.rs
@@ -0,0 +1,24 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // WASI does not support all fs operations
+#![cfg(windows)]
+
+use tempfile::tempdir;
+use tokio::fs;
+
+#[tokio::test]
+async fn symlink_file_windows() {
+    let dir = tempdir().unwrap();
+
+    let source_path = dir.path().join("foo.txt");
+    let dest_path = dir.path().join("bar.txt");
+
+    fs::write(&source_path, b"Hello File!").await.unwrap();
+    fs::symlink_file(&source_path, &dest_path).await.unwrap();
+
+    fs::write(&source_path, b"new data!").await.unwrap();
+
+    let from = fs::read(&source_path).await.unwrap();
+    let to = fs::read(&dest_path).await.unwrap();
+
+    assert_eq!(from, to);
+}
diff --git a/tokio/tests/fs_try_exists.rs b/tokio/tests/fs_try_exists.rs
new file mode 100644
index 00000000000..00d23650015
--- /dev/null
+++ b/tokio/tests/fs_try_exists.rs
@@ -0,0 +1,44 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // WASI does not support all fs operations
+
+use tempfile::tempdir;
+use tokio::fs;
+
+#[tokio::test]
+async fn try_exists() {
+    let dir = tempdir().unwrap();
+
+    let existing_path = dir.path().join("foo.txt");
+    fs::write(&existing_path, b"Hello File!").await.unwrap();
+    let nonexisting_path = dir.path().join("bar.txt");
+
+    assert!(fs::try_exists(existing_path).await.unwrap());
+    assert!(!fs::try_exists(nonexisting_path).await.unwrap());
+    // FreeBSD root user always has permission to stat.
+    #[cfg(all(unix, not(target_os = "freebsd")))]
+    {
+        use std::os::unix::prelude::PermissionsExt;
+        let permission_denied_directory_path = dir.path().join("baz");
+        fs::create_dir(&permission_denied_directory_path)
+            .await
+            .unwrap();
+        let permission_denied_file_path = permission_denied_directory_path.join("baz.txt");
+        fs::write(&permission_denied_file_path, b"Hello File!")
+            .await
+            .unwrap();
+        let mut perms = tokio::fs::metadata(&permission_denied_directory_path)
+            .await
+            .unwrap()
+            .permissions();
+
+        perms.set_mode(0o244);
+        fs::set_permissions(&permission_denied_directory_path, perms)
+            .await
+            .unwrap();
+        let permission_denied_result = fs::try_exists(permission_denied_file_path).await;
+        assert_eq!(
+            permission_denied_result.err().unwrap().kind(),
+            std::io::ErrorKind::PermissionDenied
+        );
+    }
+}
diff --git a/tokio/tests/io_driver.rs b/tokio/tests/io_driver.rs
index 2ca56301de0..97018e0f967 100644
--- a/tokio/tests/io_driver.rs
+++ b/tokio/tests/io_driver.rs
@@ -80,7 +80,7 @@ fn test_drop_on_notify() {
     drop(task);
 
     // Establish a connection to the acceptor
-    let _s = TcpStream::connect(&addr).unwrap();
+    let _s = TcpStream::connect(addr).unwrap();
 
     // Force the reactor to turn
     rt.block_on(async {});
diff --git a/tokio/tests/macros_join.rs b/tokio/tests/macros_join.rs
index 16e7c43102f..7866ac086fa 100644
--- a/tokio/tests/macros_join.rs
+++ b/tokio/tests/macros_join.rs
@@ -1,5 +1,5 @@
 #![cfg(feature = "macros")]
-#![allow(clippy::blacklisted_name)]
+#![allow(clippy::disallowed_names)]
 use std::sync::Arc;
 
 #[cfg(tokio_wasm_not_wasi)]
@@ -153,3 +153,9 @@ async fn a_different_future_is_polled_first_every_time_poll_fn_is_polled() {
         *poll_order.lock().unwrap()
     );
 }
+
+#[tokio::test]
+#[allow(clippy::unit_cmp)]
+async fn empty_join() {
+    assert_eq!(tokio::join!(), ());
+}
diff --git a/tokio/tests/macros_select.rs b/tokio/tests/macros_select.rs
index 60f3738c991..26d6fec874b 100644
--- a/tokio/tests/macros_select.rs
+++ b/tokio/tests/macros_select.rs
@@ -1,5 +1,5 @@
 #![cfg(feature = "macros")]
-#![allow(clippy::blacklisted_name)]
+#![allow(clippy::disallowed_names)]
 
 #[cfg(tokio_wasm_not_wasi)]
 use wasm_bindgen_test::wasm_bindgen_test as maybe_tokio_test;
diff --git a/tokio/tests/macros_try_join.rs b/tokio/tests/macros_try_join.rs
index 209516bb998..74b1c9f9481 100644
--- a/tokio/tests/macros_try_join.rs
+++ b/tokio/tests/macros_try_join.rs
@@ -1,5 +1,5 @@
 #![cfg(feature = "macros")]
-#![allow(clippy::blacklisted_name)]
+#![allow(clippy::disallowed_names)]
 
 use std::sync::Arc;
 
@@ -183,3 +183,8 @@ async fn a_different_future_is_polled_first_every_time_poll_fn_is_polled() {
         *poll_order.lock().unwrap()
     );
 }
+
+#[tokio::test]
+async fn empty_try_join() {
+    assert_eq!(tokio::try_join!() as Result<_, ()>, Ok(()));
+}
diff --git a/tokio/tests/net_named_pipe.rs b/tokio/tests/net_named_pipe.rs
index c42122465c0..02c8a0919f5 100644
--- a/tokio/tests/net_named_pipe.rs
+++ b/tokio/tests/net_named_pipe.rs
@@ -5,7 +5,7 @@ use std::io;
 use std::mem;
 use std::os::windows::io::AsRawHandle;
 use std::time::Duration;
-use tokio::io::AsyncWriteExt;
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
 use tokio::net::windows::named_pipe::{ClientOptions, PipeMode, ServerOptions};
 use tokio::time;
 use windows_sys::Win32::Foundation::{ERROR_NO_DATA, ERROR_PIPE_BUSY, NO_ERROR, UNICODE_STRING};
@@ -327,17 +327,51 @@ async fn test_named_pipe_multi_client_ready() -> io::Result<()> {
     Ok(())
 }
 
-// This tests what happens when a client tries to disconnect.
+// This tests that message mode works as expected.
 #[tokio::test]
 async fn test_named_pipe_mode_message() -> io::Result<()> {
-    const PIPE_NAME: &str = r"\\.\pipe\test-named-pipe-mode-message";
+    // it's easy to accidentally get a seemingly working test here because byte pipes
+    // often return contents at write boundaries. to make sure we're doing the right thing we
+    // explicitly test that it doesn't work in byte mode.
+    _named_pipe_mode_message(PipeMode::Message).await?;
+    _named_pipe_mode_message(PipeMode::Byte).await
+}
+
+async fn _named_pipe_mode_message(mode: PipeMode) -> io::Result<()> {
+    let pipe_name = format!(
+        r"\\.\pipe\test-named-pipe-mode-message-{}",
+        matches!(mode, PipeMode::Message)
+    );
+    let mut buf = [0u8; 32];
 
-    let server = ServerOptions::new()
-        .pipe_mode(PipeMode::Message)
-        .create(PIPE_NAME)?;
+    let mut server = ServerOptions::new()
+        .first_pipe_instance(true)
+        .pipe_mode(mode)
+        .create(&pipe_name)?;
+
+    let mut client = ClientOptions::new().pipe_mode(mode).open(&pipe_name)?;
 
-    let _ = ClientOptions::new().open(PIPE_NAME)?;
     server.connect().await?;
+
+    // this needs a few iterations, presumably Windows waits for a few calls before merging buffers
+    for _ in 0..10 {
+        client.write_all(b"hello").await?;
+        server.write_all(b"world").await?;
+    }
+    for _ in 0..10 {
+        let n = server.read(&mut buf).await?;
+        if buf[..n] != b"hello"[..] {
+            assert!(matches!(mode, PipeMode::Byte));
+            return Ok(());
+        }
+        let n = client.read(&mut buf).await?;
+        if buf[..n] != b"world"[..] {
+            assert!(matches!(mode, PipeMode::Byte));
+            return Ok(());
+        }
+    }
+    // byte mode should have errored before.
+    assert!(matches!(mode, PipeMode::Message));
     Ok(())
 }
 
@@ -383,7 +417,7 @@ fn num_instances(pipe_name: impl AsRef<str>) -> io::Result<u32> {
 
     let status = unsafe {
         ntioapi::NtQueryDirectoryFile(
-            root.as_raw_handle(),
+            root.as_raw_handle().cast(),
             std::ptr::null_mut(),
             None,
             std::ptr::null_mut(),
diff --git a/tokio/tests/net_unix_pipe.rs b/tokio/tests/net_unix_pipe.rs
new file mode 100644
index 00000000000..c96d6e70fbd
--- /dev/null
+++ b/tokio/tests/net_unix_pipe.rs
@@ -0,0 +1,429 @@
+#![cfg(feature = "full")]
+#![cfg(unix)]
+
+use tokio::io::{AsyncReadExt, AsyncWriteExt, Interest};
+use tokio::net::unix::pipe;
+use tokio_test::task;
+use tokio_test::{assert_err, assert_ok, assert_pending, assert_ready_ok};
+
+use std::fs::File;
+use std::io;
+use std::os::unix::fs::OpenOptionsExt;
+use std::os::unix::io::AsRawFd;
+use std::path::{Path, PathBuf};
+
+/// Helper struct which will clean up temporary files once dropped.
+struct TempFifo {
+    path: PathBuf,
+    _dir: tempfile::TempDir,
+}
+
+impl TempFifo {
+    fn new(name: &str) -> io::Result<TempFifo> {
+        let dir = tempfile::Builder::new()
+            .prefix("tokio-fifo-tests")
+            .tempdir()?;
+        let path = dir.path().join(name);
+        nix::unistd::mkfifo(&path, nix::sys::stat::Mode::S_IRWXU)?;
+
+        Ok(TempFifo { path, _dir: dir })
+    }
+}
+
+impl AsRef<Path> for TempFifo {
+    fn as_ref(&self) -> &Path {
+        self.path.as_ref()
+    }
+}
+
+#[tokio::test]
+async fn fifo_simple_send() -> io::Result<()> {
+    const DATA: &[u8] = b"this is some data to write to the fifo";
+
+    let fifo = TempFifo::new("simple_send")?;
+
+    // Create a reading task which should wait for data from the pipe.
+    let mut reader = pipe::OpenOptions::new().open_receiver(&fifo)?;
+    let mut read_fut = task::spawn(async move {
+        let mut buf = vec![0; DATA.len()];
+        reader.read_exact(&mut buf).await?;
+        Ok::<_, io::Error>(buf)
+    });
+    assert_pending!(read_fut.poll());
+
+    let mut writer = pipe::OpenOptions::new().open_sender(&fifo)?;
+    writer.write_all(DATA).await?;
+
+    // Let the IO driver poll events for the reader.
+    while !read_fut.is_woken() {
+        tokio::task::yield_now().await;
+    }
+
+    // Reading task should be ready now.
+    let read_data = assert_ready_ok!(read_fut.poll());
+    assert_eq!(&read_data, DATA);
+
+    Ok(())
+}
+
+#[tokio::test]
+#[cfg(target_os = "linux")]
+async fn fifo_simple_send_sender_first() -> io::Result<()> {
+    const DATA: &[u8] = b"this is some data to write to the fifo";
+
+    // Create a new fifo file with *no reading ends open*.
+    let fifo = TempFifo::new("simple_send_sender_first")?;
+
+    // Simple `open_sender` should fail with ENXIO (no such device or address).
+    let err = assert_err!(pipe::OpenOptions::new().open_sender(&fifo));
+    assert_eq!(err.raw_os_error(), Some(libc::ENXIO));
+
+    // `open_sender` in read-write mode should succeed and the pipe should be ready to write.
+    let mut writer = pipe::OpenOptions::new()
+        .read_write(true)
+        .open_sender(&fifo)?;
+    writer.write_all(DATA).await?;
+
+    // Read the written data and validate.
+    let mut reader = pipe::OpenOptions::new().open_receiver(&fifo)?;
+    let mut read_data = vec![0; DATA.len()];
+    reader.read_exact(&mut read_data).await?;
+    assert_eq!(&read_data, DATA);
+
+    Ok(())
+}
+
+// Opens a FIFO file, write and *close the writer*.
+async fn write_and_close(path: impl AsRef<Path>, msg: &[u8]) -> io::Result<()> {
+    let mut writer = pipe::OpenOptions::new().open_sender(path)?;
+    writer.write_all(msg).await?;
+    drop(writer); // Explicit drop.
+    Ok(())
+}
+
+/// Checks EOF behavior with single reader and writers sequentially opening
+/// and closing a FIFO.
+#[tokio::test]
+async fn fifo_multiple_writes() -> io::Result<()> {
+    const DATA: &[u8] = b"this is some data to write to the fifo";
+
+    let fifo = TempFifo::new("fifo_multiple_writes")?;
+
+    let mut reader = pipe::OpenOptions::new().open_receiver(&fifo)?;
+
+    write_and_close(&fifo, DATA).await?;
+    let ev = reader.ready(Interest::READABLE).await?;
+    assert!(ev.is_readable());
+    let mut read_data = vec![0; DATA.len()];
+    assert_ok!(reader.read_exact(&mut read_data).await);
+
+    // Check that reader hits EOF.
+    let err = assert_err!(reader.read_exact(&mut read_data).await);
+    assert_eq!(err.kind(), io::ErrorKind::UnexpectedEof);
+
+    // Write more data and read again.
+    write_and_close(&fifo, DATA).await?;
+    assert_ok!(reader.read_exact(&mut read_data).await);
+
+    Ok(())
+}
+
+/// Checks behavior of a resilient reader (Receiver in O_RDWR access mode)
+/// with writers sequentially opening and closing a FIFO.
+#[tokio::test]
+#[cfg(target_os = "linux")]
+async fn fifo_resilient_reader() -> io::Result<()> {
+    const DATA: &[u8] = b"this is some data to write to the fifo";
+
+    let fifo = TempFifo::new("fifo_resilient_reader")?;
+
+    // Open reader in read-write access mode.
+    let mut reader = pipe::OpenOptions::new()
+        .read_write(true)
+        .open_receiver(&fifo)?;
+
+    write_and_close(&fifo, DATA).await?;
+    let ev = reader.ready(Interest::READABLE).await?;
+    let mut read_data = vec![0; DATA.len()];
+    reader.read_exact(&mut read_data).await?;
+
+    // Check that reader didn't hit EOF.
+    assert!(!ev.is_read_closed());
+
+    // Resilient reader can asynchronously wait for the next writer.
+    let mut second_read_fut = task::spawn(reader.read_exact(&mut read_data));
+    assert_pending!(second_read_fut.poll());
+
+    // Write more data and read again.
+    write_and_close(&fifo, DATA).await?;
+    assert_ok!(second_read_fut.await);
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn open_detects_not_a_fifo() -> io::Result<()> {
+    let dir = tempfile::Builder::new()
+        .prefix("tokio-fifo-tests")
+        .tempdir()
+        .unwrap();
+    let path = dir.path().join("not_a_fifo");
+
+    // Create an ordinary file.
+    File::create(&path)?;
+
+    // Check if Sender detects invalid file type.
+    let err = assert_err!(pipe::OpenOptions::new().open_sender(&path));
+    assert_eq!(err.kind(), io::ErrorKind::InvalidInput);
+
+    // Check if Receiver detects invalid file type.
+    let err = assert_err!(pipe::OpenOptions::new().open_sender(&path));
+    assert_eq!(err.kind(), io::ErrorKind::InvalidInput);
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn from_file() -> io::Result<()> {
+    const DATA: &[u8] = b"this is some data to write to the fifo";
+
+    let fifo = TempFifo::new("from_file")?;
+
+    // Construct a Receiver from a File.
+    let file = std::fs::OpenOptions::new()
+        .read(true)
+        .custom_flags(libc::O_NONBLOCK)
+        .open(&fifo)?;
+    let mut reader = pipe::Receiver::from_file(file)?;
+
+    // Construct a Sender from a File.
+    let file = std::fs::OpenOptions::new()
+        .write(true)
+        .custom_flags(libc::O_NONBLOCK)
+        .open(&fifo)?;
+    let mut writer = pipe::Sender::from_file(file)?;
+
+    // Write and read some data to test async.
+    let mut read_fut = task::spawn(async move {
+        let mut buf = vec![0; DATA.len()];
+        reader.read_exact(&mut buf).await?;
+        Ok::<_, io::Error>(buf)
+    });
+    assert_pending!(read_fut.poll());
+
+    writer.write_all(DATA).await?;
+
+    let read_data = assert_ok!(read_fut.await);
+    assert_eq!(&read_data, DATA);
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn from_file_detects_not_a_fifo() -> io::Result<()> {
+    let dir = tempfile::Builder::new()
+        .prefix("tokio-fifo-tests")
+        .tempdir()
+        .unwrap();
+    let path = dir.path().join("not_a_fifo");
+
+    // Create an ordinary file.
+    File::create(&path)?;
+
+    // Check if Sender detects invalid file type.
+    let file = std::fs::OpenOptions::new().write(true).open(&path)?;
+    let err = assert_err!(pipe::Sender::from_file(file));
+    assert_eq!(err.kind(), io::ErrorKind::InvalidInput);
+
+    // Check if Receiver detects invalid file type.
+    let file = std::fs::OpenOptions::new().read(true).open(&path)?;
+    let err = assert_err!(pipe::Receiver::from_file(file));
+    assert_eq!(err.kind(), io::ErrorKind::InvalidInput);
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn from_file_detects_wrong_access_mode() -> io::Result<()> {
+    let fifo = TempFifo::new("wrong_access_mode")?;
+
+    // Open a read end to open the fifo for writing.
+    let _reader = pipe::OpenOptions::new().open_receiver(&fifo)?;
+
+    // Check if Receiver detects write-only access mode.
+    let wronly = std::fs::OpenOptions::new()
+        .write(true)
+        .custom_flags(libc::O_NONBLOCK)
+        .open(&fifo)?;
+    let err = assert_err!(pipe::Receiver::from_file(wronly));
+    assert_eq!(err.kind(), io::ErrorKind::InvalidInput);
+
+    // Check if Sender detects read-only access mode.
+    let rdonly = std::fs::OpenOptions::new()
+        .read(true)
+        .custom_flags(libc::O_NONBLOCK)
+        .open(&fifo)?;
+    let err = assert_err!(pipe::Sender::from_file(rdonly));
+    assert_eq!(err.kind(), io::ErrorKind::InvalidInput);
+
+    Ok(())
+}
+
+fn is_nonblocking<T: AsRawFd>(fd: &T) -> io::Result<bool> {
+    let flags = nix::fcntl::fcntl(fd.as_raw_fd(), nix::fcntl::F_GETFL)?;
+    Ok((flags & libc::O_NONBLOCK) != 0)
+}
+
+#[tokio::test]
+async fn from_file_sets_nonblock() -> io::Result<()> {
+    let fifo = TempFifo::new("sets_nonblock")?;
+
+    // Open read and write ends to let blocking files open.
+    let _reader = pipe::OpenOptions::new().open_receiver(&fifo)?;
+    let _writer = pipe::OpenOptions::new().open_sender(&fifo)?;
+
+    // Check if Receiver sets the pipe in non-blocking mode.
+    let rdonly = std::fs::OpenOptions::new().read(true).open(&fifo)?;
+    assert!(!is_nonblocking(&rdonly)?);
+    let reader = pipe::Receiver::from_file(rdonly)?;
+    assert!(is_nonblocking(&reader)?);
+
+    // Check if Sender sets the pipe in non-blocking mode.
+    let wronly = std::fs::OpenOptions::new().write(true).open(&fifo)?;
+    assert!(!is_nonblocking(&wronly)?);
+    let writer = pipe::Sender::from_file(wronly)?;
+    assert!(is_nonblocking(&writer)?);
+
+    Ok(())
+}
+
+fn writable_by_poll(writer: &pipe::Sender) -> bool {
+    task::spawn(writer.writable()).poll().is_ready()
+}
+
+#[tokio::test]
+async fn try_read_write() -> io::Result<()> {
+    const DATA: &[u8] = b"this is some data to write to the fifo";
+
+    // Create a pipe pair over a fifo file.
+    let fifo = TempFifo::new("try_read_write")?;
+    let reader = pipe::OpenOptions::new().open_receiver(&fifo)?;
+    let writer = pipe::OpenOptions::new().open_sender(&fifo)?;
+
+    // Fill the pipe buffer with `try_write`.
+    let mut write_data = Vec::new();
+    while writable_by_poll(&writer) {
+        match writer.try_write(DATA) {
+            Ok(n) => write_data.extend(&DATA[..n]),
+            Err(e) => {
+                assert_eq!(e.kind(), io::ErrorKind::WouldBlock);
+                break;
+            }
+        }
+    }
+
+    // Drain the pipe buffer with `try_read`.
+    let mut read_data = vec![0; write_data.len()];
+    let mut i = 0;
+    while i < write_data.len() {
+        reader.readable().await?;
+        match reader.try_read(&mut read_data[i..]) {
+            Ok(n) => i += n,
+            Err(e) => {
+                assert_eq!(e.kind(), io::ErrorKind::WouldBlock);
+                continue;
+            }
+        }
+    }
+
+    assert_eq!(read_data, write_data);
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn try_read_write_vectored() -> io::Result<()> {
+    const DATA: &[u8] = b"this is some data to write to the fifo";
+
+    // Create a pipe pair over a fifo file.
+    let fifo = TempFifo::new("try_read_write_vectored")?;
+    let reader = pipe::OpenOptions::new().open_receiver(&fifo)?;
+    let writer = pipe::OpenOptions::new().open_sender(&fifo)?;
+
+    let write_bufs: Vec<_> = DATA.chunks(3).map(io::IoSlice::new).collect();
+
+    // Fill the pipe buffer with `try_write_vectored`.
+    let mut write_data = Vec::new();
+    while writable_by_poll(&writer) {
+        match writer.try_write_vectored(&write_bufs) {
+            Ok(n) => write_data.extend(&DATA[..n]),
+            Err(e) => {
+                assert_eq!(e.kind(), io::ErrorKind::WouldBlock);
+                break;
+            }
+        }
+    }
+
+    // Drain the pipe buffer with `try_read_vectored`.
+    let mut read_data = vec![0; write_data.len()];
+    let mut i = 0;
+    while i < write_data.len() {
+        reader.readable().await?;
+
+        let mut read_bufs: Vec<_> = read_data[i..]
+            .chunks_mut(0x10000)
+            .map(io::IoSliceMut::new)
+            .collect();
+        match reader.try_read_vectored(&mut read_bufs) {
+            Ok(n) => i += n,
+            Err(e) => {
+                assert_eq!(e.kind(), io::ErrorKind::WouldBlock);
+                continue;
+            }
+        }
+    }
+
+    assert_eq!(read_data, write_data);
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn try_read_buf() -> std::io::Result<()> {
+    const DATA: &[u8] = b"this is some data to write to the fifo";
+
+    // Create a pipe pair over a fifo file.
+    let fifo = TempFifo::new("try_read_write_vectored")?;
+    let reader = pipe::OpenOptions::new().open_receiver(&fifo)?;
+    let writer = pipe::OpenOptions::new().open_sender(&fifo)?;
+
+    // Fill the pipe buffer with `try_write`.
+    let mut write_data = Vec::new();
+    while writable_by_poll(&writer) {
+        match writer.try_write(DATA) {
+            Ok(n) => write_data.extend(&DATA[..n]),
+            Err(e) => {
+                assert_eq!(e.kind(), io::ErrorKind::WouldBlock);
+                break;
+            }
+        }
+    }
+
+    // Drain the pipe buffer with `try_read_buf`.
+    let mut read_data = vec![0; write_data.len()];
+    let mut i = 0;
+    while i < write_data.len() {
+        reader.readable().await?;
+        match reader.try_read_buf(&mut read_data) {
+            Ok(n) => i += n,
+            Err(e) => {
+                assert_eq!(e.kind(), io::ErrorKind::WouldBlock);
+                continue;
+            }
+        }
+    }
+
+    assert_eq!(read_data, write_data);
+
+    Ok(())
+}
diff --git a/tokio/tests/rt_common.rs b/tokio/tests/rt_common.rs
index ef0c2a222dc..22d821fa1ad 100644
--- a/tokio/tests/rt_common.rs
+++ b/tokio/tests/rt_common.rs
@@ -661,7 +661,7 @@ rt_test! {
                 loop {
                     // Don't use Tokio's `yield_now()` to avoid special defer
                     // logic.
-                    let _: () = futures::future::poll_fn(|cx| {
+                    futures::future::poll_fn::<(), _>(|cx| {
                         cx.waker().wake_by_ref();
                         std::task::Poll::Pending
                     }).await;
diff --git a/tokio/tests/rt_metrics.rs b/tokio/tests/rt_metrics.rs
index 2a9f998f082..fdb2fb5f551 100644
--- a/tokio/tests/rt_metrics.rs
+++ b/tokio/tests/rt_metrics.rs
@@ -31,6 +31,19 @@ fn num_idle_blocking_threads() {
     rt.block_on(async {
         time::sleep(Duration::from_millis(5)).await;
     });
+
+    // We need to wait until the blocking thread has become idle. Usually 5ms is
+    // enough for this to happen, but not always. When it isn't enough, sleep
+    // for another second. We don't always wait for a whole second since we want
+    // the test suite to finish quickly.
+    //
+    // Note that the timeout for idle threads to be killed is 10 seconds.
+    if 0 == rt.metrics().num_idle_blocking_threads() {
+        rt.block_on(async {
+            time::sleep(Duration::from_secs(1)).await;
+        });
+    }
+
     assert_eq!(1, rt.metrics().num_idle_blocking_threads());
 }
 
@@ -128,7 +141,7 @@ fn worker_noop_count() {
         time::sleep(Duration::from_millis(1)).await;
     });
     drop(rt);
-    assert!(2 <= metrics.worker_noop_count(0));
+    assert!(0 < metrics.worker_noop_count(0));
 
     let rt = threaded();
     let metrics = rt.metrics();
@@ -136,8 +149,8 @@ fn worker_noop_count() {
         time::sleep(Duration::from_millis(1)).await;
     });
     drop(rt);
-    assert!(1 <= metrics.worker_noop_count(0));
-    assert!(1 <= metrics.worker_noop_count(1));
+    assert!(0 < metrics.worker_noop_count(0));
+    assert!(0 < metrics.worker_noop_count(1));
 }
 
 #[test]
diff --git a/tokio/tests/support/leaked_buffers.rs b/tokio/tests/support/leaked_buffers.rs
index 3ee8a18967b..a6079fb707a 100644
--- a/tokio/tests/support/leaked_buffers.rs
+++ b/tokio/tests/support/leaked_buffers.rs
@@ -18,9 +18,9 @@ impl LeakedBuffers {
         }
     }
     pub unsafe fn create<'a>(&mut self, size: usize) -> &'a mut [u8] {
-        let mut new_mem = vec![0u8; size].into_boxed_slice();
-        let slice = std::slice::from_raw_parts_mut(new_mem.as_mut_ptr(), new_mem.len());
+        let new_mem = vec![0u8; size].into_boxed_slice();
         self.leaked_vecs.push(new_mem);
-        slice
+        let new_mem = self.leaked_vecs.last_mut().unwrap();
+        std::slice::from_raw_parts_mut(new_mem.as_mut_ptr(), new_mem.len())
     }
 }
diff --git a/tokio/tests/support/panic.rs b/tokio/tests/support/panic.rs
index 7f60c76f00a..df2f59d30ff 100644
--- a/tokio/tests/support/panic.rs
+++ b/tokio/tests/support/panic.rs
@@ -1,9 +1,8 @@
-use parking_lot::{const_mutex, Mutex};
 use std::panic;
-use std::sync::Arc;
+use std::sync::{Arc, Mutex};
 
 pub fn test_panic<Func: FnOnce() + panic::UnwindSafe>(func: Func) -> Option<String> {
-    static PANIC_MUTEX: Mutex<()> = const_mutex(());
+    static PANIC_MUTEX: Mutex<()> = Mutex::new(());
 
     {
         let _guard = PANIC_MUTEX.lock();
@@ -16,6 +15,7 @@ pub fn test_panic<Func: FnOnce() + panic::UnwindSafe>(func: Func) -> Option<Stri
                 let panic_location = panic_info.location().unwrap();
                 panic_file
                     .lock()
+                    .unwrap()
                     .clone_from(&Some(panic_location.file().to_string()));
             }));
         }
@@ -26,7 +26,7 @@ pub fn test_panic<Func: FnOnce() + panic::UnwindSafe>(func: Func) -> Option<Stri
         panic::set_hook(prev_hook);
 
         if result.is_err() {
-            panic_file.lock().clone()
+            panic_file.lock().unwrap().clone()
         } else {
             None
         }
diff --git a/tokio/tests/sync_broadcast.rs b/tokio/tests/sync_broadcast.rs
index 9aa34841e26..cd6692448bb 100644
--- a/tokio/tests/sync_broadcast.rs
+++ b/tokio/tests/sync_broadcast.rs
@@ -291,6 +291,7 @@ fn capacity_too_big() {
 }
 
 #[test]
+#[cfg(panic = "unwind")]
 #[cfg(not(tokio_wasm))] // wasm currently doesn't support unwinding
 fn panic_in_clone() {
     use std::panic::{self, AssertUnwindSafe};
@@ -526,3 +527,63 @@ fn resubscribe_to_closed_channel() {
     let mut rx_resub = rx.resubscribe();
     assert_closed!(rx_resub.try_recv());
 }
+
+#[test]
+fn sender_len() {
+    let (tx, mut rx1) = broadcast::channel(4);
+    let mut rx2 = tx.subscribe();
+
+    assert_eq!(tx.len(), 0);
+    assert!(tx.is_empty());
+
+    tx.send(1).unwrap();
+    tx.send(2).unwrap();
+    tx.send(3).unwrap();
+
+    assert_eq!(tx.len(), 3);
+    assert!(!tx.is_empty());
+
+    assert_recv!(rx1);
+    assert_recv!(rx1);
+
+    assert_eq!(tx.len(), 3);
+    assert!(!tx.is_empty());
+
+    assert_recv!(rx2);
+
+    assert_eq!(tx.len(), 2);
+    assert!(!tx.is_empty());
+
+    tx.send(4).unwrap();
+    tx.send(5).unwrap();
+    tx.send(6).unwrap();
+
+    assert_eq!(tx.len(), 4);
+    assert!(!tx.is_empty());
+}
+
+#[test]
+#[cfg(not(tokio_wasm_not_wasi))]
+fn sender_len_random() {
+    use rand::Rng;
+
+    let (tx, mut rx1) = broadcast::channel(16);
+    let mut rx2 = tx.subscribe();
+
+    for _ in 0..1000 {
+        match rand::thread_rng().gen_range(0..4) {
+            0 => {
+                let _ = rx1.try_recv();
+            }
+            1 => {
+                let _ = rx2.try_recv();
+            }
+            _ => {
+                tx.send(0).unwrap();
+            }
+        }
+
+        let expected_len = usize::min(usize::max(rx1.len(), rx2.len()), 16);
+        assert_eq!(tx.len(), expected_len);
+    }
+}
diff --git a/tokio/tests/sync_once_cell.rs b/tokio/tests/sync_once_cell.rs
index 18eaf9382bd..38dfa7ca0b6 100644
--- a/tokio/tests/sync_once_cell.rs
+++ b/tokio/tests/sync_once_cell.rs
@@ -4,178 +4,7 @@
 use std::mem;
 use std::ops::Drop;
 use std::sync::atomic::{AtomicU32, Ordering};
-use std::time::Duration;
-use tokio::runtime;
-use tokio::sync::{OnceCell, SetError};
-use tokio::time;
-
-async fn func1() -> u32 {
-    5
-}
-
-async fn func2() -> u32 {
-    time::sleep(Duration::from_millis(1)).await;
-    10
-}
-
-async fn func_err() -> Result<u32, ()> {
-    Err(())
-}
-
-async fn func_ok() -> Result<u32, ()> {
-    Ok(10)
-}
-
-async fn func_panic() -> u32 {
-    time::sleep(Duration::from_millis(1)).await;
-    panic!();
-}
-
-async fn sleep_and_set() -> u32 {
-    // Simulate sleep by pausing time and waiting for another thread to
-    // resume clock when calling `set`, then finding the cell being initialized
-    // by this call
-    time::sleep(Duration::from_millis(2)).await;
-    5
-}
-
-async fn advance_time_and_set(cell: &'static OnceCell<u32>, v: u32) -> Result<(), SetError<u32>> {
-    time::advance(Duration::from_millis(1)).await;
-    cell.set(v)
-}
-
-#[test]
-fn get_or_init() {
-    let rt = runtime::Builder::new_current_thread()
-        .enable_time()
-        .start_paused(true)
-        .build()
-        .unwrap();
-
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-
-    rt.block_on(async {
-        let handle1 = rt.spawn(async { ONCE.get_or_init(func1).await });
-        let handle2 = rt.spawn(async { ONCE.get_or_init(func2).await });
-
-        time::advance(Duration::from_millis(1)).await;
-        time::resume();
-
-        let result1 = handle1.await.unwrap();
-        let result2 = handle2.await.unwrap();
-
-        assert_eq!(*result1, 5);
-        assert_eq!(*result2, 5);
-    });
-}
-
-#[test]
-fn get_or_init_panic() {
-    let rt = runtime::Builder::new_current_thread()
-        .enable_time()
-        .build()
-        .unwrap();
-
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-
-    rt.block_on(async {
-        time::pause();
-
-        let handle1 = rt.spawn(async { ONCE.get_or_init(func1).await });
-        let handle2 = rt.spawn(async { ONCE.get_or_init(func_panic).await });
-
-        time::advance(Duration::from_millis(1)).await;
-
-        let result1 = handle1.await.unwrap();
-        let result2 = handle2.await.unwrap();
-
-        assert_eq!(*result1, 5);
-        assert_eq!(*result2, 5);
-    });
-}
-
-#[test]
-fn set_and_get() {
-    let rt = runtime::Builder::new_current_thread()
-        .enable_time()
-        .build()
-        .unwrap();
-
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-
-    rt.block_on(async {
-        let _ = rt.spawn(async { ONCE.set(5) }).await;
-        let value = ONCE.get().unwrap();
-        assert_eq!(*value, 5);
-    });
-}
-
-#[test]
-fn get_uninit() {
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-    let uninit = ONCE.get();
-    assert!(uninit.is_none());
-}
-
-#[test]
-fn set_twice() {
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-
-    let first = ONCE.set(5);
-    assert_eq!(first, Ok(()));
-    let second = ONCE.set(6);
-    assert!(second.err().unwrap().is_already_init_err());
-}
-
-#[test]
-fn set_while_initializing() {
-    let rt = runtime::Builder::new_current_thread()
-        .enable_time()
-        .build()
-        .unwrap();
-
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-
-    rt.block_on(async {
-        time::pause();
-
-        let handle1 = rt.spawn(async { ONCE.get_or_init(sleep_and_set).await });
-        let handle2 = rt.spawn(async { advance_time_and_set(&ONCE, 10).await });
-
-        time::advance(Duration::from_millis(2)).await;
-
-        let result1 = handle1.await.unwrap();
-        let result2 = handle2.await.unwrap();
-
-        assert_eq!(*result1, 5);
-        assert!(result2.err().unwrap().is_initializing_err());
-    });
-}
-
-#[test]
-fn get_or_try_init() {
-    let rt = runtime::Builder::new_current_thread()
-        .enable_time()
-        .start_paused(true)
-        .build()
-        .unwrap();
-
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-
-    rt.block_on(async {
-        let handle1 = rt.spawn(async { ONCE.get_or_try_init(func_err).await });
-        let handle2 = rt.spawn(async { ONCE.get_or_try_init(func_ok).await });
-
-        time::advance(Duration::from_millis(1)).await;
-        time::resume();
-
-        let result1 = handle1.await.unwrap();
-        assert!(result1.is_err());
-
-        let result2 = handle2.await.unwrap();
-        assert_eq!(*result2.unwrap(), 10);
-    });
-}
+use tokio::sync::OnceCell;
 
 #[test]
 fn drop_cell() {
@@ -272,3 +101,185 @@ fn from() {
     let cell = OnceCell::from(2);
     assert_eq!(*cell.get().unwrap(), 2);
 }
+
+#[cfg(feature = "parking_lot")]
+mod parking_lot {
+    use super::*;
+
+    use tokio::runtime;
+    use tokio::sync::SetError;
+    use tokio::time;
+
+    use std::time::Duration;
+
+    async fn func1() -> u32 {
+        5
+    }
+
+    async fn func2() -> u32 {
+        time::sleep(Duration::from_millis(1)).await;
+        10
+    }
+
+    async fn func_err() -> Result<u32, ()> {
+        Err(())
+    }
+
+    async fn func_ok() -> Result<u32, ()> {
+        Ok(10)
+    }
+
+    async fn func_panic() -> u32 {
+        time::sleep(Duration::from_millis(1)).await;
+        panic!();
+    }
+
+    async fn sleep_and_set() -> u32 {
+        // Simulate sleep by pausing time and waiting for another thread to
+        // resume clock when calling `set`, then finding the cell being initialized
+        // by this call
+        time::sleep(Duration::from_millis(2)).await;
+        5
+    }
+
+    async fn advance_time_and_set(
+        cell: &'static OnceCell<u32>,
+        v: u32,
+    ) -> Result<(), SetError<u32>> {
+        time::advance(Duration::from_millis(1)).await;
+        cell.set(v)
+    }
+
+    #[test]
+    fn get_or_init() {
+        let rt = runtime::Builder::new_current_thread()
+            .enable_time()
+            .start_paused(true)
+            .build()
+            .unwrap();
+
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+
+        rt.block_on(async {
+            let handle1 = rt.spawn(async { ONCE.get_or_init(func1).await });
+            let handle2 = rt.spawn(async { ONCE.get_or_init(func2).await });
+
+            time::advance(Duration::from_millis(1)).await;
+            time::resume();
+
+            let result1 = handle1.await.unwrap();
+            let result2 = handle2.await.unwrap();
+
+            assert_eq!(*result1, 5);
+            assert_eq!(*result2, 5);
+        });
+    }
+
+    #[test]
+    fn get_or_init_panic() {
+        let rt = runtime::Builder::new_current_thread()
+            .enable_time()
+            .build()
+            .unwrap();
+
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+
+        rt.block_on(async {
+            time::pause();
+
+            let handle1 = rt.spawn(async { ONCE.get_or_init(func1).await });
+            let handle2 = rt.spawn(async { ONCE.get_or_init(func_panic).await });
+
+            time::advance(Duration::from_millis(1)).await;
+
+            let result1 = handle1.await.unwrap();
+            let result2 = handle2.await.unwrap();
+
+            assert_eq!(*result1, 5);
+            assert_eq!(*result2, 5);
+        });
+    }
+
+    #[test]
+    fn set_and_get() {
+        let rt = runtime::Builder::new_current_thread()
+            .enable_time()
+            .build()
+            .unwrap();
+
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+
+        rt.block_on(async {
+            let _ = rt.spawn(async { ONCE.set(5) }).await;
+            let value = ONCE.get().unwrap();
+            assert_eq!(*value, 5);
+        });
+    }
+
+    #[test]
+    fn get_uninit() {
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+        let uninit = ONCE.get();
+        assert!(uninit.is_none());
+    }
+
+    #[test]
+    fn set_twice() {
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+
+        let first = ONCE.set(5);
+        assert_eq!(first, Ok(()));
+        let second = ONCE.set(6);
+        assert!(second.err().unwrap().is_already_init_err());
+    }
+
+    #[test]
+    fn set_while_initializing() {
+        let rt = runtime::Builder::new_current_thread()
+            .enable_time()
+            .build()
+            .unwrap();
+
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+
+        rt.block_on(async {
+            time::pause();
+
+            let handle1 = rt.spawn(async { ONCE.get_or_init(sleep_and_set).await });
+            let handle2 = rt.spawn(async { advance_time_and_set(&ONCE, 10).await });
+
+            time::advance(Duration::from_millis(2)).await;
+
+            let result1 = handle1.await.unwrap();
+            let result2 = handle2.await.unwrap();
+
+            assert_eq!(*result1, 5);
+            assert!(result2.err().unwrap().is_initializing_err());
+        });
+    }
+
+    #[test]
+    fn get_or_try_init() {
+        let rt = runtime::Builder::new_current_thread()
+            .enable_time()
+            .start_paused(true)
+            .build()
+            .unwrap();
+
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+
+        rt.block_on(async {
+            let handle1 = rt.spawn(async { ONCE.get_or_try_init(func_err).await });
+            let handle2 = rt.spawn(async { ONCE.get_or_try_init(func_ok).await });
+
+            time::advance(Duration::from_millis(1)).await;
+            time::resume();
+
+            let result1 = handle1.await.unwrap();
+            assert!(result1.is_err());
+
+            let result2 = handle2.await.unwrap();
+            assert_eq!(*result2.unwrap(), 10);
+        });
+    }
+}
diff --git a/tokio/tests/sync_watch.rs b/tokio/tests/sync_watch.rs
index 34f9b786710..d4f8ce87d95 100644
--- a/tokio/tests/sync_watch.rs
+++ b/tokio/tests/sync_watch.rs
@@ -213,6 +213,7 @@ fn reopened_after_subscribe() {
 }
 
 #[test]
+#[cfg(panic = "unwind")]
 #[cfg(not(tokio_wasm))] // wasm currently doesn't support unwinding
 fn send_modify_panic() {
     let (tx, mut rx) = watch::channel("one");
diff --git a/tokio/tests/task_blocking.rs b/tokio/tests/task_blocking.rs
index e5879332d0e..2999758ff36 100644
--- a/tokio/tests/task_blocking.rs
+++ b/tokio/tests/task_blocking.rs
@@ -1,7 +1,7 @@
 #![warn(rust_2018_idioms)]
 #![cfg(all(feature = "full", not(tokio_wasi)))] // Wasi doesn't support threads
 
-use tokio::{runtime, task};
+use tokio::{runtime, task, time};
 use tokio_test::assert_ok;
 
 use std::thread;
@@ -226,3 +226,84 @@ fn coop_disabled_in_block_in_place_in_block_on() {
 
     done_rx.recv().unwrap().unwrap();
 }
+
+#[cfg(feature = "test-util")]
+#[tokio::test(start_paused = true)]
+async fn blocking_when_paused() {
+    // Do not auto-advance time when we have started a blocking task that has
+    // not yet finished.
+    time::timeout(
+        Duration::from_secs(3),
+        task::spawn_blocking(|| thread::sleep(Duration::from_millis(1))),
+    )
+    .await
+    .expect("timeout should not trigger")
+    .expect("blocking task should finish");
+
+    // Really: Do not auto-advance time, even if the timeout is short and the
+    // blocking task runs for longer than that. It doesn't matter: Tokio time
+    // is paused; system time is not.
+    time::timeout(
+        Duration::from_millis(1),
+        task::spawn_blocking(|| thread::sleep(Duration::from_millis(50))),
+    )
+    .await
+    .expect("timeout should not trigger")
+    .expect("blocking task should finish");
+}
+
+#[cfg(feature = "test-util")]
+#[tokio::test(start_paused = true)]
+async fn blocking_task_wakes_paused_runtime() {
+    let t0 = std::time::Instant::now();
+    time::timeout(
+        Duration::from_secs(15),
+        task::spawn_blocking(|| thread::sleep(Duration::from_millis(1))),
+    )
+    .await
+    .expect("timeout should not trigger")
+    .expect("blocking task should finish");
+    assert!(
+        t0.elapsed() < Duration::from_secs(10),
+        "completing a spawn_blocking should wake the scheduler if it's parked while time is paused"
+    );
+}
+
+#[cfg(feature = "test-util")]
+#[tokio::test(start_paused = true)]
+async fn unawaited_blocking_task_wakes_paused_runtime() {
+    let t0 = std::time::Instant::now();
+
+    // When this task finishes, time should auto-advance, even though the
+    // JoinHandle has not been awaited yet.
+    let a = task::spawn_blocking(|| {
+        thread::sleep(Duration::from_millis(1));
+    });
+
+    crate::time::sleep(Duration::from_secs(15)).await;
+    a.await.expect("blocking task should finish");
+    assert!(
+        t0.elapsed() < Duration::from_secs(10),
+        "completing a spawn_blocking should wake the scheduler if it's parked while time is paused"
+    );
+}
+
+#[cfg(feature = "test-util")]
+#[tokio::test(start_paused = true)]
+async fn panicking_blocking_task_wakes_paused_runtime() {
+    let t0 = std::time::Instant::now();
+    let result = time::timeout(
+        Duration::from_secs(15),
+        task::spawn_blocking(|| {
+            thread::sleep(Duration::from_millis(1));
+            panic!("blocking task panicked");
+        }),
+    )
+    .await
+    .expect("timeout should not trigger");
+    assert!(result.is_err(), "blocking task should have panicked");
+    assert!(
+        t0.elapsed() < Duration::from_secs(10),
+        "completing a spawn_blocking should wake the scheduler if it's parked while time is paused"
+    );
+}
diff --git a/tokio/tests/task_join_set.rs b/tokio/tests/task_join_set.rs
index 20d4927212a..b1b6cf9665f 100644
--- a/tokio/tests/task_join_set.rs
+++ b/tokio/tests/task_join_set.rs
@@ -5,8 +5,6 @@ use tokio::sync::oneshot;
 use tokio::task::JoinSet;
 use tokio::time::Duration;
 
-use futures::future::FutureExt;
-
 fn rt() -> tokio::runtime::Runtime {
     tokio::runtime::Builder::new_current_thread()
         .build()
@@ -156,49 +154,6 @@ fn runtime_gone() {
         .is_cancelled());
 }
 
-// This ensures that `join_next` works correctly when the coop budget is
-// exhausted.
-#[tokio::test(flavor = "current_thread")]
-async fn join_set_coop() {
-    // Large enough to trigger coop.
-    const TASK_NUM: u32 = 1000;
-
-    static SEM: tokio::sync::Semaphore = tokio::sync::Semaphore::const_new(0);
-
-    let mut set = JoinSet::new();
-
-    for _ in 0..TASK_NUM {
-        set.spawn(async {
-            SEM.add_permits(1);
-        });
-    }
-
-    // Wait for all tasks to complete.
-    //
-    // Since this is a `current_thread` runtime, there's no race condition
-    // between the last permit being added and the task completing.
-    let _ = SEM.acquire_many(TASK_NUM).await.unwrap();
-
-    let mut count = 0;
-    let mut coop_count = 0;
-    loop {
-        match set.join_next().now_or_never() {
-            Some(Some(Ok(()))) => {}
-            Some(Some(Err(err))) => panic!("failed: {}", err),
-            None => {
-                coop_count += 1;
-                tokio::task::yield_now().await;
-                continue;
-            }
-            Some(None) => break,
-        }
-
-        count += 1;
-    }
-    assert!(coop_count >= 1);
-    assert_eq!(count, TASK_NUM);
-}
-
 #[tokio::test(start_paused = true)]
 async fn abort_all() {
     let mut set: JoinSet<()> = JoinSet::new();
@@ -228,3 +183,53 @@ async fn abort_all() {
     assert_eq!(count, 10);
     assert_eq!(set.len(), 0);
 }
+
+#[cfg(feature = "parking_lot")]
+mod parking_lot {
+    use super::*;
+
+    use futures::future::FutureExt;
+
+    // This ensures that `join_next` works correctly when the coop budget is
+    // exhausted.
+    #[tokio::test(flavor = "current_thread")]
+    async fn join_set_coop() {
+        // Large enough to trigger coop.
+        const TASK_NUM: u32 = 1000;
+
+        static SEM: tokio::sync::Semaphore = tokio::sync::Semaphore::const_new(0);
+
+        let mut set = JoinSet::new();
+
+        for _ in 0..TASK_NUM {
+            set.spawn(async {
+                SEM.add_permits(1);
+            });
+        }
+
+        // Wait for all tasks to complete.
+        //
+        // Since this is a `current_thread` runtime, there's no race condition
+        // between the last permit being added and the task completing.
+        let _ = SEM.acquire_many(TASK_NUM).await.unwrap();
+
+        let mut count = 0;
+        let mut coop_count = 0;
+        loop {
+            match set.join_next().now_or_never() {
+                Some(Some(Ok(()))) => {}
+                Some(Some(Err(err))) => panic!("failed: {}", err),
+                None => {
+                    coop_count += 1;
+                    tokio::task::yield_now().await;
+                    continue;
+                }
+                Some(None) => break,
+            }
+
+            count += 1;
+        }
+        assert!(coop_count >= 1);
+        assert_eq!(count, TASK_NUM);
+    }
+}
diff --git a/tokio/tests/tcp_peek.rs b/tokio/tests/tcp_peek.rs
index 03813c2e46c..b7120232ca4 100644
--- a/tokio/tests/tcp_peek.rs
+++ b/tokio/tests/tcp_peek.rs
@@ -15,7 +15,7 @@ async fn peek() {
     let addr = listener.local_addr().unwrap();
     let t = thread::spawn(move || assert_ok!(listener.accept()).0);
 
-    let left = net::TcpStream::connect(&addr).unwrap();
+    let left = net::TcpStream::connect(addr).unwrap();
     let mut right = t.join().unwrap();
     let _ = right.write(&[1, 2, 3, 4]).unwrap();
 
diff --git a/tokio/tests/tcp_stream.rs b/tokio/tests/tcp_stream.rs
index 453023fc51d..31fe3baa296 100644
--- a/tokio/tests/tcp_stream.rs
+++ b/tokio/tests/tcp_stream.rs
@@ -254,30 +254,34 @@ async fn create_pair() -> (TcpStream, TcpStream) {
     (client, server)
 }
 
-fn read_until_pending(stream: &mut TcpStream) {
+fn read_until_pending(stream: &mut TcpStream) -> usize {
     let mut buf = vec![0u8; 1024 * 1024];
+    let mut total = 0;
     loop {
         match stream.try_read(&mut buf) {
-            Ok(_) => (),
+            Ok(n) => total += n,
             Err(err) => {
                 assert_eq!(err.kind(), io::ErrorKind::WouldBlock);
                 break;
             }
         }
     }
+    total
 }
 
-fn write_until_pending(stream: &mut TcpStream) {
+fn write_until_pending(stream: &mut TcpStream) -> usize {
     let buf = vec![0u8; 1024 * 1024];
+    let mut total = 0;
     loop {
         match stream.try_write(&buf) {
-            Ok(_) => (),
+            Ok(n) => total += n,
             Err(err) => {
                 assert_eq!(err.kind(), io::ErrorKind::WouldBlock);
                 break;
             }
         }
     }
+    total
 }
 
 #[tokio::test]
@@ -357,3 +361,40 @@ async fn try_read_buf() {
         }
     }
 }
+
+// read_closed is a best effort event, so test only for no false positives.
+#[tokio::test]
+async fn read_closed() {
+    let (client, mut server) = create_pair().await;
+
+    let mut ready_fut = task::spawn(client.ready(Interest::READABLE));
+    assert_pending!(ready_fut.poll());
+
+    assert_ok!(server.write_all(b"ping").await);
+
+    let ready_event = assert_ok!(ready_fut.await);
+
+    assert!(!ready_event.is_read_closed());
+}
+
+// write_closed is a best effort event, so test only for no false positives.
+#[tokio::test]
+async fn write_closed() {
+    let (mut client, mut server) = create_pair().await;
+
+    // Fill the write buffer.
+    let write_size = write_until_pending(&mut client);
+    let mut ready_fut = task::spawn(client.ready(Interest::WRITABLE));
+    assert_pending!(ready_fut.poll());
+
+    // Drain the socket to make client writable.
+    let mut read_size = 0;
+    while read_size < write_size {
+        server.readable().await.unwrap();
+        read_size += read_until_pending(&mut server);
+    }
+
+    let ready_event = assert_ok!(ready_fut.await);
+
+    assert!(!ready_event.is_write_closed());
+}