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Clarify some Git.execute kill_after_timeout limitations #1761

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merged 2 commits into from
Dec 10, 2023
Merged

Clarify some Git.execute kill_after_timeout limitations #1761

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f42a63b
Document more Git.execute kill_after_timeout limitations
EliahKagan Dec 10, 2023
2f017ac
Avoid making it look like kill_process works on Windows
EliahKagan Dec 10, 2023
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36 changes: 20 additions & 16 deletions git/cmd.py
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Original file line number Diff line number Diff line change
Expand Up @@ -879,11 +879,19 @@ def execute(
Specifies a timeout in seconds for the git command, after which the process
should be killed. This will have no effect if `as_process` is set to True.
It is set to None by default and will let the process run until the timeout
is explicitly specified. This feature is not supported on Windows. It's also
worth noting that `kill_after_timeout` uses SIGKILL, which can have negative
side effects on a repository. For example, stale locks in case of ``git gc``
could render the repository incapable of accepting changes until the lock is
manually removed.
is explicitly specified. Uses of this feature should be carefully
considered, due to the following limitations:

1. This feature is not supported at all on Windows.
2. Effectiveness may vary by operating system. ``ps --ppid`` is used to
enumerate child processes, which is available on most GNU/Linux systems
but not most others.
3. Deeper descendants do not receive signals, though they may sometimes
terminate as a consequence of their parent processes being killed.
4. `kill_after_timeout` uses ``SIGKILL``, which can have negative side
effects on a repository. For example, stale locks in case of ``git gc``
could render the repository incapable of accepting changes until the lock
is manually removed.

:param with_stdout:
If True, default True, we open stdout on the created process.
Expand Down Expand Up @@ -1007,11 +1015,9 @@ def execute(

def kill_process(pid: int) -> None:
"""Callback to kill a process."""
p = Popen(
["ps", "--ppid", str(pid)],
stdout=PIPE,
creationflags=PROC_CREATIONFLAGS,
)
if os.name == "nt":
raise AssertionError("Bug: This callback would be ineffective and unsafe on Windows, stopping.")
p = Popen(["ps", "--ppid", str(pid)], stdout=PIPE)
child_pids = []
if p.stdout is not None:
for line in p.stdout:
Expand All @@ -1020,18 +1026,16 @@ def kill_process(pid: int) -> None:
if local_pid.isdigit():
child_pids.append(int(local_pid))
try:
# Windows does not have SIGKILL, so use SIGTERM instead.
sig = getattr(signal, "SIGKILL", signal.SIGTERM)
os.kill(pid, sig)
os.kill(pid, signal.SIGKILL)
for child_pid in child_pids:
try:
os.kill(child_pid, sig)
os.kill(child_pid, signal.SIGKILL)
except OSError:
pass
kill_check.set() # Tell the main routine that the process was killed.
except OSError:
# It is possible that the process gets completed in the duration after timeout
# happens and before we try to kill the process.
# It is possible that the process gets completed in the duration after
# timeout happens and before we try to kill the process.
pass
return

Expand Down