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Fix process group termination: always send SIGKILL after SIGTERM #151

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Fix process group termination: always send SIGKILL after SIGTERM #151

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c7a5c6c
Fix process group termination: always send SIGKILL after SIGTERM
Apr 7, 2026
04056f3
Fix formatting
Apr 7, 2026
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14 changes: 10 additions & 4 deletions lab/calls/call.py
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Original file line number Diff line number Diff line change
Expand Up @@ -242,13 +242,19 @@ def _update_cpu_time(self):

def _terminate_process_group(self):
"""Terminate the entire process group (parent and all children)."""
try:
pgid = os.getpgid(self.process.pid)
except (OSError, ProcessLookupError):
return

with contextlib.suppress(OSError, ProcessLookupError):
os.killpg(os.getpgid(self.process.pid), signal.SIGTERM)
os.killpg(pgid, signal.SIGTERM)

# Give it a moment to terminate gracefully.
time.sleep(1)
if self.process.poll() is None:
with contextlib.suppress(OSError, ProcessLookupError):
os.killpg(os.getpgid(self.process.pid), signal.SIGKILL)

with contextlib.suppress(OSError, ProcessLookupError):
os.killpg(pgid, signal.SIGKILL)
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@maltehelmert maltehelmert Apr 7, 2026

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What's the rationale for this change? I don't think it's good style to kill a process that we know has terminated. Is poll not reliable? If the process has terminated, it will be in zombie state here. Better to have it finish normally than kill it, I would say, if it has terminated in the one-second grace period.

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@TravisRiveraPetit TravisRiveraPetit Apr 7, 2026

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The problem is that we are currently using poll() on the leader process as a proxy for whether the whole process group has terminated.

Before, if the leader spawned child processes, it could happen that the leader exited after SIGTERM while some children were still running. In that case, poll() would return the leader’s exit code rather than None.


def _monitor_time_limits(self):
"""
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