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gh-105829: Fix concurrent.futures.ProcessPoolExecutor deadlock (#108513)

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This fixes issue #105829, https://github.com/python/cpython/issues/105829

Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: Antoine Pitrou <antoine@python.org>
Co-authored-by: Chris Withers <chris@withers.org>
Co-authored-by: Thomas Moreau <thomas.moreau.2010@gmail.com>
This commit is contained in:
elfstrom 2023-09-22 14:55:56 +02:00 • committed by GitHub
parent e94a2232ea
commit 405b06375a
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3 changed files with 87 additions and 4 deletions
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18
Lib/concurrent/futures/process.py
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@ -71,6 +71,11 @@ class _ThreadWakeup:
self._reader, self._writer = mp.Pipe(duplex=False)
def close(self):
# Please note that we do not take the shutdown lock when
# calling clear() (to avoid deadlocking) so this method can
# only be called safely from the same thread as all calls to
# clear() even if you hold the shutdown lock. Otherwise we
# might try to read from the closed pipe.
if not self._closed:
self._closed = True
self._writer.close()
@ -426,8 +431,12 @@ class _ExecutorManagerThread(threading.Thread):
elif wakeup_reader in ready:
is_broken = False
with self.shutdown_lock:
self.thread_wakeup.clear()
# No need to hold the _shutdown_lock here because:
# 1. we're the only thread to use the wakeup reader
# 2. we're also the only thread to call thread_wakeup.close()
# 3. we want to avoid a possible deadlock when both reader and writer
# would block (gh-105829)
self.thread_wakeup.clear()
return result_item, is_broken, cause
@ -717,7 +726,10 @@ class ProcessPoolExecutor(_base.Executor):
# as it could result in a deadlock if a worker process dies with the
# _result_queue write lock still acquired.
#
# _shutdown_lock must be locked to access _ThreadWakeup.
# _shutdown_lock must be locked to access _ThreadWakeup.close() and
# .wakeup(). Care must also be taken to not call clear or close from
# more than one thread since _ThreadWakeup.clear() is not protected by
# the _shutdown_lock
self._executor_manager_thread_wakeup = _ThreadWakeup()
# Create communication channels for the executor