[3.10] bpo-45021: Fix a hang in forked children (GH-28007) (GH-28480)
_global_shutdown_lock should be reinitialized in forked children
(cherry picked from commit 0bfa1106acfcddc03590e1f5d6789dbad3affe70)
Co-authored-by: nullptr <3621629+0x0L@users.noreply.github.com>
Automerge-Triggered-By: GH:gpshead
diff --git a/Lib/concurrent/futures/thread.py b/Lib/concurrent/futures/thread.py
index b7a2cac..51c942f 100644
--- a/Lib/concurrent/futures/thread.py
+++ b/Lib/concurrent/futures/thread.py
@@ -36,6 +36,12 @@ def _python_exit():
# See bpo-39812 for context.
threading._register_atexit(_python_exit)
+# At fork, reinitialize the `_global_shutdown_lock` lock in the child process
+if hasattr(os, 'register_at_fork'):
+ os.register_at_fork(before=_global_shutdown_lock.acquire,
+ after_in_child=_global_shutdown_lock._at_fork_reinit,
+ after_in_parent=_global_shutdown_lock.release)
+
class _WorkItem(object):
def __init__(self, future, fn, args, kwargs):
diff --git a/Lib/test/test_concurrent_futures.py b/Lib/test/test_concurrent_futures.py
index b0df12c..84209ca 100644
--- a/Lib/test/test_concurrent_futures.py
+++ b/Lib/test/test_concurrent_futures.py
@@ -911,6 +911,20 @@ def test_idle_thread_reuse(self):
self.assertEqual(len(executor._threads), 1)
executor.shutdown(wait=True)
+ @unittest.skipUnless(hasattr(os, 'register_at_fork'), 'need os.register_at_fork')
+ def test_hang_global_shutdown_lock(self):
+ # bpo-45021: _global_shutdown_lock should be reinitialized in the child
+ # process, otherwise it will never exit
+ def submit(pool):
+ pool.submit(submit, pool)
+
+ with futures.ThreadPoolExecutor(1) as pool:
+ pool.submit(submit, pool)
+
+ for _ in range(50):
+ with futures.ProcessPoolExecutor(1, mp_context=get_context('fork')) as workers:
+ workers.submit(tuple)
+
class ProcessPoolExecutorTest(ExecutorTest):