bpo-45274: Fix Thread._wait_for_tstate_lock() race condition (GH-28532) (GH-28580)
Fix a race condition in the Thread.join() method of the threading
module. If the function is interrupted by a signal and the signal
handler raises an exception, make sure that the thread remains in a
consistent state to prevent a deadlock.
(cherry picked from commit a22be4943c119fecf5433d999227ff78fc2e5741)
Co-authored-by: Victor Stinner <vstinner@python.org>
diff --git a/Lib/threading.py b/Lib/threading.py
index 766011f..f39da14 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -1100,11 +1100,24 @@ def _wait_for_tstate_lock(self, block=True, timeout=-1):
# If the lock is acquired, the C code is done, and self._stop() is
# called. That sets ._is_stopped to True, and ._tstate_lock to None.
lock = self._tstate_lock
- if lock is None: # already determined that the C code is done
+ if lock is None:
+ # already determined that the C code is done
assert self._is_stopped
- elif lock.acquire(block, timeout):
- lock.release()
- self._stop()
+ return
+
+ try:
+ if lock.acquire(block, timeout):
+ lock.release()
+ self._stop()
+ except:
+ if lock.locked():
+ # bpo-45274: lock.acquire() acquired the lock, but the function
+ # was interrupted with an exception before reaching the
+ # lock.release(). It can happen if a signal handler raises an
+ # exception, like CTRL+C which raises KeyboardInterrupt.
+ lock.release()
+ self._stop()
+ raise
@property
def name(self):