Issue 22185: Occasional RuntimeError from Condition.notify (original) (raw)

Created on 2014-08-11 23:47 by dougz, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Messages (5)
msg225208 - (view)	Author: Doug Zongker (dougz) *	Date: 2014-08-11 23:47
Condition.wait() modifies self._waiters without holding the lock (when a wait with timeout times out without the condition being notified). If this happens to occur in between construction of the _islice and _deque objects in Condition.notify(): def notify(self, n=1): [...] all_waiters = self._waiters waiters_to_notify = _deque(_islice(all_waiters, n)) then the result is a RuntimeError exception: File "/usr/lib/python3.4/threading.py", line 358, in notify_all self.notify(len(self._waiters)) File "/usr/lib/python3.4/threading.py", line 341, in notify waiters_to_notify = _deque(_islice(all_waiters, n)) RuntimeError: deque mutated during iteration (I have a server which makes extensive use of conditions on which this happens about once a day.) This patch fixes this bug by moving wait()'s modification of self._waiters to be inside the lock, as suggested by Antoine Pitrou here: http://bugs.python.org/issue17385#msg183875
msg225213 - (view)	Author: Tim Peters (tim.peters) *	Date: 2014-08-12 00:18
+1. I agree it's a bug, that the diagnosis is correct, and that the patch will fix it :-)
msg226068 - (view)	Author: Doug Zongker (dougz) *	Date: 2014-08-29 17:18
So, what happens now? What do I need to do to make progress on this?
msg226088 - (view)	Author: Roundup Robot (python-dev)	Date: 2014-08-29 21:27
New changeset 4cce39cfe46c by Antoine Pitrou in branch '3.4': Issue #22185: Fix an occasional RuntimeError in threading.Condition.wait() caused by mutation of the waiters queue without holding the lock. http://hg.python.org/cpython/rev/4cce39cfe46c New changeset 78a38f8bd5d9 by Antoine Pitrou in branch 'default': Issue #22185: Fix an occasional RuntimeError in threading.Condition.wait() caused by mutation of the waiters queue without holding the lock. http://hg.python.org/cpython/rev/78a38f8bd5d9
msg226089 - (view)	Author: Antoine Pitrou (pitrou) *	Date: 2014-08-29 21:28
It only needed someone to push your patch, which I just did. Thank you very much Doug, your contribution is appreciated!