New submission from Doug Zongker:
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
----------
components: Library (Lib)
files: fix.diff
keywords: patch
messages: 225208
nosy: dougz, pitrou
priority: normal
severity: normal
status: open
title: Occasional RuntimeError from Condition.notify
type: crash
versions: Python 3.4, Python 3.5
Added file: http://bugs.python.org/file36351/fix.diff
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<http://bugs.python.org/issue22185>
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