[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

STINNER Victor added the comment: Hum, my commit was not reported in the issue: commit da6d305b6fcd49ba1224b1fd2131d7648a5be6b9 Author: Victor Stinner Date: Thu Jun 22 02:09:40 2017 +0200 bpo-8799: Reduce timing sensitivity of condition test by explicitly

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

STINNER Victor added the comment: > In Python 3 the test was failed if decrease the sleep time in _wait() to > 0.001. Patched test no longer fail for any small sleep intervals. I used sleep(1e-9), 1 nanosecond, for my tests :-) I confirm that I'm unable to reproduce the bug on 2.7 and master

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Serhiy Storchaka added the comment: In Python 3 the test was failed if decrease the sleep time in _wait() to 0.001. Patched test no longer fail for any small sleep intervals. -- resolution: -> fixed stage: -> resolved status: open -> closed versions: +Python 3.5, Python 3.6, Python

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Serhiy Storchaka added the comment: New changeset 7709b4d57b433ef027a2e7e63b4cab3fc9ad910d by Serhiy Storchaka in branch '2.7': [2.7] bpo-30727: Fix a race condition in test_threading. (GH-2334). (#2353) https://github.com/python/cpython/commit/7709b4d57b433ef027a2e7e63b4cab3fc9ad910d

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Serhiy Storchaka added the comment: New changeset e2aec8e691d8acb08373889d9af48a5b1d03b689 by Serhiy Storchaka in branch '3.5': [3.5] bpo-30727: Fix a race condition in test_threading. (GH-2334) (#2352) https://github.com/python/cpython/commit/e2aec8e691d8acb08373889d9af48a5b1d03b689

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Serhiy Storchaka added the comment: New changeset c1d5345679eaa5fccd719b1c130140eecc8ba4c8 by Serhiy Storchaka in branch '3.6': [3.6] bpo-30727: Fix a race condition in test_threading. (GH-2334) (#2351) https://github.com/python/cpython/commit/c1d5345679eaa5fccd719b1c130140eecc8ba4c8

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Changes by Serhiy Storchaka : -- pull_requests: +2399 ___ Python tracker ___ ___

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Changes by Serhiy Storchaka : -- pull_requests: +2398 ___ Python tracker ___ ___

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Changes by Serhiy Storchaka : -- pull_requests: +2397 ___ Python tracker ___ ___

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Serhiy Storchaka added the comment: New changeset 32cb968a2edd482891c33b6f2ebae10f1d305424 by Serhiy Storchaka in branch 'master': bpo-30727: Fix a race condition in test_threading. (#2334) https://github.com/python/cpython/commit/32cb968a2edd482891c33b6f2ebae10f1d305424 --

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Serhiy Storchaka added the comment: Actually this approach already is used in this test. PR 2334 uses it to ensure all workers into cond.wait(). -- ___ Python tracker

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Changes by Serhiy Storchaka : -- pull_requests: +2378 ___ Python tracker ___ ___

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Serhiy Storchaka added the comment: I still didn't see a code, but perhaps we could use a spin-lock. Every child thread increases the global counter, and the main thread waits until the counter equal to the number of child threads (sleeping for short time in a loop) before calling notify().

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Antoine Pitrou added the comment: Yes, the whole reason I wrote the tests like this is to avoid depending on Python synchronization primitives inside the tests for Python synchronization primitives. -- ___ Python tracker

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Kristján Valur Jónsson added the comment: My favorite topic :) You could use threading.Barrier() which is designed to synchronize N threads doing this kind of lock-step processing. The problem is that the Barrier() is implemented using Condition variables, so for unit-testing, Condition

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

STINNER Victor added the comment: It's getting late here, so I chose to first backport the commit 020af2a2bc4708215360a3793b5a1790e15d05dd to Python 2.7, to reduce the likehood of this bug on 2.7 buildbots. -- pull_requests: +2372 ___ Python

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

STINNER Victor added the comment: The bug occurs when notify(n) is called while less than n threads are waiting in cond.wait(): when some threads didn't reach cond.wait() yet. The synchronization code is very fragile and depends on time. The issue was worked again in the master banch by

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

STINNER Victor added the comment: See also bpo-8799 "Hang in lib/test/test_threading.py" and the commit 020af2a2bc4708215360a3793b5a1790e15d05dd which added two _wait() calls to ConditionTests._check_notify(). -- ___ Python tracker

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

STINNER Victor added the comment: notify_bug.py: script close totest.test_threading.ConditionTests.test_notify() but different: * _wait() sleeps 1 nanosecond rather than 10 ms * log many messages into stdout (file descriptor 1) using os.write() It's quite easy to reproduce the bug with this

[issue30727] [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7

Changes by STINNER Victor : -- title: [2.7] test_threading.ConditionTests.test_notify() hangs randomly on FreeBSD on Python 2.7 -> [2.7] test_threading.ConditionTests.test_notify() hangs randomly on Python 2.7 ___ Python