From 43f846e10de6a1c20f1e1648187d996cbaeba14c Mon Sep 17 00:00:00 2001 From: elfstrom Date: Tue, 3 Oct 2023 23:59:49 +0200 Subject: [PATCH] gh-109917: Fix test instability in test_concurrent_futures (GH-110306) The test had an instability issue due to the ordering of the dummy queue operation and the real wakeup pipe operations. Both primitives are thread safe but not done atomically as a single update and may interleave arbitrarily. With the old order of operations this can lead to an incorrect state where the dummy queue is full but the wakeup pipe is empty. By swapping the order in clear() I think this can no longer happen in any possible operation interleaving (famous last words). (cherry picked from commit a376a72bd92cd7c9930467dd1aba40045fb75e3b) Co-authored-by: elfstrom --- Lib/test/test_concurrent_futures/test_deadlock.py | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/Lib/test/test_concurrent_futures/test_deadlock.py b/Lib/test/test_concurrent_futures/test_deadlock.py index 7ede95d5ed3422..1db4cd009926b9 100644 --- a/Lib/test/test_concurrent_futures/test_deadlock.py +++ b/Lib/test/test_concurrent_futures/test_deadlock.py @@ -284,11 +284,12 @@ def wakeup(self): super().wakeup() def clear(self): + super().clear() try: while True: self._dummy_queue.get_nowait() except queue.Empty: - super().clear() + pass with (unittest.mock.patch.object(futures.process._ExecutorManagerThread, 'run', mock_run),