https://github.com/python/cpython/commit/388e023fe1197c1ffed374520ed45df4ac72b8f5
commit: 388e023fe1197c1ffed374520ed45df4ac72b8f5
branch: main
author: saisneha196 <[email protected]>
committer: cjw296 <[email protected]>
date: 2026-05-21T08:38:07+01:00
summary:
gh-150175: Fix ThreadingMock call_count race condition (#150176)
ThreadingMock._increment_mock_call() was not thread-safe.
Multiple threads calling the mock simultaneously could lose
increments due to race conditions on call_count and other
attributes.
Fix by overriding _increment_mock_call in ThreadingMixin
and wrapping it with the existing _mock_calls_events_lock.
files:
A Misc/NEWS.d/next/Library/2026-05-21-11-25-58.gh-issue-150175.8H4Caz.rst
M Lib/unittest/mock.py
diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
index 16f3699e89e77d..56cdc37942d65d 100644
--- a/Lib/unittest/mock.py
+++ b/Lib/unittest/mock.py
@@ -3113,6 +3113,10 @@ def _mock_call(self, *args, **kwargs):
return ret_value
+ def _increment_mock_call(self, /, *args, **kwargs):
+ with self._mock_calls_events_lock:
+ super()._increment_mock_call(*args, **kwargs)
+
def wait_until_called(self, *, timeout=_timeout_unset):
"""Wait until the mock object is called.
diff --git
a/Misc/NEWS.d/next/Library/2026-05-21-11-25-58.gh-issue-150175.8H4Caz.rst
b/Misc/NEWS.d/next/Library/2026-05-21-11-25-58.gh-issue-150175.8H4Caz.rst
new file mode 100644
index 00000000000000..80fc80d4d50a63
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-05-21-11-25-58.gh-issue-150175.8H4Caz.rst
@@ -0,0 +1,3 @@
+Fix race condition in :class:`unittest.mock.ThreadingMock` where
+concurrent calls could lose increments to ``call_count`` and other
+attributes due to a missing lock in ``_increment_mock_call``.
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