https://github.com/python/cpython/commit/728e4a075e3dae7e04edf90ad137a35073deb141
commit: 728e4a075e3dae7e04edf90ad137a35073deb141
branch: main
author: Kumar Aditya <[email protected]>
committer: kumaraditya303 <[email protected]>
date: 2026-03-10T12:11:12Z
summary:
gh-142651: use `NonCallableMock._lock` for thread safety of `call_count`
(#142922)
files:
M Lib/unittest/mock.py
diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
index 34fd49bf56fbb6..64a01a0b713c61 100644
--- a/Lib/unittest/mock.py
+++ b/Lib/unittest/mock.py
@@ -1184,10 +1184,16 @@ def _increment_mock_call(self, /, *args, **kwargs):
# handle call_args
# needs to be set here so assertions on call arguments pass before
# execution in the case of awaited calls
- _call = _Call((args, kwargs), two=True)
- self.call_args = _call
- self.call_args_list.append(_call)
- self.call_count = len(self.call_args_list)
+ with NonCallableMock._lock:
+ # Lock is used here so that call_args_list and call_count are
+ # set atomically otherwise it is possible that by the time
call_count
+ # is set another thread may have appended to call_args_list.
+ # The rest of this function relies on list.append being atomic and
+ # skips locking.
+ _call = _Call((args, kwargs), two=True)
+ self.call_args = _call
+ self.call_args_list.append(_call)
+ self.call_count = len(self.call_args_list)
# initial stuff for method_calls:
do_method_calls = self._mock_parent is not None
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