https://github.com/python/cpython/commit/f11ec6e643f54f4ee698f7dfc878812a315f2af4
commit: f11ec6e643f54f4ee698f7dfc878812a315f2af4
branch: main
author: Sam Gross <[email protected]>
committer: colesbury <[email protected]>
date: 2025-10-20T09:58:05-04:00
summary:
gh-140263: Fix data race in test_lock_two_threads (gh-140264)
Clang-20 detects a data race between the unlock and the non-atomic
read of the lock state. Use a relaxed load for the assertion to avoid
the race.
files:
M Modules/_testinternalcapi/test_lock.c
diff --git a/Modules/_testinternalcapi/test_lock.c
b/Modules/_testinternalcapi/test_lock.c
index 8d8cb992b0e07f..ded76ca9fe6819 100644
--- a/Modules/_testinternalcapi/test_lock.c
+++ b/Modules/_testinternalcapi/test_lock.c
@@ -91,7 +91,8 @@ test_lock_two_threads(PyObject *self, PyObject *obj)
} while (v != 3 && iters < 200);
// both the "locked" and the "has parked" bits should be set
- assert(test_data.m._bits == 3);
+ v = _Py_atomic_load_uint8_relaxed(&test_data.m._bits);
+ assert(v == 3);
PyMutex_Unlock(&test_data.m);
PyEvent_Wait(&test_data.done);
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