From e7268d5bd05784d779b4a858a1ed43c4fe9990be Mon Sep 17 00:00:00 2001 From: Sam Gross Date: Mon, 20 Oct 2025 09:58:05 -0400 Subject: [PATCH] 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. (cherry picked from commit f11ec6e643f54f4ee698f7dfc878812a315f2af4) Co-authored-by: Sam Gross --- Modules/_testinternalcapi/test_lock.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) 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);