pythongh-117657: Fix TSAN race in QSBR assertion (python#119887)

Due to a limitation in TSAN, all reads from `PyThreadState.state` must be atomic to avoid reported races.
estyxx · Jul 17, 2024 · e04e145 · e04e145
1 parent 8095f62
commit e04e145
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Showing 2 changed files with 2 additions and 3 deletions.
diff --git a/Python/qsbr.c b/Python/qsbr.c
@@ -160,7 +160,8 @@ qsbr_poll_scan(struct _qsbr_shared *shared)
 bool
 _Py_qsbr_poll(struct _qsbr_thread_state *qsbr, uint64_t goal)
 {
-    assert(_PyThreadState_GET()->state == _Py_THREAD_ATTACHED);
+    assert(_Py_atomic_load_int_relaxed(&_PyThreadState_GET()->state) == _Py_THREAD_ATTACHED);
+
     if (_Py_qbsr_goal_reached(qsbr, goal)) {
         return true;
     }

diff --git a/Tools/tsan/suppressions_free_threading.txt b/Tools/tsan/suppressions_free_threading.txt
@@ -75,8 +75,6 @@ race_top:_PyFrame_GetCode
 race_top:_PyFrame_Initialize
 race_top:PyInterpreterState_ThreadHead
 race_top:_PyObject_TryGetInstanceAttribute
-race_top:_Py_qsbr_unregister
-race_top:_Py_qsbr_poll
 race_top:PyThreadState_Next
 race_top:Py_TYPE
 race_top:PyUnstable_InterpreterFrame_GetLine