[3.13] gh-117657: Fix TSAN race in QSBR assertion (GH-119887) (#119904)

Due to a limitation in TSAN, all reads from `PyThreadState.state` must be
atomic to avoid reported races.
(cherry picked from commit 90ec19fd33e2452902b9788d4821f1fbf6542304)

Co-authored-by: Sam Gross <colesbury@gmail.com>

diff --git a/Python/qsbr.c b/Python/qsbr.c
index 9cbce9044e2941c6ccac45ac08dde16211df247e..a7321154a62ffc837f343c2a77a1f754cb894649 100644 (file)
--- 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
index 27568c34e1689e6c7a80257284fa5f80d7a99f20..dbb0aacb7ed9cd596ffcd405c25f19fb3f33489a 100644 (file)
--- a/Tools/tsan/suppressions_free_threading.txt
+++ b/Tools/tsan/suppressions_free_threading.txt
@@ -76,8 +76,6 @@ 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