diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py index b8d310e4c99ff8..731e1046c000af 100644 --- a/Lib/test/test_threading.py +++ b/Lib/test/test_threading.py @@ -1381,6 +1381,33 @@ def test_native_id_after_fork(self): self.assertEqual(len(native_ids), 2) self.assertNotEqual(native_ids[0], native_ids[1]) + def test_stop_the_world_during_finalization(self): + # gh-137433: Test functions that trigger a stop-the-world in the free + # threading build concurrent with interpreter finalization. + script = """if True: + import gc + import sys + import threading + NUM_THREADS = 5 + b = threading.Barrier(NUM_THREADS + 1) + def run_in_bg(): + b.wait() + while True: + sys.setprofile(None) + gc.collect() + + for _ in range(NUM_THREADS): + t = threading.Thread(target=run_in_bg, daemon=True) + t.start() + + b.wait() + print("Exiting...") + """ + rc, out, err = assert_python_ok('-c', script) + self.assertEqual(rc, 0) + self.assertEqual(err, b"") + self.assertEqual(out.strip(), b"Exiting...") + class ThreadJoinOnShutdown(BaseTestCase): def _run_and_join(self, script): diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-08-13-13-39-02.gh-issue-137433.g6Atfz.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-08-13-13-39-02.gh-issue-137433.g6Atfz.rst new file mode 100644 index 00000000000000..0389cb0c735128 --- /dev/null +++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-08-13-13-39-02.gh-issue-137433.g6Atfz.rst @@ -0,0 +1,3 @@ +Fix a potential deadlock in the :term:`free threading` build when daemon +threads enable or disable profiling or tracing while the main thread is +shutting down the interpreter. diff --git a/Python/parking_lot.c b/Python/parking_lot.c index e896dea02712f2..0ffea97b079943 100644 --- a/Python/parking_lot.c +++ b/Python/parking_lot.c @@ -342,7 +342,19 @@ _PyParkingLot_Park(const void *addr, const void *expected, size_t size, enqueue(bucket, addr, &wait); _PyRawMutex_Unlock(&bucket->mutex); - int res = _PySemaphore_Wait(&wait.sema, timeout_ns, detach); + PyThreadState *tstate = NULL; + if (detach) { + tstate = _PyThreadState_GET(); + if (tstate && _PyThreadState_IsAttached(tstate)) { + // Only detach if we are attached + PyEval_ReleaseThread(tstate); + } + else { + tstate = NULL; + } + } + + int res = _PySemaphore_Wait(&wait.sema, timeout_ns, 0); if (res == Py_PARK_OK) { goto done; } @@ -354,7 +366,7 @@ _PyParkingLot_Park(const void *addr, const void *expected, size_t size, // Another thread has started to unpark us. Wait until we process the // wakeup signal. do { - res = _PySemaphore_Wait(&wait.sema, -1, detach); + res = _PySemaphore_Wait(&wait.sema, -1, 0); } while (res != Py_PARK_OK); goto done; } @@ -366,6 +378,9 @@ _PyParkingLot_Park(const void *addr, const void *expected, size_t size, done: _PySemaphore_Destroy(&wait.sema); + if (tstate) { + PyEval_AcquireThread(tstate); + } return res; } diff --git a/Python/pystate.c b/Python/pystate.c index b7da4e981ac1eb..6859dbc9a7f469 100644 --- a/Python/pystate.c +++ b/Python/pystate.c @@ -2345,13 +2345,15 @@ stop_the_world(struct _stoptheworld_state *stw) { _PyRuntimeState *runtime = &_PyRuntime; - PyMutex_Lock(&stw->mutex); + // gh-137433: Acquire the rwmutex first to avoid deadlocks with daemon + // threads that may hang when blocked on lock acquisition. if (stw->is_global) { _PyRWMutex_Lock(&runtime->stoptheworld_mutex); } else { _PyRWMutex_RLock(&runtime->stoptheworld_mutex); } + PyMutex_Lock(&stw->mutex); HEAD_LOCK(runtime); stw->requested = 1; @@ -2417,13 +2419,13 @@ start_the_world(struct _stoptheworld_state *stw) } stw->requester = NULL; HEAD_UNLOCK(runtime); + PyMutex_Unlock(&stw->mutex); if (stw->is_global) { _PyRWMutex_Unlock(&runtime->stoptheworld_mutex); } else { _PyRWMutex_RUnlock(&runtime->stoptheworld_mutex); } - PyMutex_Unlock(&stw->mutex); } #endif // Py_GIL_DISABLED