[3.13] gh-135641: Fix flaky test_capi.test_lock_two_threads test case (gh-135642) (gh-135688)

miss-islington · colesbury · web-flow · commit 3bfb7da3d708 · 2025-06-18T18:47:59.000Z
The mutex may have the `_Py_HAS_PARKED` bit set. (cherry picked from commit 17ac393) Co-authored-by: Sam Gross <colesbury@gmail.com>
diff --git a/Modules/_testinternalcapi/test_lock.c b/Modules/_testinternalcapi/test_lock.c
@@ -57,7 +57,10 @@ lock_thread(void *arg)
     _Py_atomic_store_int(&test_data->started, 1);
 
     PyMutex_Lock(m);
-    assert(m->_bits == 1);
+    // gh-135641: in rare cases the lock may still have `_Py_HAS_PARKED` set
+    // (m->_bits == 3) due to bucket collisions in the parking lot hash table
+    // between this mutex and the `test_data.done` event.
+    assert(m->_bits == 1 || m->_bits == 3);
 
     PyMutex_Unlock(m);
     assert(m->_bits == 0);
