From 47186880d605cb9723e5753bab81589aa53768d7 Mon Sep 17 00:00:00 2001
From: Sam Gross <colesbury@gmail.com>
Date: Tue, 17 Jun 2025 20:36:01 +0000
Subject: [PATCH] gh-135641: Fix flaky test_lock_two_threads test case

The mutex may have the _Py_HAS_PARKED bit set in rare cases.
---
 Modules/_testinternalcapi/test_lock.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Modules/_testinternalcapi/test_lock.c b/Modules/_testinternalcapi/test_lock.c
index 8d678412fe7179..8d8cb992b0e07f 100644
--- 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);