[3.9] GH-100892: Fix race in clearing `threading.local` (GH-100922) (#100939)

[3.9] [3.10] GH-100892: Fix race in clearing `threading.local` (GH-100922).
(cherry picked from commit 762745a124cbc297cf2fe6f3ec9ca1840bb2e873)

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>.
(cherry picked from commit 683e9fe30ecd024f5508b2a33316752870100a96)

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/Lib/test/test_threading_local.py b/Lib/test/test_threading_local.py
index 5ddb8c4..8b24e3a 100644
--- a/Lib/test/test_threading_local.py
+++ b/Lib/test/test_threading_local.py
@@ -193,6 +193,22 @@ class BaseLocalTest:
         self.assertIsNone(wr())
 
 
+    def test_threading_local_clear_race(self):
+        # See https://github.com/python/cpython/issues/100892
+
+        try:
+            import _testcapi
+        except ImportError:
+            unittest.skip("requires _testcapi")
+
+        _testcapi.call_in_temporary_c_thread(lambda: None, False)
+
+        for _ in range(1000):
+            _ = threading.local()
+
+        _testcapi.join_temporary_c_thread()
+
+
 class ThreadLocalTest(unittest.TestCase, BaseLocalTest):
     _local = _thread._local