[3.10] GH-100892: Fix race in clearing `threading.local` (GH-100922). (#100938)

(cherry picked from commit 762745a124cbc297cf2fe6f3ec9ca1840bb2e873)

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

1 files changed, 13 insertions, 0 deletions

diff --git a/Lib/test/test_threading_local.py b/Lib/test/test_threading_local.py
index 13facb5..f1ef30e 100644
--- a/Lib/test/test_threading_local.py
+++ b/Lib/test/test_threading_local.py
@@ -3,6 +3,7 @@ import unittest
 from doctest import DocTestSuite
 from test import support
 from test.support import threading_helper
+from test.support.import_helper import import_module
 import weakref
 import gc
 
@@ -194,6 +195,18 @@ class BaseLocalTest:
         self.assertIsNone(wr())
 
 
+    def test_threading_local_clear_race(self):
+        # See https://github.com/python/cpython/issues/100892
+
+        _testcapi = import_module('_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