[3.13] gh-132542: Set native thread ID after fork (GH-132701) (GH-134361)

(cherry picked from commit 6b73502313)

Lib/test/test_threading.py

@@ -1208,6 +1208,34 @@ def f():
         self.assertEqual(err, b'')
 
 
+    @skip_unless_reliable_fork
+    def test_native_id_after_fork(self):
+        script = """if True:
+            import threading
+            import os
+            from test import support
+
+            parent_thread_native_id = threading.current_thread().native_id
+            print(parent_thread_native_id, flush=True)
+            assert parent_thread_native_id == threading.get_native_id()
+            childpid = os.fork()
+            if childpid == 0:
+                print(threading.current_thread().native_id, flush=True)
+                assert threading.current_thread().native_id == threading.get_native_id()
+            else:
+                try:
+                    assert parent_thread_native_id == threading.current_thread().native_id
+                    assert parent_thread_native_id == threading.get_native_id()
+                finally:
+                    support.wait_process(childpid, exitcode=0)
+            """
+        rc, out, err = assert_python_ok('-c', script)
+        self.assertEqual(rc, 0)
+        self.assertEqual(err, b"")
+        native_ids = out.strip().splitlines()
+        self.assertEqual(len(native_ids), 2)
+        self.assertNotEqual(native_ids[0], native_ids[1])
+
 class ThreadJoinOnShutdown(BaseTestCase):
 
     def _run_and_join(self, script):