00371: Revert "bpo-1596321: Fix threading._shutdown() for the main thread (pythonGH-28549) (pythonGH-28589)"

This reverts commit 38c6773. It
introduced regression causing FreeIPA's tests to fail.

For more info see:
https://bodhi.fedoraproject.org/updates/FEDORA-2021-e152ce5f31
GrahamDumpleton/mod_wsgi#730

Author: hrnciar

Lib/test/test_threading.py

@@ -1056,39 +1056,6 @@ def noop(): pass
             threading.Thread(target=noop).start()
             # Thread.join() is not called
 
-    def test_import_from_another_thread(self):
-        # bpo-1596321: If the threading module is first import from a thread
-        # different than the main thread, threading._shutdown() must handle
-        # this case without logging an error at Python exit.
-        code = textwrap.dedent('''
-            import _thread
-            import sys
-
-            event = _thread.allocate_lock()
-            event.acquire()
-
-            def import_threading():
-                import threading
-                event.release()
-
-            if 'threading' in sys.modules:
-                raise Exception('threading is already imported')
-
-            _thread.start_new_thread(import_threading, ())
-
-            # wait until the threading module is imported
-            event.acquire()
-            event.release()
-
-            if 'threading' not in sys.modules:
-                raise Exception('threading is not imported')
-
-            # don't wait until the thread completes
-        ''')
-        rc, out, err = assert_python_ok("-c", code)
-        self.assertEqual(out, b'')
-        self.assertEqual(err, b'')
-
     def test_start_new_thread_at_exit(self):
         code = """if 1:
             import atexit

Lib/threading.py

@@ -1616,32 +1616,23 @@ def _shutdown():
 
     global _SHUTTING_DOWN
     _SHUTTING_DOWN = True
+    # Main thread
+    tlock = _main_thread._tstate_lock
+    # The main thread isn't finished yet, so its thread state lock can't have
+    # been released.
+    assert tlock is not None
+    if tlock.locked():
+        # It should have been released already by
+        # _PyInterpreterState_SetNotRunningMain(), but there may be
+        # embedders that aren't calling that yet.
+        tlock.release()
+    _main_thread._stop()
 
     # Call registered threading atexit functions before threads are joined.
     # Order is reversed, similar to atexit.
     for atexit_call in reversed(_threading_atexits):
         atexit_call()
 
-    # Main thread
-    if _main_thread.ident == get_ident():
-        tlock = _main_thread._tstate_lock
-        # The main thread isn't finished yet, so its thread state lock can't
-        # have been released.
-        assert tlock is not None
-        if tlock.locked():
-            # It should have been released already by
-            # _PyInterpreterState_SetNotRunningMain(), but there may be
-            # embedders that aren't calling that yet.
-            tlock.release()
-        _main_thread._stop()
-    else:
-        # bpo-1596321: _shutdown() must be called in the main thread.
-        # If the threading module was not imported by the main thread,
-        # _main_thread is the thread which imported the threading module.
-        # In this case, ignore _main_thread, similar behavior than for threads
-        # spawned by C libraries or using _thread.start_new_thread().
-        pass
-
     # Join all non-deamon threads
     while True:
         with _shutdown_locks_lock: