gh-94732: Fix KeyboardInterrupt race in asyncio run_forever() (#97765)

hetmankp · web-flow · commit 3a49dbb98ccc · 2022-10-03T13:34:35.000-07:00
Ensure that the event loop's `_thread_id` attribute and the asyncgen hooks set by `sys.set_asyncgen_hooks()` are always restored no matter where a KeyboardInterrupt exception is raised.
diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
@@ -606,12 +606,13 @@ def run_forever(self):
         self._check_closed()
         self._check_running()
         self._set_coroutine_origin_tracking(self._debug)
-        self._thread_id = threading.get_ident()
 
         old_agen_hooks = sys.get_asyncgen_hooks()
-        sys.set_asyncgen_hooks(firstiter=self._asyncgen_firstiter_hook,
-                               finalizer=self._asyncgen_finalizer_hook)
         try:
+            self._thread_id = threading.get_ident()
+            sys.set_asyncgen_hooks(firstiter=self._asyncgen_firstiter_hook,
+                                   finalizer=self._asyncgen_finalizer_hook)
+
             events._set_running_loop(self)
             while True:
                 self._run_once()
