gh-111358: Fix timeout behaviour in BaseEventLoop.shutdown_default_executor (#115622)

Lib/asyncio/base_events.py

@@ -45,6 +45,7 @@ from . import protocols
 from . import sslproto
 from . import staggered
 from . import tasks
+from . import timeouts
 from . import transports
 from . import trsock
 from .log import logger
@@ -598,23 +599,24 @@ class BaseEventLoop(events.AbstractEventLoop):
         thread = threading.Thread(target=self._do_shutdown, args=(future,))
         thread.start()
         try:
-            await future
-        finally:
-            thread.join(timeout)
-
-        if thread.is_alive():
+            async with timeouts.timeout(timeout):
+                await future
+        except TimeoutError:
             warnings.warn("The executor did not finishing joining "
-                             f"its threads within {timeout} seconds.",
-                             RuntimeWarning, stacklevel=2)
+                          f"its threads within {timeout} seconds.",
+                          RuntimeWarning, stacklevel=2)
             self._default_executor.shutdown(wait=False)
+        else:
+            thread.join()
 
     def _do_shutdown(self, future):
         try:
             self._default_executor.shutdown(wait=True)
             if not self.is_closed():
-                self.call_soon_threadsafe(future.set_result, None)
+                self.call_soon_threadsafe(futures._set_result_unless_cancelled,
+                                          future, None)
         except Exception as ex:
-            if not self.is_closed():
+            if not self.is_closed() and not future.cancelled():
                 self.call_soon_threadsafe(future.set_exception, ex)
 
     def _check_running(self):