pythonGH-96827: Don't touch closed loops from executor threads (pythonGH-96837)

* When chaining futures, skip callback if loop closed.
* When shutting down an executor, don't wake a closed loop.
(cherry picked from commit e9d6376)

Co-authored-by: Guido van Rossum <[email protected]>

Author: gvanrossum

Lib/asyncio/base_events.py

@@ -573,9 +573,11 @@ async def shutdown_default_executor(self):
     def _do_shutdown(self, future):
         try:
             self._default_executor.shutdown(wait=True)
-            self.call_soon_threadsafe(future.set_result, None)
+            if not self.is_closed():
+                self.call_soon_threadsafe(future.set_result, None)
         except Exception as ex:
-            self.call_soon_threadsafe(future.set_exception, ex)
+            if not self.is_closed():
+                self.call_soon_threadsafe(future.set_exception, ex)
 
     def _check_running(self):
         if self.is_running():

Lib/asyncio/futures.py

@@ -396,6 +396,8 @@ def _call_set_state(source):
         if dest_loop is None or dest_loop is source_loop:
             _set_state(destination, source)
         else:
+            if dest_loop.is_closed():
+                return
             dest_loop.call_soon_threadsafe(_set_state, destination, source)
 
     destination.add_done_callback(_call_check_cancel)

Misc/NEWS.d/next/Library/2022-09-30-15-56-20.gh-issue-96827.lzy1iw.rst

@@ -0,0 +1 @@
+Avoid spurious tracebacks from :mod:`asyncio` when default executor cleanup is delayed until after the event loop is closed (e.g. as the result of a keyboard interrupt).