gh-114177: avoid calling connection lost callbacks when loop is already closed in asyncio subprocess (#134508)

Lib/asyncio/base_subprocess.py

@@ -104,7 +104,12 @@ class BaseSubprocessTransport(transports.SubprocessTransport):
         for proto in self._pipes.values():
             if proto is None:
                 continue
-            proto.pipe.close()
+            # See gh-114177
+            # skip closing the pipe if loop is already closed
+            # this can happen e.g. when loop is closed immediately after
+            # process is killed
+            if self._loop and not self._loop.is_closed():
+                proto.pipe.close()
 
         if (self._proc is not None and
                 # has the child process finished?

Misc/NEWS.d/next/Library/2025-05-22-13-10-32.gh-issue-114177.3TYUJ3.rst

@@ -0,0 +1 @@
+Fix :mod:`asyncio` to not close subprocess pipes which would otherwise error out when the event loop is already closed.