fix: Explicitly attach the event loop to the child watcher (#50)

changes/50.fix.md

@@ -0,0 +1 @@
+Explicitly attach the event loop to the `PidfdChildWatcher` when first initialized

src/aiotools/server.py

@@ -249,16 +249,18 @@ def helper(*args, **kwargs):
 main = _main_ctxmgr
 
 
-def setup_child_watcher():
+def setup_child_watcher(loop: asyncio.AbstractEventLoop) -> None:
     try:
         asyncio.get_child_watcher()
         if hasattr(asyncio, 'PidfdChildWatcher'):
-            asyncio.set_child_watcher(asyncio.PidfdChildWatcher())
+            watcher = asyncio.PidfdChildWatcher()
+            asyncio.set_child_watcher(watcher)
+            watcher.attach_loop(loop)
     except NotImplementedError:
         pass  # for uvloop
 
 
-async def cancel_all_tasks():
+async def cancel_all_tasks() -> None:
     loop = get_running_loop()
     cancelled_tasks = []
     for task in all_tasks():
@@ -289,7 +291,7 @@ def _worker_main(
 ) -> int:
     loop = asyncio.new_event_loop()
     asyncio.set_event_loop(loop)
-    setup_child_watcher()
+    setup_child_watcher(loop)
     interrupted = asyncio.Event()
     ctx = worker_actxmgr(loop, proc_idx, args)
     if _cv_available:
@@ -551,7 +553,7 @@ def noop_main_ctxmgr():
     main_future = main_loop.create_future()
 
     # to make subprocess working in child threads
-    setup_child_watcher()
+    setup_child_watcher(main_loop)
 
     # build a main-to-worker interrupt channel using signals
     def handle_stop_signal(signum: signal.Signals) -> None: