GH-66285: fix forking in `asyncio` (#99539)

`asyncio` now does not shares event loop and signal wakeupfd in forked processes.

1 files changed, 9 insertions, 0 deletions

diff --git a/Lib/asyncio/events.py b/Lib/asyncio/events.py
index a327ba54a32..39a01048b4c 100644
--- a/Lib/asyncio/events.py
+++ b/Lib/asyncio/events.py
@@ -17,6 +17,7 @@ import socket
 import subprocess
 import sys
 import threading
+import signal
 
 from . import format_helpers
 
@@ -665,6 +666,14 @@ class BaseDefaultEventLoopPolicy(AbstractEventLoopPolicy):
 
     def __init__(self):
         self._local = self._Local()
+        if hasattr(os, 'fork'):
+            def on_fork():
+                # Reset the loop and wakeupfd in the forked child process.
+                self._local = self._Local()
+                signal.set_wakeup_fd(-1)
+
+            os.register_at_fork(after_in_child=on_fork)
+
 
     def get_event_loop(self):
         """Get the event loop for the current context.