GH-98023: Change default child watcher to PidfdChildWatcher on supported systems (#98024)

1 files changed, 15 insertions, 1 deletions

diff --git a/Lib/asyncio/unix_events.py b/Lib/asyncio/unix_events.py
index 0f67b4d..7fc75cd 100644
--- a/Lib/asyncio/unix_events.py
+++ b/Lib/asyncio/unix_events.py
@@ -1403,6 +1403,17 @@ class ThreadedChildWatcher(AbstractChildWatcher):
 
         self._threads.pop(expected_pid)
 
+def can_use_pidfd():
+    if not hasattr(os, 'pidfd_open'):
+        return False
+    try:
+        pid = os.getpid()
+        os.close(os.pidfd_open(pid, 0))
+    except OSError:
+        # blocked by security policy like SECCOMP
+        return False
+    return True
+
 
 class _UnixDefaultEventLoopPolicy(events.BaseDefaultEventLoopPolicy):
     """UNIX event loop policy with a watcher for child processes."""
@@ -1415,7 +1426,10 @@ class _UnixDefaultEventLoopPolicy(events.BaseDefaultEventLoopPolicy):
     def _init_watcher(self):
         with events._lock:
             if self._watcher is None:  # pragma: no branch
-                self._watcher = ThreadedChildWatcher()
+                if can_use_pidfd():
+                    self._watcher = PidfdChildWatcher()
+                else:
+                    self._watcher = ThreadedChildWatcher()
                 if threading.current_thread() is threading.main_thread():
                     self._watcher.attach_loop(self._local._loop)