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Bug report
Bug description:
Here is a simple repro:
import asyncio
import os
async def main():
pid = os.fork()
if pid:
os.waitpid(pid, 0)
asyncio.run(main())The traceback looks like:
Traceback (most recent call last):
File "/usr/local/Cellar/python@3.11/3.11.10/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/runners.py", line 190, in run
return runner.run(main)
^^^^^^^^^^^^^^^^
File "/usr/local/Cellar/python@3.11/3.11.10/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/runners.py", line 118, in run
return self._loop.run_until_complete(task)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/Cellar/python@3.11/3.11.10/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/base_events.py", line 641, in run_until_complete
self.run_forever()
File "/usr/local/Cellar/python@3.11/3.11.10/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/base_events.py", line 608, in run_forever
self._run_once()
File "/usr/local/Cellar/python@3.11/3.11.10/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/base_events.py", line 1898, in _run_once
event_list = self._selector.select(timeout)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/Cellar/python@3.11/3.11.10/Frameworks/Python.framework/Versions/3.11/lib/python3.11/selectors.py", line 566, in select
kev_list = self._selector.control(None, max_ev, timeout)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
OSError: [Errno 9] Bad file descriptor
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "~/forkasyncio.py", line 9, in <module>
asyncio.run(main())
File "/usr/local/Cellar/python@3.11/3.11.10/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/runners.py", line 189, in run
with Runner(debug=debug) as runner:
File "/usr/local/Cellar/python@3.11/3.11.10/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/runners.py", line 63, in __exit__
self.close()
File "/usr/local/Cellar/python@3.11/3.11.10/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/runners.py", line 72, in close
loop.run_until_complete(loop.shutdown_asyncgens())
File "/usr/local/Cellar/python@3.11/3.11.10/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/base_events.py", line 641, in run_until_complete
self.run_forever()
File "/usr/local/Cellar/python@3.11/3.11.10/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/base_events.py", line 608, in run_forever
self._run_once()
File "/usr/local/Cellar/python@3.11/3.11.10/Frameworks/Python.framework/Versions/3.11/lib/python3.11/asyncio/base_events.py", line 1898, in _run_once
event_list = self._selector.select(timeout)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/Cellar/python@3.11/3.11.10/Frameworks/Python.framework/Versions/3.11/lib/python3.11/selectors.py", line 566, in select
kev_list = self._selector.control(None, max_ev, timeout)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
OSError: [Errno 9] Bad file descriptor
sys:1: RuntimeWarning: coroutine 'BaseEventLoop.shutdown_asyncgens' was never awaited
I believe the traceback is produced by the child process.
I would not expect bad file descriptor in either the parent or the child because fork is supposed to copy the open file descriptors. I have even tried a custom fork module to ensure os.fork isn't closing the file descriptor.
The issue also happens if the child does sys.exit(). I find the best workaround is to have the child do os._exit(0):
import asyncio
import os
import sys
async def main():
pid = os.fork()
if pid:
os.waitpid(pid, 0)
else:
sys.stdout.flush()
sys.stderr.flush()
os._exit(0)
asyncio.run(main())This produces no traceback. I also avoid doing anything asyncio in the child.
I'm mainly curious about what file descriptor is bad; it doesn't seem possible.
It sounds like this issue could be fixed by #99539, but I still reproduce the issue in 3.12.7 and 3.13.0, though with a slightly different exception:
Traceback (most recent call last):
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/runners.py", line 194, in run
return runner.run(main)
^^^^^^^^^^^^^^^^
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/runners.py", line 118, in run
return self._loop.run_until_complete(task)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/base_events.py", line 674, in run_until_complete
self.run_forever()
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/base_events.py", line 641, in run_forever
self._run_once()
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/base_events.py", line 1948, in _run_once
event_list = self._selector.select(timeout)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/selectors.py", line 566, in select
kev_list = self._selector.control(None, max_ev, timeout)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: I/O operation on closed kqueue object
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/runners.py", line 71, in close
loop.run_until_complete(loop.shutdown_asyncgens())
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/base_events.py", line 674, in run_until_complete
self.run_forever()
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/base_events.py", line 641, in run_forever
self._run_once()
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/base_events.py", line 1948, in _run_once
event_list = self._selector.select(timeout)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/selectors.py", line 566, in select
kev_list = self._selector.control(None, max_ev, timeout)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: I/O operation on closed kqueue object
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "~/forkasyncio.py", line 10, in <module>
asyncio.run(main())
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/runners.py", line 193, in run
with Runner(debug=debug, loop_factory=loop_factory) as runner:
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/runners.py", line 62, in __exit__
self.close()
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/runners.py", line 77, in close
loop.close()
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/unix_events.py", line 68, in close
super().close()
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/selector_events.py", line 104, in close
self._close_self_pipe()
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/selector_events.py", line 111, in _close_self_pipe
self._remove_reader(self._ssock.fileno())
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/selector_events.py", line 305, in _remove_reader
self._selector.unregister(fd)
File "/Users/will/.pyenv/versions/3.12.7/lib/python3.12/selectors.py", line 542, in unregister
self._selector.control([kev], 0, 0)
ValueError: I/O operation on closed kqueue object
/Users/will/.pyenv/versions/3.12.7/lib/python3.12/asyncio/base_events.py:712: RuntimeWarning: coroutine 'BaseEventLoop.shutdown_asyncgens' was never awaited
CPython versions tested on:
3.11
Operating systems tested on:
macOS
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Python modules in the Lib dirPython modules in the Lib dirAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error
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