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christgau/wsdd
#219Description
Bug report
I have some code in the qemu.qmp package that appears to work correctly in Python 3.6 (RIP~) through to Python 3.11. I've started testing against 3.12 and I'm finding that waiting on asyncio.Server.wait_closed() is creating a deadlock/hang.
Here's a minimal-ish reproducer:
#!/usr/bin/env python3
import asyncio
async def cause_problems():
accepted = asyncio.Event()
async def _incoming(reader, writer):
print("entered _incoming")
print("signaling outer context; we accepted a client")
accepted.set()
print("left _incoming")
print("starting server")
server = await asyncio.start_unix_server(
_incoming,
path="problems.sock",
backlog=1,
)
print("created server; waiting on a client")
await accepted.wait()
print("got a client")
print("closing server")
server.close()
print("issued close()")
await server.wait_closed()
print("finished waiting on server to close")
if __name__ == '__main__':
asyncio.run(cause_problems())You can test a simple connection using whatever you'd like; socat works to trigger the accept code, e.g. from the same directory that you run the above code, try:
socat UNIX-CONNECT:problems.sock stdoutHere's what happens in python 3.11.3
jsnow@scv ~> python3.11 hang.py
starting server
created server; waiting on a client
entered _incoming
signaling outer context; we accepted a client
left _incoming
got a client
closing server
issued close()
finished waiting on server to close
And here's 3.12.0a7:
jsnow@scv ~> python3.12 hang.py
starting server
created server; waiting on a client
entered _incoming
signaling outer context; we accepted a client
left _incoming
got a client
closing server
issued close()
When I issue ^C, we get this traceback:
^CTraceback (most recent call last):
File "/usr/lib64/python3.12/asyncio/runners.py", line 118, in run
return self._loop.run_until_complete(task)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib64/python3.12/asyncio/base_events.py", line 664, in run_until_complete
return future.result()
^^^^^^^^^^^^^^^
File "/home/jsnow/hang2.py", line 26, in cause_problems
await server.wait_closed()
File "/usr/lib64/python3.12/asyncio/base_events.py", line 384, in wait_closed
await waiter
asyncio.exceptions.CancelledError
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/home/jsnow/hang2.py", line 31, in <module>
asyncio.run(cause_problems())
File "/usr/lib64/python3.12/asyncio/runners.py", line 194, in run
return runner.run(main)
^^^^^^^^^^^^^^^^
File "/usr/lib64/python3.12/asyncio/runners.py", line 123, in run
raise KeyboardInterrupt()
KeyboardInterrupt
Your environment
- Python 3.12.0a7 (as packaged on Fedora 37)
Linux 6.2.12-200.fc37.x86_64 #1 SMP PREEMPT_DYNAMIC Thu Apr 20 23:38:29 UTC 2023- Tested on CPython 3.6 through 3.12 as available on Fedora 37. Works on 3.6, 3.7, 3.8, 3.9, 3.10 and 3.11 but fails on the 3.12 alpha package.
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