[issue32661] ProactorEventLoop locks up on close call

[STINNER Victor]

STINNER Victor  added the comment:

bug.py calls loop.run_forever() but nothing calls stops the loop. If you add 
loop.stop() to handle_incoming_connection(), the script exits properly as soon 
as a client connects and sends some data.

> 3. I press Ctrl-C in the DOS window.  Nothing happens.

This issue has been fixed by bpo-23057. So I qualify this issue as a duplicate 
of bpo-23057.

--
nosy: +vstinner
resolution:  -> duplicate
stage:  -> resolved
status: open -> closed
superseder:  -> [Windows] asyncio: support signal handlers on Windows (feature 
request)

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[issue32661] ProactorEventLoop locks up on close call

[Antoine Pitrou]

Change by Antoine Pitrou :


--
versions: +Python 3.7

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[issue32661] ProactorEventLoop locks up on close call

[Roger Taylor]

New submission from Roger Taylor :

The following problem only occurs when I use ProactorEventLoop.  If I use 
'asyncio.get_event_loop()' it exits normally, rather than infinite looping in 
IOCP land.

1. I run the attached 'bug.py' script in a DOS window.  It is a slightly 
modified version of the asyncio echo server example.
2. It reaches 'loop.run_forever()' and blocks.  I can make connections here and 
use it as an echo server.  Or make no connections.
3. I press Ctrl-C in the DOS window.  Nothing happens.
4. I do a raw connection with Putty and try some input.
5. 'run_forever()' exits and the script proceeds to the 'loop.close()' call.  
Before this is invoked and the infinite loop entered, I see the script output 
''.

At this point, the script locks up and never reaches the next line.  It can be 
interrupted with another Ctrl-C, and the following stack track is seen:

Traceback (most recent call last):
  File "bug.py", line 39, in 
loop.close()
  File "C:\Program Files (x86)\Microsoft Visual 
Studio\Shared\Python36_64\lib\asyncio\proactor_events.py", line 437, in close
self._proactor.close()
  File "C:\Program Files (x86)\Microsoft Visual 
Studio\Shared\Python36_64\lib\asyncio\windows_events.py", line 745, in close
if not self._poll(1):
  File "C:\Program Files (x86)\Microsoft Visual 
Studio\Shared\Python36_64\lib\asyncio\windows_events.py", line 673, in _poll
status = _overlapped.GetQueuedCompletionStatus(self._iocp, ms)
KeyboardInterrupt

The following code in 'windows_events.py:IocpProactor.close' is looping 
infinitely.

while self._cache:
if not self._poll(1):
logger.debug('taking long time to close proactor')

Note that '_poll' does not actually return anything.

--
components: asyncio
files: bug.py
messages: 310655
nosy: asvetlov, rt121212121, yselivanov
priority: normal
severity: normal
status: open
title: ProactorEventLoop locks up on close call
type: behavior
versions: Python 3.6
Added file: https://bugs.python.org/file47408/bug.py

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