Bug 672540 – sys-apps/portage: AsyncioEventLoop exception handler does not allow exit with Ctrl-C, SIGKILL required

• Status: RESOLVED FIXED
• Product: Portage Development

[Description Zac Medico 2018-12-05 01:25:53 UTC]

For example, when /var/tmp/portage runs out of space and bug 451158 is triggered, it stops like this and the user has to use SIGKILL to end the process:

> >>> Jobs: 1 of 22 complete, 3 running               Load avg: 15.6, 11.8, 10.4Exception in callback PipeLogger._output_handler(18)                                                                                
> handle: <Handle PipeLogger._output_handler(18)>
> Traceback (most recent call last):
>   File "/usr/lib64/python3.6/asyncio/events.py", line 145, in _run
>     self._callback(*self._args)
>   File "/usr/lib64/python3.6/site-packages/portage/util/_async/PipeLogger.py", line 124, in _output_handler                                                                                                       
>     log_file.flush()
> OSError: [Errno 28] No space left on device
> --Return--
> > /usr/lib64/python3.6/site-packages/portage/util/_eventloop/asyncio_event_loop.py(76)_internal_caller_exception_handler()->None                                                                                  
> -> pdb.set_trace()
> (Pdb)
We can enable Ctrl-C in this situation, like this:

> diff --git a/lib/portage/util/_eventloop/asyncio_event_loop.py b/lib/portage/util/_eventloop/asyncio_event_loop.py
> index ea0e03b23..50839ad26 100644
> --- a/lib/portage/util/_eventloop/asyncio_event_loop.py
> +++ b/lib/portage/util/_eventloop/asyncio_event_loop.py
> @@ -73,6 +73,7 @@ class AsyncioEventLoop(_AbstractEventLoop):
>                         # aid in diagnosis of the problem. If there's no tty, then
>                         # exit immediately.
>                         if all(s.isatty() for s in (sys.stdout, sys.stderr, sys.stdin)):
> +                               signal.signal(signal.SIGINT, signal.SIG_DFL)
>                                 pdb.set_trace()
>                         else:
>                                 # Normally emerge will wait for all coroutines to complete

[Comment 1 Zac Medico 2018-12-05 18:35:33 UTC]

Maybe Scheduler should override the AsyncioEventLoop exception handler when it overrides the SIGINT/SIGTERM handlers.

[Comment 2 Zac Medico 2019-04-15 23:29:03 UTC]

Maybe Scheduler could also use the asyncio loop.add_signal_handler API instead of using the signal module directly:

https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.loop.add_signal_handler

[Comment 3 Larry the Git Cow 2019-04-16 02:07:09 UTC]

The bug has been referenced in the following commit(s):

https://gitweb.gentoo.org/proj/portage.git/commit/?id=ee1f6ff69887dfa02d5c3a3ab3d61163fa504d15

commit ee1f6ff69887dfa02d5c3a3ab3d61163fa504d15
Author:     Zac Medico <[e-mail]>
AuthorDate: 2019-04-16 01:33:29 +0000
Commit:     Zac Medico <[e-mail]>
CommitDate: 2019-04-16 01:40:29 +0000

    AsyncioEventLoop: enable SIGINT in exception handler (bug 672540)
    
    Before the exception handler invokes the pdb shell, enable SIGINT so
    that the user can exit with Control-C (otherwise SIGKILL is needed).
    
    Bug: https://bugs.gentoo.org/672540
    Signed-off-by: Zac Medico <[e-mail]>

 lib/portage/util/_eventloop/asyncio_event_loop.py | 5 +++++
 1 file changed, 5 insertions(+)

[Comment 4 Zac Medico 2019-04-16 02:21:08 UTC]

(In reply to Zac Medico from comment #2)
> Maybe Scheduler could also use the asyncio loop.add_signal_handler API
> instead of using the signal module directly:
> 
> https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.loop.
> add_signal_handler

This wouldn't be useful in the context of this bug since event loop signal handlers are useless when the loop is suspended (same problem as Scheduler's existing signal handler which relies on the event loop to ultimately trigger exit).