From: ludovic.courtes@inria.fr (Ludovic Courtès)
To: Andy Wingo <wingo@pobox.com>
Cc: 14640-done@debbugs.gnu.org
Subject: bug#14640: SA_RESTART prevents execution of signal handlers
Date: Tue, 21 Jun 2016 09:48:33 +0200 [thread overview]
Message-ID: <87wpljdlta.fsf@inria.fr> (raw)
In-Reply-To: <87twgn59ou.fsf@pobox.com> (Andy Wingo's message of "Tue, 21 Jun 2016 08:37:37 +0200")
Andy Wingo <wingo@pobox.com> skribis:
> On Mon 17 Jun 2013 15:54, ludovic.courtes@inria.fr (Ludovic Courtès) writes:
>
>> When using SA_RESTART, signal handlers are never executed, as in this
>> example (checked on 2.0.9+):
>>
>> (sigaction SIGALRM
>> (lambda (signum)
>> (pk 'sig signum))
>> SA_RESTART)
>> (alarm 3)
>> (pk 'char (read-char))
>>
>> Presumably this is because the read(2) syscall is automatically
>> restarted, leaving no chance for the handler async to run.
>
> Thinking about this a bit -- since we always handle signals
> asynchronously and have no intention of handling them synchronously,
> then we just have to document this behavior. Done in e877e1b:
I think it’s problematic though. With the current design, signal
delivery is unreliable (with or without SA_RESTART; what we observe with
SA_RESTART occurs similarly if you make a syscall right after queuing,
but not running, an async.)
The more I think about it, the more I think a different approach is
needed. On GNU/Linux, signalfd(2) may be part of the solution.
Ludo’.
next prev parent reply other threads:[~2016-06-21 7:48 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-17 13:54 bug#14640: SA_RESTART prevents execution of signal handlers Ludovic Courtès
2016-06-21 6:37 ` Andy Wingo
2016-06-21 7:48 ` Ludovic Courtès [this message]
2016-06-21 7:59 ` Andy Wingo
2016-06-21 9:46 ` Ludovic Courtès
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