From: Eli Zaretskii <eliz@gnu.org>
To: Andreas Schwab <schwab@linux-m68k.org>
Cc: phst@google.com, p.stephani2@gmail.com, emacs-devel@gnu.org
Subject: Re: scratch/sigchld-fd 8f0ce42 1/2: Fix deadlock when receiving SIGCHLD during 'pselect'.
Date: Wed, 20 Jan 2021 05:37:41 +0200 [thread overview]
Message-ID: <83r1mg6zy2.fsf@gnu.org> (raw)
In-Reply-To: <871regr6x5.fsf@igel.home> (message from Andreas Schwab on Tue, 19 Jan 2021 21:46:46 +0100)
> From: Andreas Schwab <schwab@linux-m68k.org>
> Cc: Philipp Stephani <p.stephani2@gmail.com>, phst@google.com,
> emacs-devel@gnu.org
> Date: Tue, 19 Jan 2021 21:46:46 +0100
>
> On Jan 19 2021, Eli Zaretskii wrote:
>
> > I'd be happier if we had some direct evidence to these effects. I'd
> > also be surprised to hear that pselect doesn't return with EINTR when
> > SIGCHLD comes in. It is more likely that SIGCHLD is delivered before
> > we call pselect, but if that is the case, we should be able to
> > reliably detect that, I think.
>
> If you want reliable detection of SIGCHLD, you need to block the signal
> around pselect and let pselect unblock it, atomically.
AFAIU, this is an issue for programs that install a SIGCHLD handler
immediately before calling pselect. But Emacs has a SIGCHLD handler
installed at all times, so if the signal hits outside of the pselect
call, we should be able to detect that reliably.
next prev parent reply other threads:[~2021-01-20 3:37 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210116184947.2105.45267@vcs0.savannah.gnu.org>
[not found] ` <20210116184949.3C17C211A5@vcs0.savannah.gnu.org>
2021-01-19 15:10 ` scratch/sigchld-fd 8f0ce42 1/2: Fix deadlock when receiving SIGCHLD during 'pselect' Eli Zaretskii
2021-01-19 18:21 ` Philipp Stephani
2021-01-19 19:14 ` Eli Zaretskii
2021-01-19 20:22 ` Philipp Stephani
2021-01-20 15:05 ` Eli Zaretskii
2021-01-23 17:36 ` Philipp Stephani
2021-01-23 18:23 ` Eli Zaretskii
2021-01-23 18:30 ` Philipp Stephani
2021-01-19 20:46 ` Andreas Schwab
2021-01-19 20:58 ` Philipp Stephani
2021-01-20 18:07 ` Andreas Schwab
2021-01-20 3:37 ` Eli Zaretskii [this message]
2021-01-20 8:37 ` Andreas Schwab
2021-01-20 8:52 ` Eli Zaretskii
2021-01-20 9:18 ` Andreas Schwab
2021-01-20 10:14 ` Eli Zaretskii
2021-01-20 10:17 ` Andreas Schwab
2021-01-20 15:30 ` Eli Zaretskii
2021-01-20 15:48 ` Andreas Schwab
2021-01-20 16:40 ` Eli Zaretskii
2021-01-20 16:44 ` Andreas Schwab
2021-01-20 17:03 ` Eli Zaretskii
2021-01-20 17:30 ` Andreas Schwab
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