[debbugs-tracker] bug#27553: closed ([PATCH shepherd] Register SIGCHLD handler after primitive fork)

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Your message dated Thu, 07 Sep 2017 16:49:36 +0200
with message-id <address@hidden>
and subject line Re: [bug#27553] [PATCH shepherd] Register SIGCHLD handler 
after primitive fork
has caused the debbugs.gnu.org bug report #27553,
regarding [PATCH shepherd] Register SIGCHLD handler after primitive fork
to be marked as done.

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27553: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=27553
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--- Begin Message --- Subject: [PATCH shepherd] Register SIGCHLD handler after primitive fork Date: Sun, 2 Jul 2017 03:11:01 +0200

Hi all,

I am not sure if this is also the proper ML for the GNU Shepherd, but looking in the archives lead me to believe it actually is. If not, I suggest the gnu.org page for shepherd be updated with the correct info.

I recently starting playing around with user shepherd, and found out that when running a shepherd 0.3.2 daemonized as non-init process (via "(action 'shepherd 'daemonize)"), zombie processes are created whenever you start and subsequently stop any service.

Thinking I did something wrong, I asked lfam on #guix to share his (very helpful) init.scm for user shepherd, yet I still noticed the same behaviour.

I believe commit `efa2f45c5f7dc735407381b7b8a83d6c37f828db' inadvertently introduced an ordering issue, where the SIGCHLD handler is registered /before/ shepherd has the chance to daemonize. I believe the following trivial patch addresses this snafu.

Regards,

Jelle

0001-Register-SIGCHLD-handler-after-primitive-fork.patch
Description: Text Data

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> --- Begin Message ---
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> Subject: 
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> Re: [bug#27553] [PATCH shepherd] Register SIGCHLD handler after primitive fork
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> Date: 
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> Thu, 07 Sep 2017 16:49:36 +0200
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> User-agent: 
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> Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux)
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> Heya!
>
> Jelle Licht <address@hidden> skribis:
>
> > I just tested what Ludo' proposed, and it seems to work like a charm.
> > Seeing as we might be seeing more non-init shepherd instances w.r.t.
> >  user services and the possible service extension to `guix environment',
> > I think it would be a good call to fix this bug :-).
>
> Indeed, thanks for the reminder.
>
> > From db942182224dfc0accad94897dd2122b128eef07 Mon Sep 17 00:00:00 2001
> > From: Jelle Licht <address@hidden>
> > Date: Thu, 7 Sep 2017 00:52:49 +0200
> > Subject: [PATCH] Lazily register SIGCHLD hander on first call to
> >  'fork+exec-command'.
> >
> > * modules/shepherd.scm (main): Move unconditional top-level call to 
> > 'sigaction' to...
> > * modules/shepherd/service.scm (fork+exec-command): here. Use new variable.
> > (%sigchld-handler-installed?): New variable.
>
> LGTM, applied!
>
> Ludo’.
>
>
> --- End Message ---