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From: Bart Schaefer <schaefer@brasslantern.com>
To: Jun T <takimoto-j@kba.biglobe.ne.jp>
Cc: Zsh hackers list <zsh-workers@zsh.org>
Subject: Re: zargs with -P intermittently failing in zsh 5.9 and macOS
Date: Fri, 27 May 2022 09:10:29 -0700	[thread overview]
Message-ID: <CAH+w=7apQ0aN-xUsyAftJZORJ0iRkpO4Q5ZoOOrMcdeJGH_3Qw@mail.gmail.com> (raw)
In-Reply-To: <8CB92976-5B21-4239-844E-93C88EC734F5@kba.biglobe.ne.jp>

On Thu, May 26, 2022 at 10:30 PM Jun T <takimoto-j@kba.biglobe.ne.jp> wrote:
> When wait_for_processes() is called (in signal handler?), wait3(&state)
> _sometimes_ returns with WIFCONTINUED(status) set to true.
> Then wait_for_processes() calls addbgstatus(pid, val) with
> val=WEXITSTATUS(status)=19.
> Later the process exits normally, and addbgstatus(pid, 0) is called.
> This means bgstatus_list has two entries for the pid.
> When 'wait pid' calls getbgstatus(pid), it finds the entry with status=19
> and returns it.

Even if it's correct to have two entries, it's wrong to return the
least recent one.

> A simple fix would be, at line 584 of signals.c,
> (A) call addbgstatus() only if WIFCONTINUED() is not true.

I think that's insufficient ... we should be recording the most recent
state, per your question about WIFSTOPPED.

> So I guess we need to call addbgstatus() only if the process has actually
> exited (or killed). If this is the case, better solution would be
> (B) call addbgstatus() only if WIFEXITED() or WIFSIGNALED() is true.
> This it the patch below.

Does that really work?  I would expect WIFSIGNALED to be true when
each of WIFSTOPPED and WIFCONTINUED is also true, so it wouldn't
change anything?  (There isn't any way to stop/continue without using
a signal that I can think of.)

> Or, if we want to call addbgstatus() unconditionally,
> (C) modify addbgstatus() so that if there is already an entry for
> the pid then update it instead of adding a new entry.

I think either that, or

(D) Make sure getbgstatus() always returns the most recent entry.

But ... there isn't any way for a user / script to examine more than
one job status per PID, so unless we're using it internally somewhere
(?) I would think (C) is best.

  reply	other threads:[~2022-05-27 16:11 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-24 16:09 Eric Nielsen
2022-05-24 17:32 ` Bart Schaefer
2022-05-24 20:21   ` Eric Nielsen
2022-05-24 20:35     ` Bart Schaefer
2022-05-26  8:57   ` Jun T
2022-05-26 11:21     ` Jun. T
2022-05-27  3:39     ` Bart Schaefer
2022-05-27  4:18       ` Lawrence Velázquez
2022-05-27  5:29       ` Jun T
2022-05-27 16:10         ` Bart Schaefer [this message]
2022-05-27 17:25           ` Jun. T
2022-05-29  3:30             ` Bart Schaefer
2022-05-29 14:47               ` Jun. T
2022-05-29 20:07                 ` Bart Schaefer
2022-05-30 11:16                   ` Jun T
2022-06-07  6:51                     ` Jun T
2022-06-09  2:56                       ` Bart Schaefer
2022-06-12 16:43                 ` Eric Nielsen

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