Horton

Re: stopgap fix for signal handling during restore_command

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>, Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Fujii Masao <fujii@postgresql.org>, Postgres hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-02-24T04:33:23Z
Lists: pgsql-hackers

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On Fri, Feb 24, 2023 at 01:25:01PM +1300, Thomas Munro wrote:
> I think you should have a trailing \n when writing to stderr.

Oops.  I added that in v7.

> Here's that reproducer I speculated about (sorry I confused SIGQUIT
> and SIGTERM in my earlier email, ENOCOFFEE).  Seems to do the job, and
> I tested on a Linux box for good measure.  If you comment out the
> kill(), "check PROVE_TESTS=t/002_archiving.pl" works fine
> (demonstrating that that definition of system() works fine).  With the
> kill(), it reliably reaches 'TRAP: failed Assert("latch->owner_pid ==
> MyProcPid")' without your patch, and with your patch it avoids it.  (I
> believe glibc's system() could reach it too with the right timing, but
> I didn't try, my point being that the use of the OpenBSD system() here
> is only  because it's easier to grok and to wrangle.)

Thanks for providing the reproducer!  I am seeing the behavior that you
described on my Linux machine.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com

Commits

  1. windows: msvc: Define STDIN/OUT/ERR_FILENO.

  2. Avoid calling proc_exit() in processes forked by system().

  3. Move extra code out of the Pre/PostRestoreCommand() section.