Re: Spinlock can be released twice in procsignal.c

Michael Paquier <michael@paquier.xyz>

From: Michael Paquier <michael@paquier.xyz>

To: Maxim Orlov <orlovmg@gmail.com>

Cc: Andrey Borodin <x4mmm@yandex-team.ru>, "Maksim.Melnikov" <m.melnikov@postgrespro.ru>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Heikki Linnakangas <hlinnaka@iki.fi>, Jelte Fennema-Nio <postgres@jeltef.nl>

Date: 2025-02-27T00:46:49Z

Lists: pgsql-hackers

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Fix possible double-release of spinlock in procsignal.c
- 62ec3e1f6786 18.0 landed

On Wed, Feb 26, 2025 at 12:33:16PM +0300, Maxim Orlov wrote:
> Done. Except for a new name for "logit" variable. Unfortunately, I can't
> think of anything sane. As an example I looked at sequence.c. The same name
> is used there. I will gladly change this name to whatever you want if it
> still look misleading or incomplete for you in some way or another. Just
> write the name that you think is correct.

"old_pss_pid", because this is an old pss_pid value from a previous
slot.  Keeping the value around after releasing the slot is also
useful for debugging, so rather than a boolean it is possible to use a
uint32.  The "sanity check" comment was also a bit out-of-order
because it was written just before acquiring the spinlock.

Tweaked a bit the whole, and the result looked OK so applied on HEAD.
--
Michael