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Re: Adding locks statistics

Bertrand Drouvot <bertranddrouvot.pg@gmail.com>

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From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Andres Freund <andres@anarazel.de>, Jeff Davis <pgsql@j-davis.com>, Greg Sabino Mullane <htamfids@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2026-04-07T06:01:08Z
Lists: pgsql-hackers 
Hi,

On Tue, Apr 07, 2026 at 01:21:39PM +0900, Michael Paquier wrote:
> On Mon, Apr 06, 2026 at 03:34:44PM +0900, Michael Paquier wrote:
> > This one was a simple puzzle: there was a race condition between the
> > detach done by a local point and the wait/detach sequence.  As we want
> > a detach, dropping the local point is proving to work here.
> > 
> > I am going to do a few more runs to gain some more confidence.
> 
> Done a total of 5 runs (or 6 actually), and fixed it.
> 
> > Bertrand, could you confirm please?
> 
> That's of course always welcome.  I'll keep an eye on the CI and the
> buildfarm.

That looks to work, thanks! But I was wondering if this new version is not
introducing a new race: the injection point is not local anymore so it could be
that another process reach the new injection point. That said, even if this is
the case I think we're ok since s2 is using "query_until" so we could say that
"at least" s2 reached the injection point. The new version does not ensure that
"only" s2 reached the injection point but I think that's safe.

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix injection point detach timing problem in TAP test for lock stats

  2. Use single LWLock for lock statistics in pgstats

  3. Add tests for lock statistics, take two

  4. Remove isolation test lock-stats

  5. Avoid including clog.h in proc.h

  6. Don't include storage/lock.h in so many headers

  7. Add support for lock statistics in pgstats

  8. Move some code blocks in lock.c and proc.c

  9. Move declarations related to locktags from lock.h to new locktag.h