From: | Noah Misch <noah(at)leadboat(dot)com> |
---|---|
To: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com> |
Cc: | Andres Freund <andres(at)anarazel(dot)de>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Nathan Bossart <nathandbossart(at)gmail(dot)com>, Melanie Plageman <melanieplageman(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: race condition when writing pg_control |
Date: | 2024-07-12 11:43:22 |
Message-ID: | 20240712114322.08.nmisch@google.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Sat, May 18, 2024 at 05:29:12PM +1200, Thomas Munro wrote:
> On Fri, May 17, 2024 at 4:46 PM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> > The specific problem here is that LocalProcessControlFile() runs in
> > every launched child for EXEC_BACKEND builds. Windows uses
> > EXEC_BACKEND, and Windows' NTFS file system is one of the two file
> > systems known to this list to have the concurrent read/write data
> > mashing problem (the other being ext4).
> First idea idea I've come up with to avoid all of that: pass a copy of
> the "proto-controlfile", to coin a term for the one read early in
> postmaster startup by LocalProcessControlFile(). As far as I know,
> the only reason we need it is to suck some settings out of it that
> don't change while a cluster is running (mostly can't change after
> initdb, and checksums can only be {en,dis}abled while down). Right?
> Children can just "import" that sucker instead of calling
> LocalProcessControlFile() to figure out the size of WAL segments yada
> yada, I think? Later they will attach to the real one in shared
> memory for all future purposes, once normal interlocking is allowed.
I like that strategy, particularly because it recreates what !EXEC_BACKEND
backends inherit from the postmaster. It might prevent future bugs that would
have been specific to EXEC_BACKEND.
> I dunno. Draft patch attached. Better plans welcome. This passes CI
> on Linux systems afflicted by EXEC_BACKEND, and Windows. Thoughts?
Looks reasonable. I didn't check over every detail, given the draft status.
From | Date | Subject | |
---|---|---|---|
Next Message | Bertrand Drouvot | 2024-07-12 12:10:26 | Re: Flush pgstats file during checkpoints |
Previous Message | Alexander Pyhalov | 2024-07-12 11:39:13 | Partition-wise join with whole row vars |