Date: Thu, 4 Dec 2025 10:03:22 -0600
From: Nathan Bossart <nathandbossart@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: pgsql: Add pg_atomic_unlocked_write_u64
Message-ID: <aTGwysvF2lDmK2lP@nathan>
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On Thu, Dec 04, 2025 at 10:56:12AM -0500, Andres Freund wrote:
> The whole point of the _unlocked_ function is to use it for modifying an
> atomic that doesn't need to actually be atomic when modified by that
> function. The current use-case for it is to to modify BufferDesc->state for
> temporary table buffers. Those obviously can't be shared across processes and
> therefore don't need an atomic operation to be modified. In the referenced
> thread I'm working on converting BufferDesc->state to be a 64bit atomic, hence
> the need for pg_atomic_unlocked_write_u64().
> 
> I didn't notice that the comment for pg_atomic_unlocked_write_u32() makes that
> claim about partial writes not being visible. I think we should just remove
> that claim.

+1 to updating the comment with this context.

-- 
nathan