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
Date: Thu, 4 Dec 2025 09:51:10 -0600
Message-ID: <aTGt7q4Jvn97uGAx@nathan> (raw)
In-Reply-To: <E1vQwSk-002fZh-2h@gemulon.postgresql.org>
References: <E1vQwSk-002fZh-2h@gemulon.postgresql.org>
On Wed, Dec 03, 2025 at 11:40:47PM +0000, Andres Freund wrote:
> Add pg_atomic_unlocked_write_u64
>
> The 64bit equivalent of pg_atomic_unlocked_write_u32(), to be used in an
> upcoming patch converting BufferDesc.state into a 64bit atomic.
I noticed that this new function was defined as
ptr->value = val;
and couldn't figure out why that was safe. Above
pg_atomic_unlocked_write_u32(), I see this comment:
* The write is guaranteed to succeed as a whole, i.e. it's not possible to
* observe a partial write for any reader. ...
But the new 64-bit version doesn't seem to be surrounded by a check for
PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY, and I found no discussion about it in
the commit message or the linked thread. Am I missing something here?
--
nathan
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To: pgsql-committers@postgresql.org
Cc: nathandbossart@gmail.com, andres@anarazel.de, pgsql-hackers@lists.postgresql.org
Subject: Re: pgsql: Add pg_atomic_unlocked_write_u64
In-Reply-To: <aTGt7q4Jvn97uGAx@nathan>
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