From: Christoph Hellwig <hch@infradead.org>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, Alasdair Kergon <agk@redhat.com>,
Mike Snitzer <snitzer@kernel.org>,
linux-block@vger.kernel.org, dm-devel@lists.linux.dev
Subject: Re: [PATC] block: update queue limits atomically
Date: Wed, 19 Mar 2025 22:25:35 -0700 [thread overview]
Message-ID: <Z9umz8lVGwvuc3ZG@infradead.org> (raw)
In-Reply-To: <ee66a4f2-ecc4-68d2-4594-a0bcba7ffe9c@redhat.com>
On Tue, Mar 18, 2025 at 03:26:10PM +0100, Mikulas Patocka wrote:
> The block limits may be read while they are being modified. The statement
> "q->limits = *lim" is not really atomic. The compiler may turn it into
> memcpy (clang does).
And that is intentional.
> This commit changes it to use WRITE_ONCE, so that individual words are
> updated atomically.
You fail to explain why the intentended non-atomic semantics are a
problem.
Note: it usually helps to Cc the other of the commit you suspect is
broken if you want a quick resolution.
prev parent reply other threads:[~2025-03-20 5:25 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-18 14:26 [PATC] block: update queue limits atomically Mikulas Patocka
2025-03-18 14:56 ` Ming Lei
2025-03-18 15:31 ` Mikulas Patocka
2025-03-19 1:22 ` Ming Lei
2025-03-19 1:58 ` Jens Axboe
2025-03-19 21:18 ` Mikulas Patocka
2025-03-20 2:22 ` Ming Lei
2025-03-20 12:58 ` Jens Axboe
2025-03-20 5:26 ` Christoph Hellwig
2025-03-18 15:58 ` Bart Van Assche
2025-03-18 16:13 ` Mikulas Patocka
2025-03-20 5:25 ` Christoph Hellwig [this message]
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