linux-kernel - Re: [PATCH] xfs: Use xchg() in xlog_cil_insert_pcp

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Message-ID: <1a9a75bd-d946-40ec-8307-10fa04672300@riscstar.com>
Date: Wed, 20 Nov 2024 09:37:54 -0600
From: Alex Elder <elder@...cstar.com>
To: Uros Bizjak <ubizjak@...il.com>
Cc: linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
 Chandan Babu R <chandan.babu@...cle.com>, "Darrick J. Wong"
 <djwong@...nel.org>, Christoph Hellwig <hch@...radead.org>,
 Dave Chinner <dchinner@...hat.com>
Subject: Re: [PATCH] xfs: Use xchg() in xlog_cil_insert_pcp_aggregate()

On 11/20/24 9:36 AM, Uros Bizjak wrote:
> On Wed, Nov 20, 2024 at 4:34 PM Alex Elder <elder@...cstar.com> wrote:
>>
>> On 11/20/24 9:06 AM, Uros Bizjak wrote:
>>> try_cmpxchg() loop with constant "new" value can be substituted
>>> with just xchg() to atomically get and clear the location.
>>
>> You're right.  With a constant new value (0), there is no need
>> to loop to ensure we get a "stable" update.
>>
>> Is the READ_ONCE() is still needed?
> 
> No, xchg() guarantees atomic access on its own.
> 
> Uros.

Based on that:

Reviewed-by: Alex Elder <elder@...cstar.com>