linux-kernel - Re: [PATCH] block: remove redundant explicit memory barrier from rq

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Message-Id: <7C429559-E91C-4732-901B-0D49C2D083F7@linux.dev>
Date: Tue, 22 Oct 2024 14:31:53 +0800
From: Muchun Song <muchun.song@...ux.dev>
To: Jens Axboe <axboe@...nel.dk>
Cc: Muchun Song <songmuchun@...edance.com>,
 josef@...icpanda.com,
 oleg@...hat.com,
 linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Omar Sandoval <osandov@...ndov.com>
Subject: Re: [PATCH] block: remove redundant explicit memory barrier from
 rq_qos waiter and waker



> On Oct 21, 2024, at 21:45, Jens Axboe <axboe@...nel.dk> wrote:
> 
> On 10/21/24 2:52 AM, Muchun Song wrote:
>> The memory barriers in list_del_init_careful() and list_empty_careful()
>> in pairs already handle the proper ordering between data.got_token
>> and data.wq.entry. So remove the redundant explicit barriers. And also
>> change a "break" statement to "return" to avoid redundant calling of
>> finish_wait().
> 
> Not sure why you didn't CC Omar on this one, as he literally just last
> week fixed an issue related to this.

Hi Jens,

Yes. I only CC the author of patch of adding the barriers, I thought
they should be more confident about this. Thanks for your reminder.
I saw Omar's great fix. And thanks for you help me CC Omar. I think
he'll be also suitable for commenting on this patch.

Muchun,
Thanks.