linux-kernel - Re: [PATCH] driver: block: release the lo_work_lock before queue

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Message-ID: <CAFj5m9+77j1Y3nNkxqhCcJ5XN719723iudjKVYDsppWfy7sWfQ@mail.gmail.com>
Date: Tue, 11 Feb 2025 19:16:28 +0800
From: Ming Lei <ming.lei@...hat.com>
To: "zhaoyang.huang" <zhaoyang.huang@...soc.com>
Cc: Jens Axboe <axboe@...nel.dk>, Dan Schatzberg <schatzberg.dan@...il.com>, 
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Zhaoyang Huang <huangzhaoyang@...il.com>, steve.kang@...soc.com
Subject: Re: [PATCH] driver: block: release the lo_work_lock before queue_work

On Fri, Feb 7, 2025 at 5:20 PM zhaoyang.huang <zhaoyang.huang@...soc.com> wrote:
>
> From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
>
> queue_work could spin on wq->cpu_pwq->pool->lock which could lead to
> concurrent loop_process_work failed on lo_work_lock contention and
> increase the request latency. Remove this combination by moving the
> lock release ahead of queue_work.
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> ---
>  drivers/block/loop.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 8f6761c27c68..33e31cd95953 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -890,8 +890,8 @@ static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd)
>                 cmd_list = &lo->rootcg_cmd_list;
>         }
>         list_add_tail(&cmd->list_entry, cmd_list);
> -       queue_work(lo->workqueue, work);
>         spin_unlock_irq(&lo->lo_work_lock);
> +       queue_work(lo->workqueue, work);
>  }

Reviewed-by: Ming Lei <ming.lei@...hat.com>