linux-kernel - Re: [PATCH next v3] sbitmap: fix lockup while swapping

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Message-ID: <YzX4brqWfvoa/ErM@kbusch-mbp.dhcp.thefacebook.com>
Date:   Thu, 29 Sep 2022 13:56:30 -0600
From:   Keith Busch <kbusch@...nel.org>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
        Yu Kuai <yukuai1@...weicloud.com>,
        Liu Song <liusong@...ux.alibaba.com>,
        Hillf Danton <hdanton@...a.com>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH next v3] sbitmap: fix lockup while swapping

On Thu, Sep 29, 2022 at 12:50:12PM -0700, Hugh Dickins wrote:
> @@ -587,7 +587,7 @@ static struct sbq_wait_state *sbq_wake_p
>  	for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
>  		struct sbq_wait_state *ws = &sbq->ws[wake_index];
>  
> -		if (waitqueue_active(&ws->wait)) {
> +		if (waitqueue_active(&ws->wait) && atomic_read(&ws->wait_cnt)) {
>  			if (wake_index != atomic_read(&sbq->wake_index))
>  				atomic_set(&sbq->wake_index, wake_index);
>  			return ws;

This change makes sense and looks good. Thanks for the follow up.

Reviewed-by: Keith Busch <kbusch@...nel.org>