linux-kernel - Re: [PATCH -next v2] blk-mq: fix potential io hang by wrong 'wake

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Date:   Mon, 12 Jun 2023 09:56:26 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     jack@...e.cz, qiulaibin@...wei.com,
        andriy.shevchenko@...ux.intel.com,
        Yu Kuai <yukuai1@...weicloud.com>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH -next v2] blk-mq: fix potential io hang by wrong
 'wake_batch'


On Sat, 10 Jun 2023 10:30:43 +0800, Yu Kuai wrote:
> In __blk_mq_tag_busy/idle(), updating 'active_queues' and calculating
> 'wake_batch' is not atomic:
> 
> t1:			t2:
> _blk_mq_tag_busy	blk_mq_tag_busy
> inc active_queues
> // assume 1->2
> 			inc active_queues
> 			// 2 -> 3
> 			blk_mq_update_wake_batch
> 			// calculate based on 3
> blk_mq_update_wake_batch
> /* calculate based on 2, while active_queues is actually 3. */
> 
> [...]

Applied, thanks!

[1/1] blk-mq: fix potential io hang by wrong 'wake_batch'
      commit: 4f1731df60f9033669f024d06ae26a6301260b55

Best regards,
-- 
Jens Axboe