Re: [PATCH] blk-mq: avoid double ->queue_rq() because of early timeout

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On 10/24/22 6:55 PM, Ming Lei wrote:
> @@ -1593,10 +1598,18 @@ static void blk_mq_timeout_work(struct work_struct *work)
>  	if (!percpu_ref_tryget(&q->q_usage_counter))
>  		return;
>  
> -	blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next);
> +	/*
> +	 * Before walking tags, we must ensure any submit started before
> +	 * the current time has finished. Since the submit uses srcu or rcu,
> +	 * wait for a synchronization point to ensure all running submits
> +	 * have finished
> +	 */
> +	blk_mq_wait_quiesce_done(q);

I'm a little worried about this bit - so we'll basically do a sync RCU
every time the timeout timer runs... Depending on machine load, that
can take a long time.

-- 
Jens Axboe
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