Re: [RFC PATCH] blk-mq: fixup RESTART when queue becomes idle

[Jens Axboe]

On 1/19/18 8:20 AM, Bart Van Assche wrote:
> On Fri, 2018-01-19 at 15:26 +0800, Ming Lei wrote:
>> Please see queue_delayed_work_on(), hctx->run_work is shared by all
>> scheduling, once blk_mq_delay_run_hw_queue(100ms) returns, no new
>> scheduling can make progress during the 100ms.
> 
> How about addressing that as follows:
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index f7515dd95a36..57f8379a476d 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1403,9 +1403,9 @@ static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async,
>  		put_cpu();
>  	}
>  
> -	kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
> -					 &hctx->run_work,
> -					 msecs_to_jiffies(msecs));
> +	kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
> +				    &hctx->run_work,
> +				    msecs_to_jiffies(msecs));
>  }

Exactly. That's why I said it was just a bug in my previous email, not
honoring a newer run is just stupid. Only other thing you have to be
careful with here is the STOPPED bit.

-- 
Jens Axboe