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From: "jianchao.wang" <jianchao.w.wang@oracle.com>
To: Ming Lei <ming.lei@redhat.com>, Bart Van Assche <bvanassche@acm.org>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org,
	James Smart <james.smart@broadcom.com>,
	Bart Van Assche <bart.vanassche@wdc.com>,
	linux-scsi@vger.kernel.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	Christoph Hellwig <hch@lst.de>,
	"James E . J . Bottomley" <jejb@linux.vnet.ibm.com>
Subject: Re: [PATCH 0/5] blk-mq: allow to run queue if queue refcount is held
Date: Mon, 1 Apr 2019 11:25:50 +0800	[thread overview]
Message-ID: <21b2000b-16b6-f5a6-692b-73143a49a4ec@oracle.com> (raw)
In-Reply-To: <20190401025237.GE30776@ming.t460p>

Hi Ming

On 4/1/19 10:52 AM, Ming Lei wrote:
>> percpu_ref_tryget_live() fails if a per-cpu counter is in the "dead" state.
>> percpu_ref_kill() changes the state of a per-cpu counter to the "dead"
>> state. blk_freeze_queue_start() calls percpu_ref_kill(). blk_cleanup_queue()
>> already calls blk_set_queue_dying() and that last function calls
>> blk_freeze_queue_start(). So I think that what you wrote is not correct and
>> that inserting a percpu_ref_tryget_live()/percpu_ref_put() pair in
>> blk_mq_run_hw_queues() or blk_mq_run_hw_queue() would make a difference and
>> also that moving the percpu_ref_exit() call into blk_release_queue() makes
>> sense.
> If percpu_ref_exit() is moved to blk_release_queue(), we still need to
> move freeing of hw queue's resource into blk_release_queue() like what
> the patchset is doing.
> 
> Then we don't need to get/put q_usage_counter in blk_mq_run_hw_queues() any more,
> do we?

IMO, if we could get a way to prevent any attempt to run queue, it would be
better and clearer.

Thanks
Jianchao

  reply	other threads:[~2019-04-01  3:25 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-31  3:09 [PATCH 0/5] blk-mq: allow to run queue if queue refcount is held Ming Lei
2019-03-31  3:09 ` [PATCH 1/5] blk-mq: re-organize blk_mq_exit_hctx() into two parts Ming Lei
2019-04-01  1:40   ` Dongli Zhang
2019-04-01  2:06     ` Ming Lei
2019-03-31  3:09 ` [PATCH 2/5] blk-mq: re-organize blk_mq_exit_hw_queues() " Ming Lei
2019-03-31  3:09 ` [PATCH 3/5] blk-mq: free hw queues in queue's release handler Ming Lei
2019-03-31  3:09 ` [PATCH 4/5] block: don't drain in-progress dispatch in blk_cleanup_queue() Ming Lei
2019-04-01  1:50   ` Dongli Zhang
2019-04-01  2:08     ` Ming Lei
2019-03-31  3:09 ` [PATCH 5/5] SCSI: don't grab queue usage counter before run queue Ming Lei
2019-04-01  1:53   ` Dongli Zhang
2019-03-31 15:27 ` [PATCH 0/5] blk-mq: allow to run queue if queue refcount is held Bart Van Assche
2019-04-01  2:00   ` Ming Lei
2019-04-01  2:39     ` Bart Van Assche
2019-04-01  2:44       ` jianchao.wang
2019-04-02 18:07         ` Bart Van Assche
2019-04-01  2:52       ` Ming Lei
2019-04-01  3:25         ` jianchao.wang [this message]
2019-04-01  3:28           ` Ming Lei
2019-04-01  9:19             ` jianchao.wang
2019-04-01 10:03               ` Ming Lei
2019-04-02  2:02                 ` jianchao.wang
2019-04-02  2:55                   ` Ming Lei
2019-04-02  8:07                     ` jianchao.wang
2019-04-02 11:05                       ` Ming Lei
2019-04-02 17:53                         ` Bart Van Assche
2019-04-03  3:20                           ` Ming Lei
2019-04-03  8:29                             ` Ming Lei
2019-04-03  8:43                               ` Ming Lei
2019-04-02 18:11                     ` Bart Van Assche
2019-04-03  3:24                       ` Ming Lei
2019-04-01  5:05         ` Dongli Zhang
2019-04-01  5:16           ` Ming Lei
2019-04-01  5:30             ` Dongli Zhang
2019-04-01  7:15               ` Ming Lei
2019-04-02  2:10                 ` Dongli Zhang
2019-04-02  2:20                   ` Ming Lei
2019-04-01  3:27       ` Ming Lei
2019-04-01  3:32         ` jianchao.wang

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