From: Bart Van Assche <bvanassche@acm.org>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
Hannes Reinecke <hare@suse.com>,
Greg KH <gregkh@linuxfoundation.org>,
Mike Snitzer <snitzer@redhat.com>
Subject: Re: [PATCH V2 6/6] block: split .sysfs_lock into two locks
Date: Fri, 23 Aug 2019 09:36:20 -0700 [thread overview]
Message-ID: <eaeec312-a8d0-09c7-2e05-2804a04433f3@acm.org> (raw)
In-Reply-To: <20190823010804.GA16810@ming.t460p>
On 8/22/19 6:08 PM, Ming Lei wrote:
> On Thu, Aug 22, 2019 at 12:52:54PM -0700, Bart Van Assche wrote:
>> Shouldn't blk_register_queue() and blk_unregister_queue() be serialized
>> against blk_mq_update_nr_hw_queues()? Allowing these calls to proceed
>
> It can be easy to say than done. We depends on users for sync
> between blk_register_queue() and blk_unregister_queue(), also
> there are several locks involved in blk_mq_update_nr_hw_queues().
>
> Now, the sync is done via .sysfs_lock, and so far not see issues in this
> area. This patch just converts the .sysfs_lock into .sysfs_dir_lock for
> same purpose.
>
> If you have simple and workable patch to serialize blk_register_queue() and
> blk_unregister_queue() against blk_mq_update_nr_hw_queues(), I am happy to
> review. Otherwise please consider to do it in future, and it shouldn't a
> blocker for fixing this deadlock, should it?
Since what I requested would result in serialization across request
queues of I/O scheduler changes, let's keep this for a later time.
Bart.
next prev parent reply other threads:[~2019-08-23 16:36 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-21 9:15 [PATCH V2 0/6] block: don't acquire .sysfs_lock before removing mq & iosched kobjects Ming Lei
2019-08-21 9:15 ` [PATCH V2 1/6] block: Remove blk_mq_register_dev() Ming Lei
2019-08-21 9:15 ` [PATCH V2 2/6] block: don't hold q->sysfs_lock in elevator_init_mq Ming Lei
2019-08-21 15:51 ` Bart Van Assche
2019-08-21 9:15 ` [PATCH V2 3/6] blk-mq: don't hold q->sysfs_lock in blk_mq_map_swqueue Ming Lei
2019-08-21 15:53 ` Bart Van Assche
2019-08-26 2:11 ` Ming Lei
2019-08-21 9:15 ` [PATCH V2 4/6] blk-mq: don't hold q->sysfs_lock in blk_mq_realloc_hw_ctxs() Ming Lei
2019-08-21 15:56 ` Bart Van Assche
2019-08-26 2:25 ` Ming Lei
2019-08-21 9:15 ` [PATCH V2 5/6] block: add helper for checking if queue is registered Ming Lei
2019-08-21 15:57 ` Bart Van Assche
2019-08-21 9:15 ` [PATCH V2 6/6] block: split .sysfs_lock into two locks Ming Lei
2019-08-21 16:18 ` Bart Van Assche
2019-08-22 1:28 ` Ming Lei
2019-08-22 19:52 ` Bart Van Assche
2019-08-23 1:08 ` Ming Lei
2019-08-23 16:36 ` Bart Van Assche [this message]
2019-08-23 16:46 ` Bart Van Assche
2019-08-23 22:49 ` Ming Lei
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