From: Ming Lei <ming.lei@redhat.com>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, Greg KH <gregkh@linuxfoundation.org>,
Mike Snitzer <snitzer@redhat.com>
Subject: Re: [PATCH] block: don't acquire .sysfs_lock before removing mq & iosched kobjects
Date: Wed, 21 Aug 2019 10:45:05 +0800 [thread overview]
Message-ID: <20190821024503.GC24167@ming.t460p> (raw)
In-Reply-To: <b79a9f96-f085-1888-bd10-d6dc72aba30b@acm.org>
On Tue, Aug 20, 2019 at 02:07:43PM -0700, Bart Van Assche wrote:
> On 8/19/19 1:15 AM, Ming Lei wrote:
> > hctx->tags is tagset wide or host-wide, which is protected by set->tag_list_lock.
>
> Isn't the purpose of set->tag_list_lock to protect set->tag_list?
In theory, .tags is shared among all queues in tagset, so it should be
protected by tagset wide lock, what is why set->tag_list_lock is held
in blk_mq_update_nr_hw_queues().
However, both sysfs and debugfs read/write doesn't hold this lock because
the .tags won't be shrunk in blk_mq_update_nr_requests(), and
blk_mq_update_nr_hw_queues un-registers debugfs/sysfs before changing .tags.
thanks,
Ming
next prev parent reply other threads:[~2019-08-21 2:45 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-16 13:55 [PATCH] block: don't acquire .sysfs_lock before removing mq & iosched kobjects Ming Lei
2019-08-16 15:14 ` Bart Van Assche
2019-08-19 8:15 ` Ming Lei
2019-08-20 21:07 ` Bart Van Assche
2019-08-21 2:45 ` Ming Lei [this message]
2019-08-16 15:31 ` Bart Van Assche
2019-08-16 15:45 ` Ming Lei
2019-08-20 21:21 ` Bart Van Assche
2019-08-21 3:00 ` Ming Lei
2019-08-21 15:41 ` Bart Van Assche
2019-08-22 1:16 ` Ming Lei
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