From: Bart Van Assche <bvanassche@acm.org>
To: Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>
Cc: 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 4/6] blk-mq: don't hold q->sysfs_lock in blk_mq_realloc_hw_ctxs()
Date: Wed, 21 Aug 2019 08:56:36 -0700 [thread overview]
Message-ID: <51cf9611-c62f-3dcf-2447-d8bde28bc238@acm.org> (raw)
In-Reply-To: <20190821091506.21196-5-ming.lei@redhat.com>
On 8/21/19 2:15 AM, Ming Lei wrote:
> blk_mq_realloc_hw_ctxs() is called from blk_mq_init_allocated_queue()
> and blk_mq_update_nr_hw_queues(). For the former caller, the kobject
> isn't exposed to userspace yet. For the latter caller, sysfs/debugfs
> is un-registered before updating nr_hw_queues.
>
> On the other hand, commit 2f8f1336a48b ("blk-mq: always free hctx after
> request queue is freed") moves freeing hctx into queue's release
> handler, so there won't be race with queue release path too.
>
> So don't hold q->sysfs_lock in blk_mq_realloc_hw_ctxs().
How about mentioning that the locking at the start of
blk_mq_update_nr_hw_queues() serializes all blk_mq_realloc_hw_ctxs()
calls that happen after a queue has been registered in sysfs?
Anyway:
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
next prev parent reply other threads:[~2019-08-21 15:56 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 [this message]
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
2019-08-23 16:46 ` Bart Van Assche
2019-08-23 22:49 ` Ming Lei
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=51cf9611-c62f-3dcf-2447-d8bde28bc238@acm.org \
--to=bvanassche@acm.org \
--cc=axboe@kernel.dk \
--cc=gregkh@linuxfoundation.org \
--cc=hare@suse.com \
--cc=hch@infradead.org \
--cc=linux-block@vger.kernel.org \
--cc=ming.lei@redhat.com \
--cc=snitzer@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox