From: Ming Lei <ming.lei@redhat.com>
To: James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: Jens Axboe <axboe@kernel.dk>, Yi Zhang <yi.zhang@redhat.com>,
linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
"Martin K . Petersen" <martin.petersen@oracle.com>,
linux-scsi@vger.kernel.org, ming.lei@redhat.com
Subject: Re: [PATCH 3/4] scsi: make sure that request queue queiesce and unquiesce balanced
Date: Tue, 9 Nov 2021 08:44:06 +0800 [thread overview]
Message-ID: <YYnEVuwp/jMngPYo@T590> (raw)
In-Reply-To: <08f0e186093b0d5067347a1376228010cb4cc7f4.camel@HansenPartnership.com>
Hello James,
On Mon, Nov 08, 2021 at 11:42:01AM -0500, James Bottomley wrote:
> On Wed, 2021-11-03 at 11:43 +0800, Ming Lei wrote:
> [...]
> > +void scsi_start_queue(struct scsi_device *sdev)
> > +{
> > + if (cmpxchg(&sdev->queue_stopped, 1, 0))
> > + blk_mq_unquiesce_queue(sdev->request_queue);
> > +}
> > +
> > +static void scsi_stop_queue(struct scsi_device *sdev, bool nowait)
> > +{
> > + if (!cmpxchg(&sdev->queue_stopped, 0, 1)) {
> > + if (nowait)
> > + blk_mq_quiesce_queue_nowait(sdev-
> > >request_queue);
> > + else
> > + blk_mq_quiesce_queue(sdev->request_queue);
> > + } else {
> > + if (!nowait)
> > + blk_mq_wait_quiesce_done(sdev->request_queue);
> > + }
> > +}
>
> This looks counter intuitive. I assume it's done so that if we call
> scsi_stop_queue when the queue has already been stopped, it waits until
The motivation is to balance blk_mq_quiesce_queue_nowait()/blk_mq_quiesce_queue()
and blk_mq_unquiesce_queue().
That needs one extra mutex to cover the quiesce action and update
the flag, but we can't hold the mutex in scsi_internal_device_block_nowait(),
so take this way with the atomic flag.
> the queue is actually quiesced before returning so the behaviour is the
> same in the !nowait case? Some sort of comment explaining that would
> be useful.
I will add comment on the current usage.
Thanks,
Ming
next prev parent reply other threads:[~2021-11-09 0:44 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-03 3:43 [PATCH 0/4] block: fix concurrent quiesce Ming Lei
2021-11-03 3:43 ` [PATCH 1/4] blk-mq: add one API for waiting until quiesce is done Ming Lei
2021-11-03 3:43 ` [PATCH 2/4] scsi: avoid to quiesce sdev->request_queue two times Ming Lei
2021-11-03 3:43 ` [PATCH 3/4] scsi: make sure that request queue queiesce and unquiesce balanced Ming Lei
2021-11-08 16:42 ` James Bottomley
2021-11-09 0:44 ` Ming Lei [this message]
2021-11-09 3:18 ` Ming Lei
2021-11-09 3:22 ` James Bottomley
2021-11-03 3:43 ` [PATCH 4/4] nvme: wait until quiesce is done Ming Lei
2021-11-08 16:45 ` Keith Busch
2021-11-12 15:38 ` Sagi Grimberg
2021-11-07 21:20 ` [PATCH 0/4] block: fix concurrent quiesce Jens Axboe
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=YYnEVuwp/jMngPYo@T590 \
--to=ming.lei@redhat.com \
--cc=James.Bottomley@hansenpartnership.com \
--cc=axboe@kernel.dk \
--cc=linux-block@vger.kernel.org \
--cc=linux-nvme@lists.infradead.org \
--cc=linux-scsi@vger.kernel.org \
--cc=martin.petersen@oracle.com \
--cc=yi.zhang@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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.