From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "ming.lei@redhat.com" <ming.lei@redhat.com>
Cc: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"jthumshirn@suse.de" <jthumshirn@suse.de>,
"hch@lst.de" <hch@lst.de>,
"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
"axboe@kernel.dk" <axboe@kernel.dk>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"oleksandr@natalenko.name" <oleksandr@natalenko.name>,
"hare@suse.com" <hare@suse.com>
Subject: Re: [PATCH v9 09/10] block, scsi: Make SCSI quiesce and resume work reliably
Date: Tue, 17 Oct 2017 20:08:18 +0000 [thread overview]
Message-ID: <1508270897.3457.7.camel@wdc.com> (raw)
In-Reply-To: <20171017004319.GB15996@ming.t460p>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==
WARNING: multiple messages have this Message-ID (diff)
From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "ming.lei@redhat.com" <ming.lei@redhat.com>
Cc: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"jthumshirn@suse.de" <jthumshirn@suse.de>,
"hch@lst.de" <hch@lst.de>,
"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
"axboe@kernel.dk" <axboe@kernel.dk>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"oleksandr@natalenko.name" <oleksandr@natalenko.name>,
"hare@suse.com" <hare@suse.com>
Subject: Re: [PATCH v9 09/10] block, scsi: Make SCSI quiesce and resume work reliably
Date: Tue, 17 Oct 2017 20:08:18 +0000 [thread overview]
Message-ID: <1508270897.3457.7.camel@wdc.com> (raw)
In-Reply-To: <20171017004319.GB15996@ming.t460p>
On Tue, 2017-10-17 at 08:43 +0800, Ming Lei wrote:
> On Mon, Oct 16, 2017 at 04:29:04PM -0700, Bart Van Assche wrote:
> > [ ... ]
> > int
> > scsi_device_quiesce(struct scsi_device *sdev)
> > {
> > + struct request_queue *q = sdev->request_queue;
> > int err;
> >
> > + /*
> > + * It is allowed to call scsi_device_quiesce() multiple times from
> > + * the same context but concurrent scsi_device_quiesce() calls are
> > + * not allowed.
> > + */
> > + WARN_ON_ONCE(sdev->quiesced_by && sdev->quiesced_by != current);
>
> If the above line and comment is removed, everything is still fine,
> either nested calling or concurrent calling, isn't it?
If scsi_device_quiesce() is called concurrently from two different threads
then the first scsi_device_resume() call will resume I/O for *both* contexts.
That's not what the callers expect. If scsi_device_quiesce() and
scsi_device_resume() are called concurrently that would be even worse. I think
we *really* should know whether callers serialize scsi_device_quiesce() and
scsi_device_resume() calls properly. Hence the WARN_ON_ONCE() statement.
Bart.
next prev parent reply other threads:[~2017-10-17 20:08 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-16 23:28 [PATCH v9 00/10] block, scsi, md: Improve suspend and resume Bart Van Assche
2017-10-16 23:28 ` [PATCH v9 01/10] md: Rename md_notifier into md_reboot_notifier Bart Van Assche
2017-10-17 6:23 ` Hannes Reinecke
2017-10-16 23:28 ` [PATCH v9 02/10] md: Introduce md_stop_all_writes() Bart Van Assche
2017-10-17 6:23 ` Hannes Reinecke
2017-10-16 23:28 ` [PATCH v9 03/10] md: Neither resync nor reshape while the system is frozen Bart Van Assche
2017-10-17 6:24 ` Hannes Reinecke
2017-10-16 23:28 ` [PATCH v9 04/10] block: Make q_usage_counter also track legacy requests Bart Van Assche
2017-10-17 6:25 ` Hannes Reinecke
2017-10-16 23:29 ` [PATCH v9 05/10] block: Introduce blk_get_request_flags() Bart Van Assche
2017-10-17 6:26 ` Hannes Reinecke
2017-10-16 23:29 ` [PATCH v9 06/10] block: Introduce BLK_MQ_REQ_PREEMPT Bart Van Assche
2017-10-17 6:26 ` Hannes Reinecke
2017-10-16 23:29 ` [PATCH v9 07/10] ide, scsi: Tell the block layer at request allocation time about preempt requests Bart Van Assche
2017-10-17 4:12 ` Martin K. Petersen
2017-10-17 6:27 ` Hannes Reinecke
2017-10-16 23:29 ` [PATCH v9 08/10] block: Add the QUEUE_FLAG_PREEMPT_ONLY request queue flag Bart Van Assche
2017-10-17 6:27 ` Hannes Reinecke
2017-10-16 23:29 ` [PATCH v9 09/10] block, scsi: Make SCSI quiesce and resume work reliably Bart Van Assche
2017-10-17 0:43 ` Ming Lei
2017-10-17 20:08 ` Bart Van Assche [this message]
2017-10-17 20:08 ` Bart Van Assche
2017-10-17 4:17 ` Martin K. Petersen
2017-10-17 6:33 ` Hannes Reinecke
2017-10-17 10:43 ` Ming Lei
2017-10-17 20:18 ` Bart Van Assche
2017-10-17 20:18 ` Bart Van Assche
2017-10-18 5:58 ` Hannes Reinecke
2017-10-16 23:29 ` [PATCH v9 10/10] block, nvme: Introduce blk_mq_req_flags_t Bart Van Assche
2017-10-17 6:34 ` Hannes Reinecke
2017-10-17 6:34 ` Hannes Reinecke
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=1508270897.3457.7.camel@wdc.com \
--to=bart.vanassche@wdc.com \
--cc=axboe@kernel.dk \
--cc=hare@suse.com \
--cc=hch@lst.de \
--cc=jthumshirn@suse.de \
--cc=linux-block@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=martin.petersen@oracle.com \
--cc=ming.lei@redhat.com \
--cc=oleksandr@natalenko.name \
/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.