From: Bart Van Assche <Bart.VanAssche@sandisk.com>
To: "tom.leiming@gmail.com" <tom.leiming@gmail.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"hch@infradead.org" <hch@infradead.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"yizhan@redhat.com" <yizhan@redhat.com>,
"axboe@fb.com" <axboe@fb.com>, "tj@kernel.org" <tj@kernel.org>
Subject: Re: [PATCH v1 3/3] blk-mq: start to freeze queue just after setting dying
Date: Fri, 17 Mar 2017 20:36:58 +0000 [thread overview]
Message-ID: <1489783004.2826.13.camel@sandisk.com> (raw)
In-Reply-To: <CACVXFVPF0Sx5HyU+xw0MyghYMWifZ0SDH0YCtM-jrhieOJOJGg@mail.gmail.com>
On Sat, 2017-03-18 at 02:32 +0800, Ming Lei wrote:
> On Sat, Mar 18, 2017 at 1:32 AM, Bart Van Assche wrote:
> > + /*
> > + * Avoid that the updates of the queue flags and q_usage_counter
> > + * are reordered.
> > + */
> > + smp_wmb();
>
> atomic_inc_return() in blk_mq_freeze_queue_start() does imply a
> barrier(smp_mb()).
Hello Ming,
It's probably a good idea to mention that in a comment. The implementation
of blk_mq_freeze_queue_start() namely could be changed in the future such
that it uses another atomic operation that doesn't implicitly perform smp_mb().
Thanks,
Bart.
next prev parent reply other threads:[~2017-03-17 20:39 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-17 9:57 [PATCH v1 0/3] blk-mq: dying queue fix & improvement Ming Lei
2017-03-17 9:57 ` [PATCH v1 1/3] blk-mq: don't complete un-started request in timeout handler Ming Lei
2017-03-18 11:24 ` Hannes Reinecke
2017-03-17 9:57 ` [PATCH v1 2/3] blk-mq: comment on races related with " Ming Lei
2017-03-17 17:39 ` Bart Van Assche
2017-03-17 18:23 ` Ming Lei
2017-03-18 11:25 ` Hannes Reinecke
2017-03-17 9:57 ` [PATCH v1 3/3] blk-mq: start to freeze queue just after setting dying Ming Lei
2017-03-17 17:32 ` Bart Van Assche
2017-03-17 18:32 ` Ming Lei
2017-03-17 20:36 ` Bart Van Assche [this message]
2017-03-17 23:26 ` Bart Van Assche
2017-03-18 1:01 ` Ming Lei
2017-03-18 11:27 ` Hannes Reinecke
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