From: "tj@kernel.org" <tj@kernel.org>
To: Bart Van Assche <Bart.VanAssche@wdc.com>
Cc: "hch@lst.de" <hch@lst.de>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"00moses.alexander00@gmail.com" <00moses.alexander00@gmail.com>,
"axboe@kernel.dk" <axboe@kernel.dk>
Subject: Re: [PATCH] block: Ensure that a request queue is dissociated from the cgroup controller
Date: Thu, 12 Apr 2018 11:11:21 -0700 [thread overview]
Message-ID: <20180412181121.GA1911913@devbig577.frc2.facebook.com> (raw)
In-Reply-To: <f98af37ea6755119177c26fbb73b0071ddef90b8.camel@wdc.com>
Hello,
On Thu, Apr 12, 2018 at 04:29:09PM +0000, Bart Van Assche wrote:
> Any code that submits a bio or request needs blk_queue_enter() /
> blk_queue_exit() anyway. Please have a look at the following commit - you will
> see that that commit reduces the number of blk_queue_enter() / blk_queue_exit()
> calls in the hot path:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/commit/?h=for-linus&id=37f9579f4c31a6d698dbf3016d7bf132f9288d30
So, this can work, but it's still pretty fragile.
* Lock switching is fragile and we really should get rid of it. This
is very likely to come back and bite us.
* Right now, blk_queue_enter/exit() doesn't have any annotations.
IOW, there's no way for paths which need enter locked to actually
assert that. If we're gonna protect more things with queue
enter/exit, it gotta be annotated.
Thanks.
--
tejun
next prev parent reply other threads:[~2018-04-12 18:11 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-12 1:58 [PATCH] block: Ensure that a request queue is dissociated from the cgroup controller Bart Van Assche
2018-04-12 4:20 ` Alexandru Moise
2018-04-12 4:32 ` Alexandru Moise
2018-04-12 4:22 ` Alexandru Moise
2018-04-12 5:34 ` Christoph Hellwig
2018-04-12 11:52 ` Bart Van Assche
2018-04-12 13:14 ` hch
2018-04-12 13:48 ` tj
2018-04-12 13:56 ` hch
2018-04-12 13:58 ` tj
2018-04-12 14:07 ` tj
2018-04-12 13:51 ` Tejun Heo
2018-04-12 14:09 ` Bart Van Assche
2018-04-12 15:37 ` Tejun Heo
2018-04-12 16:03 ` Bart Van Assche
2018-04-12 16:12 ` tj
2018-04-12 16:29 ` Bart Van Assche
2018-04-12 18:11 ` tj [this message]
2018-04-12 18:56 ` Bart Van Assche
2018-04-12 19:09 ` tj
2018-04-12 22:40 ` Bart Van Assche
2018-04-13 15:18 ` tj
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