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From: Tejun Heo <tj@kernel.org>
To: Yu Kuai <yukuai1@huaweicloud.com>
Cc: hch@infradead.org, josef@toxicpanda.com, axboe@kernel.dk,
	cgroups@vger.kernel.org, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, yi.zhang@huawei.com,
	yangerkun@huawei.com, "yukuai (C)" <yukuai3@huawei.com>
Subject: Re: [PATCH -next 3/4] block/rq_qos: use a global mutex to protect rq_qos apis
Date: Thu, 5 Jan 2023 08:34:17 -1000	[thread overview]
Message-ID: <Y7cYKdOwSlfHtj7t@slm.duckdns.org> (raw)
In-Reply-To: <df2f7a60-467f-08ce-2a3e-1dc7853424aa@huaweicloud.com>

Hello,

On Thu, Jan 05, 2023 at 09:35:21AM +0800, Yu Kuai wrote:
> > Can you please take a look at the following patchset I just posted:
> > 
> >    https://lkml.kernel.org/r/20230105002007.157497-1-tj@kernel.org
> > 
> > After that, all these configuration operations are wrapped between
> > blkg_conf_init() and blkg_conf_exit() which probably are the right place to
> > implement the synchronization.
> 
> I see that, blkg_conf_init() and blkg_conf_exit() is good, however there
> are some details I want to confirm:
> 
> 1) rq_qos_add() can be called from iocost/iolatency, where
> blkg_conf_init() will be called first, while rq_qos_add() can also be
> called from wbt, where there is no blkg_conf_init(). Hence it seems to
> me we need two locks here, one to protect rq_qos apis; one to
> synchronize policy configuration and device removal.

wbt's lazy init is tied to one of the block device sysfs files, right? So,
it *should* already be protected against device removal.

Thanks.

-- 
tejun

  reply	other threads:[~2023-01-05 18:35 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-04  8:53 [PATCH -next 0/4] block/rq_qos: protect rq_qos apis with global mutex Yu Kuai
2023-01-04  8:53 ` [PATCH -next 1/4] block/rq_qos: move implementions of init/exit rq-qos apis to blk-rq-qos.c Yu Kuai
2023-01-04 21:30   ` Tejun Heo
2023-01-04  8:53 ` [PATCH -next 2/4] block/rq_qos: factor out a helper to add rq_qos and activate policy Yu Kuai
2023-01-04  8:53 ` [PATCH -next 3/4] block/rq_qos: use a global mutex to protect rq_qos apis Yu Kuai
2023-01-04 21:39   ` Tejun Heo
2023-01-05  0:28     ` Tejun Heo
2023-01-05  1:35       ` Yu Kuai
2023-01-05 18:34         ` Tejun Heo [this message]
2023-01-06  1:33           ` Yu Kuai
2023-01-06 18:23             ` Tejun Heo
2023-01-09  1:38               ` Yu Kuai
2023-01-09  6:37                 ` Yu Kuai
2023-01-04  8:53 ` [PATCH -next 4/4] block/rq_qos: fail rq_qos_add() after rq_qos_exit() Yu Kuai

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