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From: Tejun Heo <tj@kernel.org>
To: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: xuejiufei <jiufei.xue@linux.alibaba.com>,
	Jens Axboe <axboe@kernel.dk>,
	Caspar Zhang <caspar@linux.alibaba.com>,
	linux-block <linux-block@vger.kernel.org>,
	cgroups@vger.kernel.org
Subject: Re: [PATCH v2] blk-throttle: fix race between blkcg_bio_issue_check and cgroup_rmdir
Date: Sun, 4 Mar 2018 12:23:17 -0800	[thread overview]
Message-ID: <20180304202317.GC231488@devbig577.frc2.facebook.com> (raw)
In-Reply-To: <a74b1f86-1e54-cf07-9b53-773abbb9df33@linux.alibaba.com>

Hello, Joseph.

Sorry about late reply.

On Wed, Feb 28, 2018 at 02:52:10PM +0800, Joseph Qi wrote:
> In current code, I'm afraid pd_offline_fn() as well as the rest
> destruction have to be called together under the same blkcg->lock and
> q->queue_lock.
> For example, if we split the pd_offline_fn() and radix_tree_delete()
> into 2 phases, it may introduce a race between blkcg_deactivate_policy()
> when exit queue and blkcg_css_free(), which will result in
> pd_offline_fn() to be called twice.

So, yeah, the sync scheme aroung blkg is pretty brittle and we'd need
some restructuring to separate out blkg offlining and release, but it
looks like that'd be the right thing to do, no?

Thanks.

-- 
tejun

  reply	other threads:[~2018-03-04 20:23 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-07  8:40 [PATCH v2] blk-throttle: fix race between blkcg_bio_issue_check and cgroup_rmdir Joseph Qi
2018-02-07 21:38 ` Tejun Heo
2018-02-08  2:29   ` Joseph Qi
2018-02-08 15:23     ` Tejun Heo
2018-02-09  2:15       ` Joseph Qi
2018-02-12 17:11         ` Tejun Heo
2018-02-22  6:14           ` Joseph Qi
2018-02-22 15:18             ` Tejun Heo
2018-02-23  1:56               ` xuejiufei
2018-02-23 14:23                 ` Tejun Heo
2018-02-24  1:45                   ` Joseph Qi
2018-02-27  3:18                     ` Joseph Qi
2018-02-27 18:33                     ` Tejun Heo
2018-02-28  6:52                       ` Joseph Qi
2018-03-04 20:23                         ` Tejun Heo [this message]
2018-03-05  1:17                           ` Joseph Qi

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