From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: Re: [PATCH v2] cgroup: protect modifications to cgroup->idr with cgroup_mutex Date: Wed, 12 Feb 2014 15:02:10 +0800 Message-ID: <52FB1C72.60605@huawei.com> References: <52FB14A5.9030307@huawei.com> <20140212063713.GA7984@mtj.dyndns.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140212063713.GA7984-9pTldWuhBndy/B6EtB590w@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Tejun Heo Cc: Michal Hocko , LKML , Cgroups On 2014/2/12 14:37, Tejun Heo wrote: > Hello, Li. > > On Wed, Feb 12, 2014 at 02:28:53PM +0800, Li Zefan wrote: >> v2: >> - Don't call deactivate_super() inside cgroup_mutex, as cgroup_kill_sb() >> will be called if sb refcnt reaches 0. I don't think this can happen, >> as cgroup_create() is called through vfs, so vfs should guarantee the >> superblock won't disappear. Still better not depend on it even my guess >> is probably correct. > > If the deadlock can't actually happen, I don't really care either way > as the code goes away after kernfs conversion anyway. I've already > applied v1, so if you think this change is important, can you send an > incremental patch? > I'm fine to stick with V1. I'm pretty confident it's safe, as we can increment sb refcnt without any checking or locking (even cgroup_mutex as the comment says) in cgroup_create().