From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: Re: [PATCH 3/8] cgroup: use cgroup_lock_live_group(parent) in cgroup_create() Date: Mon, 5 Nov 2012 13:36:14 +0800 Message-ID: <5097504E.60809@huawei.com> References: <1351712650-23709-1-git-send-email-tj@kernel.org> <1351712650-23709-4-git-send-email-tj@kernel.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1351712650-23709-4-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Tejun Heo Cc: hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, mhocko-AlSwsSmVLrQ@public.gmane.org, bsingharora-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On 2012/11/1 3:44, Tejun Heo wrote: > This patch makes cgroup_create() fail if @parent is marked removed. > This is to prepare for further updates to cgroup_rmdir() path. > > Note that this change isn't strictly necessary. cgroup can only be > created via mkdir and the removed marking and dentry removal happen > without releasing cgroup_mutex, so cgroup_create() can never race with > cgroup_rmdir(). Even after the scheduled updates to cgroup_rmdir(), > cgroup_mkdir() and cgroup_rmdir() are synchronized by i_mutex > rendering the added liveliness check unnecessary. > > Do it anyway such that locking is contained inside cgroup proper and > we don't get nasty surprises if we ever grow another caller of > cgroup_create(). > > Signed-off-by: Tejun Heo > Reviewed-by: Michal Hocko Acked-by: Li Zefan