From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 8/9] cgroup_freezer: add ->post_create() and ->pre_destroy() and track online state Date: Thu, 8 Nov 2012 09:17:42 -0800 Message-ID: <20121108171742.GJ12973@htj.dyndns.org> References: <1351931915-1701-1-git-send-email-tj@kernel.org> <1351931915-1701-9-git-send-email-tj@kernel.org> <20121108132306.GH31821@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20121108132306.GH31821-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Michal Hocko Cc: lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, rjw-KKrjLPT3xs0@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org List-Id: linux-pm@vger.kernel.org Hello, On Thu, Nov 08, 2012 at 02:23:06PM +0100, Michal Hocko wrote: > On Sat 03-11-12 01:38:34, Tejun Heo wrote: > > A cgroup is online and visible to iteration between ->post_create() > > and ->pre_destroy(). This patch introduces CGROUP_FREEZER_ONLINE and > > toggles it from the newly added freezer_post_create() and > > freezer_pre_destroy() while holding freezer->lock such that a > > cgroup_freezer can be reilably distinguished to be online. This will > > be used by full hierarchy support. > > I am thinking whether freezer_pre_destroy is really needed. Once we > reach pre_destroy then there are no tasks nor any children in the group > so there is nobody to wake up if the group was frozen and the destroy > callback is called after synchronize_rcu so the traversing should be > safe. Yeah, it might be true, but I'd still like to keep the offlining in ->pre_destroy() so that it's symmetrical w/ ->post_create(). I'll rename and document the ops so that the roles of each are clearer. Thanks. -- tejun