From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 1/8] cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs Date: Wed, 31 Oct 2012 10:22:37 -0700 Message-ID: <20121031172237.GI2945@htj.dyndns.org> References: <1351657365-25055-1-git-send-email-tj@kernel.org> <1351657365-25055-2-git-send-email-tj@kernel.org> <20121031143751.GA22809@dhcp22.suse.cz> <20121031164123.GD2945@htj.dyndns.org> <20121031164855.GI22809@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20121031164855.GI22809-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Michal Hocko Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: containers.vger.kernel.org Hey, Michal. On Wed, Oct 31, 2012 at 05:48:55PM +0100, Michal Hocko wrote: > > The WARN_ON_ONCE() is just moved from the original > > cgroup_call_pre_destroy(). We can add an error out there but that > > makes future changes difficult. It's a chicken and egg problem. You > > gotta break the loop somewhere. > > I do not think this is that hard. You can simply change the return path > on pre_destroy error by BUG_ON in "cgroup: deactivate CSS's and mark > cgroup dead before invoking ->pre_destroy()". There is no chicke&egg > problem here because once the group is marked dead and css frozen then > the existing callbacks cannot possibly fail. > Or am I missing your point? I want to be able to move code verbatim in the later patch when relocating ->pre_destroy() invocations. Hmmm... alright, I'll make it break out of pre_destroy() here and change it to WARN_ON_ONCE() later on. Thanks. -- tejun