From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH 1/8] cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs Date: Wed, 31 Oct 2012 21:14:16 +0100 Message-ID: <20121031201415.GG1271@dhcp22.suse.cz> References: <1351712650-23709-1-git-send-email-tj@kernel.org> <1351712650-23709-2-git-send-email-tj@kernel.org> <20121031200859.GE1271@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: List-Id: 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: Tejun Heo Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org On Wed 31-10-12 13:11:02, Tejun Heo wrote: > Hello, > > On Wed, Oct 31, 2012 at 1:08 PM, Michal Hocko wrote: > > local_irq_disable doesn't guarantee atomicity, because other CPUs will > > Maybe it should say atomicity on the local CPU. That would be more clear but being more verbose doesn't hurt either :P > > see the change in steps so this is a bit misleading. The real reason > > AFAICS is that we do not want to hang in css_tryget from IRQ context > > (does this really happen btw.?) which would interrupt cgroup_rmdir > > between we add CSS_DEACT_BIAS and the group is marked CGRP_REMOVED. > > Or am I still missing the point? > > Yeah, that's the correct one. We don't want tryget happening between > DEACT_BIAS and REMOVED as it can hang forever there. -- Michal Hocko SUSE Labs