From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Weiner Subject: Re: [patch for-3.12] mm, memcg: protect mem_cgroup_read_events for cpu hotplug Date: Tue, 1 Oct 2013 22:22:27 -0400 Message-ID: <20131002022227.GR856@cmpxchg.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: David Rientjes Cc: Linus Torvalds , Andrew Morton , Michal Hocko , KAMEZAWA Hiroyuki , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-mm.kvack.org On Tue, Oct 01, 2013 at 04:31:23PM -0700, David Rientjes wrote: > for_each_online_cpu() needs the protection of {get,put}_online_cpus() so > cpu_online_mask doesn't change during the iteration. There is no problem report here. Is there a crash? If it's just accuracy of the read, why would we care about some inaccuracies in counters that can change before you even get the results to userspace? And care to the point where we hold up CPU hotplugging for this? Also, the fact that you directly sent this to Linus suggests there is some urgency for this fix. What's going on? Thanks, Johannes