From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx161.postini.com [74.125.245.161]) by kanga.kvack.org (Postfix) with SMTP id 0D74D6B0033 for ; Fri, 12 Jul 2013 14:48:41 -0400 (EDT) Received: by mail-ye0-f169.google.com with SMTP id m1so3290671yen.28 for ; Fri, 12 Jul 2013 11:48:41 -0700 (PDT) Date: Fri, 12 Jul 2013 11:48:36 -0700 From: Tejun Heo Subject: Re: [PATCH 1/3] vmpressure: document why css_get/put is not necessary for work queue based signaling Message-ID: <20130712184836.GC23680@mtj.dyndns.org> References: <20130712084039.GA13224@dhcp22.suse.cz> <1373621098-15261-1-git-send-email-mhocko@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1373621098-15261-1-git-send-email-mhocko@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: cgroups@vger.kernel.org, Li Zefan , Anton Vorontsov , Johannes Weiner , KAMEZAWA Hiroyuki , KOSAKI Motohiro , linux-mm@kvack.org On Fri, Jul 12, 2013 at 11:24:56AM +0200, Michal Hocko wrote: > Cgroup events are unregistered from the workqueue context by > cgroup_event_remove scheduled by cgroup_destroy_locked (when a cgroup is > removed by rmdir). > > cgroup_event_remove removes the eventfd wait queue from the work > queue, then it unregisters all the registered events and finally > puts a reference to the cgroup dentry. css_free which triggers memcg > deallocation is called after the last reference is dropped. > > The scheduled vmpressure work item either happens before > cgroup_event_remove or it is not triggered at all so it always happen > _before_ the last dput thus css_free. I don't follow what the above has to do with ensuring work item execution is finished before the underlying data structure is released. How are the above relevant? What am I missing here? > This patch just documents this trickiness. This doesn't have to be tricky at all. It's a *completely* routine thing. Would you please stop making it one? -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org