From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: Re: [PATCH 2/3] don't take cgroup_mutex in destroy() Date: Fri, 20 Apr 2012 08:30:23 +0800 Message-ID: <4F90AE1F.7030304@huawei.com> References: <1334875758-20939-1-git-send-email-glommer@parallels.com> <1334875758-20939-3-git-send-email-glommer@parallels.com> <20120419225704.GE10553@google.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7BIT Return-path: In-reply-to: <20120419225704.GE10553-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Tejun Heo Cc: Glauber Costa , netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org, David Miller , devel-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, Vivek Goyal Tejun Heo wrote: > On Thu, Apr 19, 2012 at 07:49:17PM -0300, Glauber Costa wrote: >> Most of the destroy functions are only doing very simple things >> like freeing memory. >> >> The ones who goes through lists and such, already use its own >> locking for those. >> >> * The cgroup itself won't go away until we free it, (after destroy) >> * The parent won't go away because we hold a reference count >> * There are no more tasks in the cgroup, and the cgroup is declared >> dead (cgroup_is_removed() == true) >> >> For the blk-cgroup and the cpusets, I got the impression that the mutex >> is still necessary. >> >> For those, I grabbed it from within the destroy function itself. >> >> If the maintainer for those subsystems consider it safe to remove >> it, we can discuss it separately. > > I really don't like cgroup_lock() usage spreading more. It's > something which should be contained in cgroup.c proper. I looked at > the existing users a while ago and they seemed to be compensating > deficencies in API, so, if at all possible, let's not spread the > disease. > Agreed. I used to do cleanups to remove cgroup_lock()s in subsystems which are really not necessary.