From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 4/6] cgroups: forbid pre_destroy callback to fail Date: Fri, 19 Oct 2012 13:17:36 -0700 Message-ID: <20121019201736.GQ13370@google.com> References: <1350480648-10905-1-git-send-email-mhocko@suse.cz> <1350480648-10905-5-git-send-email-mhocko@suse.cz> <50811E5E.1090205@huawei.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; bh=RXGwCGy0eZuC3XKzo4P3ScIX5bwbLADIEXYpFsh8Bmk=; b=WN039gaeoyNY5u5oVqO8ueDzkALjrf6PSZrvPnvNoiu2ZYRZvzfVV4UKiS5HcW8hn5 I9bGl4BsWzZzqSLpVH/MT9/UYY+r2HACvwjEfogn4Qr3WjWBDPac//YYmt2OTGOkfME2 vCU8eWTu4pMDIgZWGj9FE6T3MQitt3n2YDFT3QH/yaU6lxpKB/n+aNQsrZuqx2yBDrZ0 wF47rRFfEFs6eb/ChYJzV78Q/OJWf3L4uX7luroLBJfnEurfXlBRlfy7e7gfFLSSeO95 KJm4LhqIQ9SBNuwPoZUe7PgOJCobvCOUoaYecQ3YH6nBGE0RK/G+f9STLiA4X3c/srk9 JlpQ== Content-Disposition: inline In-Reply-To: <50811E5E.1090205-hv44wF8Li93QT0dZR+AlfA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Li Zefan Cc: Michal Hocko , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Johannes Weiner , KAMEZAWA Hiroyuki , Balbir Singh On Fri, Oct 19, 2012 at 05:33:18PM +0800, Li Zefan wrote: > On 2012/10/17 21:30, Michal Hocko wrote: > > Now that mem_cgroup_pre_destroy callback doesn't fail finally we can > > safely move on and forbit all the callbacks to fail. The last missing > > piece is moving cgroup_call_pre_destroy after cgroup_clear_css_refs so > > that css_tryget fails so no new charges for the memcg can happen. > > > The callbacks are also called from within cgroup_lock to guarantee that > > no new tasks show up. > > I'm afraid this won't work. See commit 3fa59dfbc3b223f02c26593be69ce6fc9a940405 > ("cgroup: fix potential deadlock in pre_destroy") Yeah, you're right. Argh... we really should unexport cgroup_lock soon. Thanks. -- tejun From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx193.postini.com [74.125.245.193]) by kanga.kvack.org (Postfix) with SMTP id 841686B008A for ; Fri, 19 Oct 2012 16:17:41 -0400 (EDT) Received: by mail-pb0-f41.google.com with SMTP id rq2so754762pbb.14 for ; Fri, 19 Oct 2012 13:17:40 -0700 (PDT) Date: Fri, 19 Oct 2012 13:17:36 -0700 From: Tejun Heo Subject: Re: [PATCH 4/6] cgroups: forbid pre_destroy callback to fail Message-ID: <20121019201736.GQ13370@google.com> References: <1350480648-10905-1-git-send-email-mhocko@suse.cz> <1350480648-10905-5-git-send-email-mhocko@suse.cz> <50811E5E.1090205@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50811E5E.1090205@huawei.com> Sender: owner-linux-mm@kvack.org List-ID: To: Li Zefan Cc: Michal Hocko , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Johannes Weiner , KAMEZAWA Hiroyuki , Balbir Singh On Fri, Oct 19, 2012 at 05:33:18PM +0800, Li Zefan wrote: > On 2012/10/17 21:30, Michal Hocko wrote: > > Now that mem_cgroup_pre_destroy callback doesn't fail finally we can > > safely move on and forbit all the callbacks to fail. The last missing > > piece is moving cgroup_call_pre_destroy after cgroup_clear_css_refs so > > that css_tryget fails so no new charges for the memcg can happen. > > > The callbacks are also called from within cgroup_lock to guarantee that > > no new tasks show up. > > I'm afraid this won't work. See commit 3fa59dfbc3b223f02c26593be69ce6fc9a940405 > ("cgroup: fix potential deadlock in pre_destroy") Yeah, you're right. Argh... we really should unexport cgroup_lock soon. Thanks. -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759288Ab2JSURn (ORCPT ); Fri, 19 Oct 2012 16:17:43 -0400 Received: from mail-pa0-f46.google.com ([209.85.220.46]:53644 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755086Ab2JSURl (ORCPT ); Fri, 19 Oct 2012 16:17:41 -0400 Date: Fri, 19 Oct 2012 13:17:36 -0700 From: Tejun Heo To: Li Zefan Cc: Michal Hocko , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Johannes Weiner , KAMEZAWA Hiroyuki , Balbir Singh Subject: Re: [PATCH 4/6] cgroups: forbid pre_destroy callback to fail Message-ID: <20121019201736.GQ13370@google.com> References: <1350480648-10905-1-git-send-email-mhocko@suse.cz> <1350480648-10905-5-git-send-email-mhocko@suse.cz> <50811E5E.1090205@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50811E5E.1090205@huawei.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 19, 2012 at 05:33:18PM +0800, Li Zefan wrote: > On 2012/10/17 21:30, Michal Hocko wrote: > > Now that mem_cgroup_pre_destroy callback doesn't fail finally we can > > safely move on and forbit all the callbacks to fail. The last missing > > piece is moving cgroup_call_pre_destroy after cgroup_clear_css_refs so > > that css_tryget fails so no new charges for the memcg can happen. > > > The callbacks are also called from within cgroup_lock to guarantee that > > no new tasks show up. > > I'm afraid this won't work. See commit 3fa59dfbc3b223f02c26593be69ce6fc9a940405 > ("cgroup: fix potential deadlock in pre_destroy") Yeah, you're right. Argh... we really should unexport cgroup_lock soon. Thanks. -- tejun