From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d28relay04.in.ibm.com (d28relay04.in.ibm.com [9.184.220.61]) by e28smtp04.in.ibm.com (8.13.1/8.13.1) with ESMTP id mBA8BMfE012981 for ; Wed, 10 Dec 2008 13:41:22 +0530 Received: from d28av04.in.ibm.com (d28av04.in.ibm.com [9.184.220.66]) by d28relay04.in.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id mBA8BOl0663784 for ; Wed, 10 Dec 2008 13:41:24 +0530 Received: from d28av04.in.ibm.com (loopback [127.0.0.1]) by d28av04.in.ibm.com (8.13.1/8.13.3) with ESMTP id mBA8BL4H023839 for ; Wed, 10 Dec 2008 19:11:22 +1100 Date: Wed, 10 Dec 2008 13:41:14 +0530 From: Balbir Singh Subject: Re: [RFC][RFT] memcg fix cgroup_mutex deadlock when cpuset reclaims memory Message-ID: <20081210081114.GB25467@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20081210051947.GH7593@balbir.in.ibm.com> <20081210151948.9a83f70a.nishimura@mxp.nes.nec.co.jp> <20081210164126.8b3be761.nishimura@mxp.nes.nec.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20081210164126.8b3be761.nishimura@mxp.nes.nec.co.jp> Sender: owner-linux-mm@kvack.org Return-Path: To: Daisuke Nishimura Cc: menage@google.com, KAMEZAWA Hiroyuki , Daisuke Miyakawa , YAMAMOTO Takashi , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: * Daisuke Nishimura [2008-12-10 16:41:26]: > On Wed, 10 Dec 2008 15:19:48 +0900, Daisuke Nishimura wrote: > > On Wed, 10 Dec 2008 10:49:47 +0530, Balbir Singh wrote: > > > Hi, > > > > > > Here is a proposed fix for the memory controller cgroup_mutex deadlock > > > reported. It is lightly tested and reviewed. I need help with review > > > and test. Is the reported deadlock reproducible after this patch? A > > > careful review of the cpuset impact will also be highly appreciated. > > > > > > From: Balbir Singh > > > > > > cpuset_migrate_mm() holds cgroup_mutex throughout the duration of > > > do_migrate_pages(). The issue with that is that > > > > > > 1. It can lead to deadlock with memcg, as do_migrate_pages() > > > enters reclaim > > > 2. It can lead to long latencies, preventing users from creating/ > > > destroying other cgroups anywhere else > > > > > > The patch holds callback_mutex through the duration of cpuset_migrate_mm() and > > > gives up cgroup_mutex while doing so. > > > > > I agree changing cpuset_migrate_mm not to hold cgroup_mutex to fix the dead lock > > is one choice, and it looks good to me at the first impression. > > > > But I'm not sure it's good to change cpuset(other subsystem) code because of memcg. > > > > Anyway, I'll test this patch and report the result tomorrow. > > (Sorry, I don't have enough time today.) > > > Unfortunately, this patch doesn't seem enough. > > This patch can fix dead lock caused by "circular lock of cgroup_mutex", > but cannot that of caused by "race between page reclaim and cpuset_attach(mpol_rebind_mm)". > > (The dead lock I fixed in memcg-avoid-dead-lock-caused-by-race-between-oom-and-cpuset_attach.patch > was caused by "race between memcg's oom and mpol_rebind_mm, and was independent of hierarchy.) > Yes, I agree, my point was to fix the deadlock caused in the hierarchy due to cpuset_migrate_mm(). If I understand correctly 1. This patch introduces no new bug, but the old bug remains. The deadlock is fixed 2. We need this patch + your fix to completely solve the problem? Could you also share how to reproduce the issue, I'll test on my end as well. Thanks for your help! -- Balbir -- 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