From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id 824596B005C for ; Wed, 14 Jan 2009 23:17:55 -0500 (EST) Received: from d28relay02.in.ibm.com (d28relay02.in.ibm.com [9.184.220.59]) by e28smtp09.in.ibm.com (8.13.1/8.13.1) with ESMTP id n0F44cb5001832 for ; Thu, 15 Jan 2009 09:34:38 +0530 Received: from d28av05.in.ibm.com (d28av05.in.ibm.com [9.184.220.67]) by d28relay02.in.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id n0F4Fwhm1937446 for ; Thu, 15 Jan 2009 09:45:58 +0530 Received: from d28av05.in.ibm.com (loopback [127.0.0.1]) by d28av05.in.ibm.com (8.13.1/8.13.3) with ESMTP id n0F4HlBw007303 for ; Thu, 15 Jan 2009 15:17:48 +1100 Date: Thu, 15 Jan 2009 09:47:50 +0530 From: Balbir Singh Subject: Re: [RFC][PATCH 5/4] memcg: don't call res_counter_uncharge when obsolete Message-ID: <20090115041750.GE21516@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20090113184533.6ffd2af9.nishimura@mxp.nes.nec.co.jp> <20090114175121.275ecd59.nishimura@mxp.nes.nec.co.jp> <20090114135539.GA21516@balbir.in.ibm.com> <20090115122416.e15d88a7.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20090115122416.e15d88a7.kamezawa.hiroyu@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: Daisuke Nishimura , LKML , linux-mm , Andrew Morton , Pavel Emelyanov , Li Zefan , Paul Menage List-ID: * KAMEZAWA Hiroyuki [2009-01-15 12:24:16]: > On Wed, 14 Jan 2009 19:25:39 +0530 > Balbir Singh wrote: > > > * Daisuke Nishimura [2009-01-14 17:51:21]: > > > > > This is a new one. Please review. > > > > > > === > > > From: Daisuke Nishimura > > > > > > mem_cgroup_get ensures that the memcg that has been got can be accessed > > > even after the directory has been removed, but it doesn't ensure that parents > > > of it can be accessed: parents might have been freed already by rmdir. > > > > > > This causes a bug in case of use_hierarchy==1, because res_counter_uncharge > > > climb up the tree. > > > > > > Check if the memcg is obsolete, and don't call res_counter_uncharge when obsole. > > > > > > Signed-off-by: Daisuke Nishimura > > > > I liked the earlier, EBUSY approach that ensured that parents could > > not go away if children exist. IMHO, the code has gotten too complex > > and has too many corner cases. Time to revisit it. > > > > But I don't like -EBUSY ;) > > When rmdir() returns -EBUSY even if there are no (visible) children and tasks, > our customer will take kdump and send it to me "please explain this kernel bug" > > I'm sure it will happen ;) > OK, but memory.stat can show why the group is busy and with move_to_parent() such issues should not occur right? I'll relook at the code. Thanks for your input. -- 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