From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id 769066B005C for ; Wed, 14 Jan 2009 23:53:34 -0500 (EST) Received: from m1.gw.fujitsu.co.jp ([10.0.50.71]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n0F4rWna018093 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Thu, 15 Jan 2009 13:53:32 +0900 Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 8035545DD74 for ; Thu, 15 Jan 2009 13:53:33 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.fujitsu.co.jp [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 639FC45DD72 for ; Thu, 15 Jan 2009 13:53:33 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id CAA8D1DB803A for ; Thu, 15 Jan 2009 13:53:31 +0900 (JST) Received: from m108.s.css.fujitsu.com (m108.s.css.fujitsu.com [10.249.87.108]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 4F8EA1DB803F for ; Thu, 15 Jan 2009 13:53:28 +0900 (JST) Date: Thu, 15 Jan 2009 13:52:23 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [RFC][PATCH 5/4] memcg: don't call res_counter_uncharge when obsolete Message-Id: <20090115135223.1789e639.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090115041750.GE21516@balbir.in.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> <20090115041750.GE21516@balbir.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: balbir@linux.vnet.ibm.com Cc: Daisuke Nishimura , LKML , linux-mm , Andrew Morton , Pavel Emelyanov , Li Zefan , Paul Menage List-ID: On Thu, 15 Jan 2009 09:47:50 +0530 Balbir Singh wrote: > * 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. > Write a shell script as following ? == TASKS=`cat /xxx/xxx/xxx/tasks` if [ -n $TASKS ]; then echo "there is alive tasks in group /xxx/xxx/xxx/" fi rmdir /xxx/xxx/xxx/ CODE=$? if [ $CODE = EBUSY ]; then investigate why.... fi == I don't want. I think rmdir() should succeed everywhen "there are no tasks and children". And that can be done. With Paul's suggestion, I'll add wait_queue for rmdir of cgroup. -Kame -- 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