From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 6B8096B004A for ; Fri, 10 Jun 2011 01:29:06 -0400 (EDT) Received: from m2.gw.fujitsu.co.jp (unknown [10.0.50.72]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id 200A83EE0C1 for ; Fri, 10 Jun 2011 14:29:01 +0900 (JST) Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 0019745DEA3 for ; Fri, 10 Jun 2011 14:29:01 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id CC3FE45DE83 for ; Fri, 10 Jun 2011 14:29:00 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id BF0B01DB803F for ; Fri, 10 Jun 2011 14:29:00 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.240.81.134]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 88ACB1DB8038 for ; Fri, 10 Jun 2011 14:29:00 +0900 (JST) Date: Fri, 10 Jun 2011 14:22:03 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH] [BUGFIX] update mm->owner even if no next owner. Message-Id: <20110610142203.f2d6c922.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: References: <20110609212956.GA2319@redhat.com> <20110610091355.2ce38798.kamezawa.hiroyu@jp.fujitsu.com> <20110610113311.409bb423.kamezawa.hiroyu@jp.fujitsu.com> <20110610121949.622e4629.kamezawa.hiroyu@jp.fujitsu.com> <20110610125551.385ea7ed.kamezawa.hiroyu@jp.fujitsu.com> <20110610133021.2eaaf0da.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Xiaotian Feng Cc: Hugh Dickins , Ying Han , Dave Jones , Linux Kernel , "linux-mm@kvack.org" , Oleg Nesterov , "akpm@linux-foundation.org" On Fri, 10 Jun 2011 13:21:46 +0800 Xiaotian Feng wrote: > On Fri, Jun 10, 2011 at 12:30 PM, KAMEZAWA Hiroyuki < > kamezawa.hiroyu@jp.fujitsu.com> wrote: > > > > > I think this can be a fix. > > maybe good to CC Oleg. > > == > > From dff52fb35af0cf36486965d19ee79e04b59f1dc4 Mon Sep 17 00:00:00 2001 > > From: KAMEZAWA Hiroyuki > > Date: Fri, 10 Jun 2011 13:15:14 +0900 > > Subject: [PATCH] [BUGFIX] update mm->owner even if no next owner. > > > > A panic is reported. > > > > > Call Trace: > > > [] mem_cgroup_from_task+0x15/0x17 > > > [] __mem_cgroup_try_charge+0x148/0x4b4 > > > [] ? need_resched+0x23/0x2d > > > [] ? preempt_schedule+0x46/0x4f > > > [] mem_cgroup_charge_common+0x9a/0xce > > > [] mem_cgroup_newpage_charge+0x5d/0x5f > > > [] khugepaged+0x5da/0xfaf > > > [] ? __init_waitqueue_head+0x4b/0x4b > > > [] ? add_mm_counter.constprop.5+0x13/0x13 > > > [] kthread+0xa8/0xb0 > > > [] ? sub_preempt_count+0xa1/0xb4 > > > [] kernel_thread_helper+0x4/0x10 > > > [] ? retint_restore_args+0x13/0x13 > > > [] ? __init_kthread_worker+0x5a/0x5a > > > > The code is. > > > return container_of(task_subsys_state(p, mem_cgroup_subsys_id), > > > struct mem_cgroup, css); > > > > > > What happens here is accssing a freed task struct "p" from mm->owner. > > So, it's doubtful that mm->owner points to freed task struct. > > > > > But from the bug itself, it looks more likely kernel is hitting a freed > p->cgroups, right? > If p is already freed, the kernel will fault on > 781cc62d: 8b 82 fc 08 00 00 mov 0x8fc(%edx),%eax > > Then you will not get a value of 6b6b6b87, right? %edx here is a pointer for task struct. Then, task->cgroup == 0x6b6b6b6b. It means "task" is freed. Thanks, -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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org