From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 2839A6B0201 for ; Thu, 19 Aug 2010 20:08:58 -0400 (EDT) Received: from m5.gw.fujitsu.co.jp ([10.0.50.75]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o7K08snI030060 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Fri, 20 Aug 2010 09:08:54 +0900 Received: from smail (m5 [127.0.0.1]) by outgoing.m5.gw.fujitsu.co.jp (Postfix) with ESMTP id 73ADA45DE4F for ; Fri, 20 Aug 2010 09:08:54 +0900 (JST) Received: from s5.gw.fujitsu.co.jp (s5.gw.fujitsu.co.jp [10.0.50.95]) by m5.gw.fujitsu.co.jp (Postfix) with ESMTP id 4AFD145DE54 for ; Fri, 20 Aug 2010 09:08:54 +0900 (JST) Received: from s5.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s5.gw.fujitsu.co.jp (Postfix) with ESMTP id 137211DB803C for ; Fri, 20 Aug 2010 09:08:54 +0900 (JST) Received: from ml13.s.css.fujitsu.com (ml13.s.css.fujitsu.com [10.249.87.103]) by s5.gw.fujitsu.co.jp (Postfix) with ESMTP id B068DE08003 for ; Fri, 20 Aug 2010 09:08:53 +0900 (JST) From: KOSAKI Motohiro Subject: Re: oom: __task_cred() need rcu_read_lock() In-Reply-To: <7682.1282230394@redhat.com> References: <20100819220338.5FD5.A69D9226@jp.fujitsu.com> <7682.1282230394@redhat.com> Message-Id: <20100820084820.5FDB.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Fri, 20 Aug 2010 09:08:52 +0900 (JST) Sender: owner-linux-mm@kvack.org To: David Howells Cc: kosaki.motohiro@jp.fujitsu.com, "Paul E. McKenney" , LKML , linux-mm , Andrew Morton , David Rientjes , KAMEZAWA Hiroyuki List-ID: Hi > KOSAKI Motohiro wrote: > > > dump_tasks() can call __task_cred() safely because we are holding > > tasklist_lock. but rcu lock validator don't have enough knowledge and > > it makes following annoying warning. > > No, it can't. The tasklist_lock is not protection against the creds changing > on another CPU. Thank you for correction. I suppose you mean I missed CONFIG_TREE_PREEMPT_RCU, right? As far as my grepping, other rcu implementation and spinlock use preempt_disable(). In other word, Can I assume usual distro user don't hit this issue? Thanks. -- 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