From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id 9535C6B01EE for ; Wed, 31 Mar 2010 05:18:37 -0400 (EDT) Date: Wed, 31 Mar 2010 11:16:28 +0200 From: Oleg Nesterov Subject: Re: [PATCH] oom: fix the unsafe proc_oom_score()->badness() call Message-ID: <20100331091628.GA11438@redhat.com> References: <1269447905-5939-1-git-send-email-anfei.zhou@gmail.com> <20100326150805.f5853d1c.akpm@linux-foundation.org> <20100326223356.GA20833@redhat.com> <20100328145528.GA14622@desktop> <20100328162821.GA16765@redhat.com> <20100329112111.GA16971@redhat.com> <20100330163909.GA16884@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org To: David Rientjes Cc: Andrew Morton , anfei , KOSAKI Motohiro , nishimura@mxp.nes.nec.co.jp, KAMEZAWA Hiroyuki , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On 03/30, David Rientjes wrote: > > On Tue, 30 Mar 2010, Oleg Nesterov wrote: > > > proc_oom_score(task) have a reference to task_struct, but that is all. > > If this task was already released before we take tasklist_lock > > > > - we can't use task->group_leader, it points to nowhere > > > > - it is not safe to call badness() even if this task is > > ->group_leader, has_intersects_mems_allowed() assumes > > it is safe to iterate over ->thread_group list. > > > > Add the pid_alive() check to ensure __unhash_process() was not called. > > > > Note: I think we shouldn't use ->group_leader, badness() should return > > the same result for any sub-thread. However this is not true currently, > > and I think that ->mm check and list_for_each_entry(p->children) in > > badness are not right. > > > > I think it would be better to just use task and not task->group_leader. Sure, agreed. I preserved ->group_leader just because I didn't understand why the current code doesn't use task. But note that pid_alive() is still needed. I'll check the code in -mm and resend. Oleg. -- 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