From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754740Ab0DFLmt (ORCPT ); Tue, 6 Apr 2010 07:42:49 -0400 Received: from mail-gw0-f46.google.com ([74.125.83.46]:33273 "EHLO mail-gw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753640Ab0DFLmn (ORCPT ); Tue, 6 Apr 2010 07:42:43 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=fJZj53mD5JiodzDQHKB5rZ/Ef4Hpv8WZYaKb7y9AVztJ8U8zvuuo4PvKoPBSMCltQS EHlR7mbpivoPrX62+vBR7VmHTj8bHaLl+gsoUrXvDT/PBKOOla3dVP1s39NQ8cP1FC6k W7o75rZ67VAZPCoPnXxuTeBpZmJawA6s5IBGM= Date: Tue, 6 Apr 2010 19:42:35 +0800 From: anfei To: Oleg Nesterov Cc: David Rientjes , Andrew Morton , KOSAKI Motohiro , nishimura@mxp.nes.nec.co.jp, KAMEZAWA Hiroyuki , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH -mm 2/4] oom: select_bad_process: PF_EXITING check should take ->mm into account Message-ID: <20100406114235.GA3965@desktop> References: <20100330154659.GA12416@redhat.com> <20100331175836.GA11635@redhat.com> <20100331204718.GD11635@redhat.com> <20100401135927.GA12460@redhat.com> <20100402111406.GA4432@redhat.com> <20100402183057.GA31723@redhat.com> <20100402183216.GC31723@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100402183216.GC31723@redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 02, 2010 at 08:32:16PM +0200, Oleg Nesterov wrote: > select_bad_process() checks PF_EXITING to detect the task which > is going to release its memory, but the logic is very wrong. > > - a single process P with the dead group leader disables > select_bad_process() completely, it will always return > ERR_PTR() while P can live forever > > - if the PF_EXITING task has already released its ->mm > it doesn't make sense to expect it is goiing to free > more memory (except task_struct/etc) > > Change the code to ignore the PF_EXITING tasks without ->mm. > > Signed-off-by: Oleg Nesterov > --- > > mm/oom_kill.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- MM/mm/oom_kill.c~2_FIX_PF_EXITING 2010-04-02 18:51:05.000000000 +0200 > +++ MM/mm/oom_kill.c 2010-04-02 18:58:37.000000000 +0200 > @@ -322,7 +322,7 @@ static struct task_struct *select_bad_pr > * the process of exiting and releasing its resources. > * Otherwise we could get an easy OOM deadlock. > */ > - if (p->flags & PF_EXITING) { > + if ((p->flags & PF_EXITING) && p->mm) { Even this check is satisfied, it still can't say p is a good victim or it will release memory automatically if multi threaded, as the exiting of p doesn't mean the other threads are going to exit, so the ->mm won't be released. > if (p != current) > return ERR_PTR(-1UL); > >