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 394166B01F1 for ; Tue, 6 Apr 2010 07:42:44 -0400 (EDT) Date: Tue, 6 Apr 2010 19:42:35 +0800 From: anfei 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> Sender: owner-linux-mm@kvack.org 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 List-ID: 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); > > -- 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