From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755828AbZELJiq (ORCPT ); Tue, 12 May 2009 05:38:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754028AbZELJig (ORCPT ); Tue, 12 May 2009 05:38:36 -0400 Received: from gir.skynet.ie ([193.1.99.77]:37327 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752208AbZELJif (ORCPT ); Tue, 12 May 2009 05:38:35 -0400 Date: Tue, 12 May 2009 10:38:32 +0100 From: Mel Gorman To: David Rientjes Cc: Andrew Morton , Greg Kroah-Hartman , Nick Piggin , Peter Ziljstra , Christoph Lameter , Dave Hansen , San Mehat , Arve Hj?nnev?g , linux-kernel@vger.kernel.org Subject: Re: [patch 05/11 -mmotm] oom: fix possible oom_dump_tasks NULL pointer Message-ID: <20090512093832.GC25923@csn.ul.ie> References: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 10, 2009 at 03:07:16PM -0700, David Rientjes wrote: > When /proc/sys/vm/oom_dump_tasks is enabled, it is possible to get a NULL > pointer for tasks that have detached mm's since task_lock() is not held > during the tasklist scan. > > Acked-by: Nick Piggin > Signed-off-by: David Rientjes Minor nit. The Acked-by should come after the Signed-off-by. The window during which p->mm was a valid point and become an invalid one is *extremely* small but sure, it's there. Acked-by: Mel Gorman I would have preferred if the core VM patches were in a different set to the driver patches. Maybe there is an interdependency later but this patch at least looks standalone. > --- > mm/oom_kill.c | 24 +++++++++++++++--------- > 1 files changed, 15 insertions(+), 9 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -284,22 +284,28 @@ static void dump_tasks(const struct mem_cgroup *mem) > printk(KERN_INFO "[ pid ] uid tgid total_vm rss cpu oom_adj " > "name\n"); > do_each_thread(g, p) { > - /* > - * total_vm and rss sizes do not exist for tasks with a > - * detached mm so there's no need to report them. > - */ > - if (!p->mm) > - continue; > + struct mm_struct *mm; > + > if (mem && !task_in_mem_cgroup(p, mem)) > continue; > if (!thread_group_leader(p)) > continue; > > task_lock(p); > + mm = p->mm; > + if (!mm) { > + /* > + * total_vm and rss sizes do not exist for tasks with no > + * mm so there's no need to report them; they can't be > + * oom killed anyway. > + */ > + task_unlock(p); > + continue; > + } > printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d %3d %s\n", > - p->pid, __task_cred(p)->uid, p->tgid, > - p->mm->total_vm, get_mm_rss(p->mm), (int)task_cpu(p), > - p->oomkilladj, p->comm); > + p->pid, __task_cred(p)->uid, p->tgid, mm->total_vm, > + get_mm_rss(mm), (int)task_cpu(p), p->oomkilladj, > + p->comm); > task_unlock(p); > } while_each_thread(g, p); > } > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab