Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751531AbaJPJni (ORCPT ); Thu, 16 Oct 2014 05:43:38 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:39830 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750966AbaJPJng (ORCPT ); Thu, 16 Oct 2014 05:43:36 -0400 Date: Thu, 16 Oct 2014 11:43:33 +0200 From: Peter Zijlstra To: Kirill Tkhai Cc: Kirill Tkhai , Oleg Nesterov , linux-kernel@vger.kernel.org, Ingo Molnar , Vladimir Davydov Subject: Re: [PATCH RFC] sched: Revert delayed_put_task_struct() and fix use after free Message-ID: <20141016094333.GJ7369@worktop.fdxtended.com> References: <1413376300.24793.55.camel@tkhai> <20141015150641.GA2755@redhat.com> <20141015194044.GA4557@redhat.com> <543EEB1F.3040900@yandex.ru> <20141016075950.GC7369@worktop.fdxtended.com> <1413447404.24793.67.camel@tkhai> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1413447404.24793.67.camel@tkhai> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 16, 2014 at 12:16:44PM +0400, Kirill Tkhai wrote: > В Чт, 16/10/2014 в 09:59 +0200, Peter Zijlstra пишет: > > On Thu, Oct 16, 2014 at 01:46:07AM +0400, Kirill Tkhai wrote: > > > > --- x/kernel/sched/fair.c > > > > +++ x/kernel/sched/fair.c > > > > @@ -1165,7 +1165,7 @@ static void task_numa_compare(struct tas > > > > > > > > rcu_read_lock(); > > > > cur = ACCESS_ONCE(dst_rq->curr); > > > > - if (cur->pid == 0) /* idle */ > > > > + if (is_idle_task(cur) || (curr->flags & PF_EXITING)) > > > > cur = NULL; > > > > > > > > /* > > > > > > > > > > Looks like, we have to use the same fix for task_numa_group(). > > > > Don't think so, task_numa_group() is only called from task_numa_fault() > > which is on 'current' and neither idle and PF_EXITING should be > > faulting. > > Isn't task_numa_group() fully preemptible? Not seeing how that is relevant. > It seems cpu_rq(cpu)->curr is not always equal to p. It should be afaict: task_numa_fault() p = current; task_numa_group(p, ..); And like said, idle tasks and PF_EXITING task should never get (numa) faults for they should never be touching userspace. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/