Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751480AbaJPKE6 (ORCPT ); Thu, 16 Oct 2014 06:04:58 -0400 Received: from relay.parallels.com ([195.214.232.42]:43767 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751239AbaJPKE5 (ORCPT ); Thu, 16 Oct 2014 06:04:57 -0400 Message-ID: <1413453893.24793.74.camel@tkhai> Subject: Re: [PATCH RFC] sched: Revert delayed_put_task_struct() and fix use after free From: Kirill Tkhai To: Peter Zijlstra CC: Kirill Tkhai , Oleg Nesterov , , Ingo Molnar , "Vladimir Davydov" Date: Thu, 16 Oct 2014 14:04:53 +0400 In-Reply-To: <1413453115.24793.73.camel@tkhai> 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> <20141016094333.GJ7369@worktop.fdxtended.com> <1413453002.24793.72.camel@tkhai> <1413453115.24793.73.camel@tkhai> Organization: Parallels Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.8.5-2+b3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Originating-IP: [10.30.26.172] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org В Чт, 16/10/2014 в 13:51 +0400, Kirill Tkhai пишет: > В Чт, 16/10/2014 в 13:50 +0400, Kirill Tkhai пишет: > > В Чт, 16/10/2014 в 11:43 +0200, Peter Zijlstra пишет: > > > 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. > > > > I mean p can be moved to other cpu. > > > > tsk = ACCESS_ONCE(cpu_rq(cpu)->curr); > > > > tsk is not p, (i.e current) here. > > Maybe I undestand wrong and preemption is disabled in memory fault? Ah, I found pagefault_disable(). No questions. -- 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/