Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752935Ab0LWMMU (ORCPT ); Thu, 23 Dec 2010 07:12:20 -0500 Received: from canuck.infradead.org ([134.117.69.58]:49976 "EHLO canuck.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752864Ab0LWMMS convert rfc822-to-8bit (ORCPT ); Thu, 23 Dec 2010 07:12:18 -0500 Subject: Re: [PATCH] avoid race condition in pick_next_task_fair in kernel/sched_fair.c From: Peter Zijlstra To: Yong Zhang Cc: Miklos Vajna , Mike Galbraith , shenghui , kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@elte.hu, Greg KH , Paul Turner In-Reply-To: References: <1277808215.1868.5.camel@laptop> <20101219020313.GJ31750@genesis.frugalware.org> <20101222002248.GP10557@genesis.frugalware.org> <1293006589.2170.41.camel@laptop> <1293007311.11370.172.camel@marge.simson.net> <1293008842.2170.70.camel@laptop> <20101222133154.GS10557@genesis.frugalware.org> <1293026422.2170.136.camel@laptop> <1293027112.2170.140.camel@laptop> <20101222151434.GW10557@genesis.frugalware.org> <1293037718.2170.155.camel@laptop> <1293050173.2170.389.camel@laptop> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Thu, 23 Dec 2010 13:12:10 +0100 Message-ID: <1293106330.2170.618.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1423 Lines: 26 On Thu, 2010-12-23 at 10:08 +0800, Yong Zhang wrote: > > systemd--1251 0d..5. 2015398us : enqueue_task_fair <-enqueue_task > > systemd--1251 0d..5. 2015398us : print_runqueue <-enqueue_task_fair > > systemd--1251 0d..5. 2015399us : __print_runqueue: cfs_rq: c2407c34, nr: 3, load: 3072 > > systemd--1251 0d..5. 2015400us : __print_runqueue: curr: f6a8de5c, comm: systemd-cgroups/1251, load: 1024 > > systemd--1251 0d..5. 2015401us : __print_runqueue: se: f69e6300, load: 1024, > > systemd--1251 0d..5. 2015401us : __print_runqueue: cfs_rq: f69e6540, nr: 2, load: 2048 > > systemd--1251 0d..5. 2015402us : __print_runqueue: curr: (null) > > systemd--1251 0d..5. 2015402us : __print_runqueue: se: f69e65a0, load: 4137574976, > > the load == f69e65a0 == address of se, odd This appears to be consistently true, I've also found that in between these two prints, there is a free_sched_group() freeing that exact entry. So post-print is a use-after-free artifact. What's interesting is that its freeing a cfs_rq struct with nr_running=1, that should not be possible... /me goes stare at the whole cgroup task attach vs cgroup destruction muck. -- 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/