From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752194Ab2ISVod (ORCPT ); Wed, 19 Sep 2012 17:44:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:24030 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752001Ab2ISVoc (ORCPT ); Wed, 19 Sep 2012 17:44:32 -0400 Date: Wed, 19 Sep 2012 17:41:12 -0400 From: Dave Jones To: David Rientjes Cc: Linus Torvalds , Raghavendra K T , Greg Kroah-Hartman , Srivatsa Vaddagiri , Suzuki Poulose , Konrad Rzeszutek Wilk , Jeremy Fitzhardinge , linux-kernel@vger.kernel.org Subject: Re: 3.6rc6 slab corruption. Message-ID: <20120919214112.GA15027@redhat.com> Mail-Followup-To: Dave Jones , David Rientjes , Linus Torvalds , Raghavendra K T , Greg Kroah-Hartman , Srivatsa Vaddagiri , Suzuki Poulose , Konrad Rzeszutek Wilk , Jeremy Fitzhardinge , linux-kernel@vger.kernel.org References: <20120918143504.GA30585@redhat.com> <20120918185310.GA27689@redhat.com> <5059D015.2020104@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 19, 2012 at 02:27:37PM -0700, David Rientjes wrote: > On Wed, 19 Sep 2012, Linus Torvalds wrote: > > > > Create a 350 processes reading /sys/kernel/debug/kvm/spinlocks/histo_blocked > > > file simultaneously in while loop for more than 3 hours on my box. > > > > You need to open the file a single time, and then after that sinelg > > open (either threaded or with fork()) do multiple concurrent copies > > something like > > > > for (;;) { > > char buf[1024]; > > lseek(fd, 0, SEEK_SET); > > These are non-seekable files, so this will always fail. That makes the > race much more difficult to trigger: the read needs to call > u32_array_read() with both threads finding *ppos == 0 and then race > between the kfree() and resetting of file->private_data pointer. > > [ I'm surprised that Dave was able to trigger this so often that he has > 800MB of log. ] Brainfart. 800Kb. Still, lots. Dave