Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751380Ab3FYR0b (ORCPT ); Tue, 25 Jun 2013 13:26:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48606 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751191Ab3FYR0a (ORCPT ); Tue, 25 Jun 2013 13:26:30 -0400 Date: Tue, 25 Jun 2013 13:26:09 -0400 From: Dave Jones To: Steven Rostedt Cc: Oleg Nesterov , "Paul E. McKenney" , Linux Kernel , Linus Torvalds , "Eric W. Biederman" , Andrey Vagin Subject: Re: frequent softlockups with 3.10rc6. Message-ID: <20130625172609.GA17050@redhat.com> Mail-Followup-To: Dave Jones , Steven Rostedt , Oleg Nesterov , "Paul E. McKenney" , Linux Kernel , Linus Torvalds , "Eric W. Biederman" , Andrey Vagin References: <20130623160452.GA11740@redhat.com> <20130624020014.GB12811@redhat.com> <20130624143928.GA20659@redhat.com> <1372085549.18733.162.camel@gandalf.local.home> <20130624160012.GB5993@redhat.com> <1372091079.18733.168.camel@gandalf.local.home> <20130624165140.GB8572@redhat.com> <1372093476.18733.170.camel@gandalf.local.home> <20130625165556.GA16170@redhat.com> <1372180890.18733.217.camel@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1372180890.18733.217.camel@gandalf.local.home> 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 Content-Length: 1268 Lines: 31 On Tue, Jun 25, 2013 at 01:21:30PM -0400, Steven Rostedt wrote: > On Tue, 2013-06-25 at 12:55 -0400, Dave Jones wrote: > > > While I've been spinning wheels trying to reproduce that softlockup bug, > > On another machine I've been refining my list-walk debug patch. > > I added an ugly "ok, the ringbuffer is playing games with lower two bits" special case. > > > > But what the hell is going on here ? > > > > next->prev should be prev (ffff88023c6cdd18), but was 00ffff88023c6cdd. (next=ffff880243288001). > > > > (trace comes from the same ringbuffer code) > > What's the above saying? ffff880243288000->prev == 00ffff88023c6cdd but > it should have been ffff88023c6cdd18? That is: ffff88023c6cdd18->next == > ffff880243288001? It's saying something has done >>8 on a pointer, and stuck it in a list head. > Not sure how that would mess up. The ring-buffer code has lots of > integrity checks to make sure nothing like this breaks. My integrity checks can beat up your integrity checks. Dav -- 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/