Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757497AbaGWOZJ (ORCPT ); Wed, 23 Jul 2014 10:25:09 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:41070 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753028AbaGWOZH (ORCPT ); Wed, 23 Jul 2014 10:25:07 -0400 Date: Wed, 23 Jul 2014 16:24:54 +0200 From: Peter Zijlstra To: Dietmar Eggemann Cc: Michel =?iso-8859-1?Q?D=E4nzer?= , Linus Torvalds , Ingo Molnar , Linux Kernel Mailing List Subject: Re: Random panic in load_balance() with 3.16-rc Message-ID: <20140723142454.GQ12054@laptop.lan> References: <53CF31AE.30403@daenzer.net> <20140723064948.GK3935@laptop> <53CF6CC4.6090207@daenzer.net> <20140723082819.GR3935@laptop> <20140723092536.GO12054@laptop.lan> <53CF80EE.5050702@daenzer.net> <53CF844A.5050106@arm.com> <20140723111110.GT3935@laptop> <20140723113021.GP12054@laptop.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140723113021.GP12054@laptop.lan> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 23, 2014 at 01:30:21PM +0200, Peter Zijlstra wrote: > On Wed, Jul 23, 2014 at 01:11:10PM +0200, Peter Zijlstra wrote: > > On Wed, Jul 23, 2014 at 10:45:46AM +0100, Dietmar Eggemann wrote: > > > Doesn't the picture showing the captured panic reveal more information. > > > Haven't seen it myself, I just saw Peter's reply to your email > > > > Its a general protection fault from somewhere in load_balance(), I send > > you the picture. > > > > It would help to get addr2line of the RIP I suppose. > > > > Michel provided a config, so lemme go try and build that, maybe my gcc > > will generate similar code to his and the function offset is enough > > clue. > > So the code section says the faulting instruction is: > > f3 a5 > > followed by: > > 48 89 c7 85 50 ff ff > > or so. > > My compiled code is 'different', the function is shorter, but there's a > f3 a5 somewhere not too far short of +d7 at +a8. I have (objdump -SD): > > 35a8: f3 a5 rep movsl %ds:(%rsi),%es:(%rdi) > > for_each_cpu_and(i, sched_group_cpus(group), env->cpus) { > unsigned long capacity, capacity_factor, wl; > enum fbq_type rt; > > rq = cpu_rq(i); > 35aa: 48 c7 c1 00 00 00 00 mov $0x0,%rcx > > And that's the only part that could possibly match. > > That looks like the start of find_busiest_queue(). I'm not entirely sure > what the rep movsl is operating on, lemme try and figure that out. Ah, this appears to be load_balance()'s: cpumask_copy(cpus, cpu_active_mask); Which totally doesn't make sense, both src and dst are static storage. Dst is the most interesting since its per-cpu storage, but still. No way either of those should generate a #GP. Puzzled. -- 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/