Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753090AbaKRCKQ (ORCPT ); Mon, 17 Nov 2014 21:10:16 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46799 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752917AbaKRCKJ (ORCPT ); Mon, 17 Nov 2014 21:10:09 -0500 Date: Mon, 17 Nov 2014 21:09:59 -0500 From: Dave Jones To: Linus Torvalds Cc: Linux Kernel , the arch/x86 maintainers Subject: Re: frequent lockups in 3.18rc4 Message-ID: <20141118020959.GA2091@redhat.com> Mail-Followup-To: Dave Jones , Linus Torvalds , Linux Kernel , the arch/x86 maintainers References: <20141114213124.GB3344@redhat.com> <20141115213405.GA31971@redhat.com> <20141116014006.GA5016@redhat.com> <20141117170359.GA1382@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 17, 2014 at 11:59:34AM -0800, Linus Torvalds wrote: > On Mon, Nov 17, 2014 at 9:03 AM, Dave Jones wrote: > > > > It could a completely different cause for lockup, but seeing this now > > has me wondering if perhaps it's something unrelated to the kernel. > > I have recollection of running late .17rc's for days without incident, > > and I'm pretty sure .17 was ok too. But a few weeks ago I did upgrade > > that test box to the Fedora 21 beta. Which means I have a new gcc. > > I'm not sure I really trust 4.9.1 yet, so maybe I'll see if I can > > get 4.8 back on there and see if that's any better. > > I'm not sure if I should be relieved or horrified. > > Horrified, I think. > > It really would be a wonderful thing to have some kind of "compiler > bisection" with mixed object files to see exactly which file it > miscompiles (and by "miscompiles" it might just be a kernel bug where > we are missing a barrier or something, and older gcc's just happened > to not show it - so it could still easily be a kernel problem). After wasting countless hours rolling back to Fedora 20 and gcc 4.8.1, I saw the exact same trace on 3.17, so now I don't know what to think. So it's great that it's not a regression vs .17, but otoh, who knows how far back this goes. This looks like a nightmarish bisect case, and I've no idea why it's now happening so often. I'll give Don's softlockup_all_cpu_backtrace=1 idea a try on 3.18rc5 and see if that shines any more light on this. Deeply puzzling. Dave -- 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/