From mboxrd@z Thu Jan 1 00:00:00 1970 From: u.kleine-koenig@pengutronix.de (Uwe =?iso-8859-1?Q?Kleine-K=F6nig?=) Date: Thu, 2 Jan 2014 11:14:55 +0100 Subject: v3.13-rc6+ regression (ARM board) In-Reply-To: References: <20131231104511.GA9688@1wt.eu> Message-ID: <20140102101455.GG10158@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hello Krzysztof, On Thu, Jan 02, 2014 at 11:02:44AM +0100, Krzysztof Ha?asa wrote: > >> There seems to be a regression in v3.13-rc6+ (up to current tip = > >> 71ce176ee6ed1735b9a1160a5704a915d13849b1). > >> > >> Board is Gateworks Cambria, CPU Intel IXP435 ARM big endian, gcc 4.7.3. > >> The board boots correctly and works (shell mostly, and SSHD) for about > >> 50 seconds. After 52-54 seconds, it frozes dead without any console > >> (UART) output. > >> > >> Bisecting shows 5e30025a319910695f5010dc0fb53a23299da14d as the first > >> bad commit. Interestingly it's a merge: > > Reverting 1ca7d67cf5d5a2aef26a8d9afd789006fa098347 on top of current tip > (9a0bb2966efbf30a71c128c3af63307d8b5f5fc0) fixes my issue. > > What now? > > 1ca7d67cf5d5a2aef26a8d9afd789006fa098347: > seqcount: Add lockdep functionality to seqcount/seqlock structures > > Currently seqlocks and seqcounts don't support lockdep. > > After running across a seqcount related deadlock in the timekeeping > code, I used a less-refined and more focused variant of this patch > to narrow down the cause of the issue. > > This is a first-pass attempt to properly enable lockdep functionality > on seqlocks and seqcounts. > > Since seqcounts are used in the vdso gettimeofday code, I've provided > non-lockdep accessors for those needs. > > I've also handled one case where there were nested seqlock writers > and there may be more edge cases. > > Comments and feedback would be appreciated! So it seems to be that 1ca7d67cf5d5a2aef26a8d9afd789006fa098347 doesn't like to be combined with some other commit from 5e30025a319910695f5010dc0fb53a23299da14d^2..5e30025a319910695f5010dc0fb53a23299da14d^. What you can do is: git bisect start 5e30025a319910695f5010dc0fb53a23299da14d^ b8a216269ec0ce2e961d32e6d640d7010b8a818e The bad commit is the tip of Linus' tree when he created the bad merge commit. The good one is the base of the merged tree. To check if a tree is good or bad do: git merge --no-commit 5e30025a319910695f5010dc0fb53a23299da14d^2 test test test git reset --hard git bisect good ... or ... git bisect bad That should find the commit that makes your board break in combination with 1ca7d67cf5d5a2aef26a8d9afd789006fa098347. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ | From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750942AbaABKPG (ORCPT ); Thu, 2 Jan 2014 05:15:06 -0500 Received: from metis.ext.pengutronix.de ([92.198.50.35]:44305 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750711AbaABKPF (ORCPT ); Thu, 2 Jan 2014 05:15:05 -0500 Date: Thu, 2 Jan 2014 11:14:55 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Krzysztof =?utf-8?Q?Ha=C5=82asa?= Cc: Willy Tarreau , John Stultz , Linus Torvalds , lkml , linux-arm-kernel@lists.infradead.org, Ingo Molnar Subject: Re: v3.13-rc6+ regression (ARM board) Message-ID: <20140102101455.GG10158@pengutronix.de> References: <20131231104511.GA9688@1wt.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-SA-Exim-Connect-IP: 2001:6f8:1178:2:21e:67ff:fe11:9c5c X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Krzysztof, On Thu, Jan 02, 2014 at 11:02:44AM +0100, Krzysztof Hałasa wrote: > >> There seems to be a regression in v3.13-rc6+ (up to current tip = > >> 71ce176ee6ed1735b9a1160a5704a915d13849b1). > >> > >> Board is Gateworks Cambria, CPU Intel IXP435 ARM big endian, gcc 4.7.3. > >> The board boots correctly and works (shell mostly, and SSHD) for about > >> 50 seconds. After 52-54 seconds, it frozes dead without any console > >> (UART) output. > >> > >> Bisecting shows 5e30025a319910695f5010dc0fb53a23299da14d as the first > >> bad commit. Interestingly it's a merge: > > Reverting 1ca7d67cf5d5a2aef26a8d9afd789006fa098347 on top of current tip > (9a0bb2966efbf30a71c128c3af63307d8b5f5fc0) fixes my issue. > > What now? > > 1ca7d67cf5d5a2aef26a8d9afd789006fa098347: > seqcount: Add lockdep functionality to seqcount/seqlock structures > > Currently seqlocks and seqcounts don't support lockdep. > > After running across a seqcount related deadlock in the timekeeping > code, I used a less-refined and more focused variant of this patch > to narrow down the cause of the issue. > > This is a first-pass attempt to properly enable lockdep functionality > on seqlocks and seqcounts. > > Since seqcounts are used in the vdso gettimeofday code, I've provided > non-lockdep accessors for those needs. > > I've also handled one case where there were nested seqlock writers > and there may be more edge cases. > > Comments and feedback would be appreciated! So it seems to be that 1ca7d67cf5d5a2aef26a8d9afd789006fa098347 doesn't like to be combined with some other commit from 5e30025a319910695f5010dc0fb53a23299da14d^2..5e30025a319910695f5010dc0fb53a23299da14d^. What you can do is: git bisect start 5e30025a319910695f5010dc0fb53a23299da14d^ b8a216269ec0ce2e961d32e6d640d7010b8a818e The bad commit is the tip of Linus' tree when he created the bad merge commit. The good one is the base of the merged tree. To check if a tree is good or bad do: git merge --no-commit 5e30025a319910695f5010dc0fb53a23299da14d^2 test test test git reset --hard git bisect good ... or ... git bisect bad That should find the commit that makes your board break in combination with 1ca7d67cf5d5a2aef26a8d9afd789006fa098347. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ |