Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752170AbbEYKTU (ORCPT ); Mon, 25 May 2015 06:19:20 -0400 Received: from mail-lb0-f179.google.com ([209.85.217.179]:35837 "EHLO mail-lb0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750859AbbEYKTT (ORCPT ); Mon, 25 May 2015 06:19:19 -0400 Date: Mon, 25 May 2015 12:19:44 +0200 From: Christoffer Dall To: "Kirill A. Shutemov" Cc: linux-mm@kvack.org, ebru.akagunduz@gmail.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, kirill.shutemov@linux.intel.com, riel@redhat.com, vbabka@suse.cz, zhangyanfei@cn.fujitsu.com, aarcange@redhat.com, Will Deacon , Andre Przywara , Marc Zyngier , linux-arm-kernel@lists.infradead.org Subject: Re: [BUG] Read-Only THP causes stalls (commit 10359213d) Message-ID: <20150525101944.GA14095@cbox> References: <20150524193404.GD16910@cbox> <20150525100515.GA8275@node.dhcp.inet.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150525100515.GA8275@node.dhcp.inet.fi> 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: 2511 Lines: 61 On Mon, May 25, 2015 at 01:05:15PM +0300, Kirill A. Shutemov wrote: > On Sun, May 24, 2015 at 09:34:04PM +0200, Christoffer Dall wrote: > > Hi all, > > > > I noticed a regression on my arm64 APM X-Gene system a couple > > of weeks back. I would occassionally see the system lock up and see RCU > > stalls during the caching phase of kernbench. I then wrote a small > > script that does nothing but cache the files > > (http://paste.ubuntu.com/11324767/) and ran that in a loop. On a known > > bad commit (v4.1-rc2), out of 25 boots, I never saw it get past 21 > > iterations of the loop. I have since tried to run a bisect from v3.19 to > > v4.0 using 100 iterations as my criteria for a good commit. > > > > This resulted in the following first bad commit: > > > > 10359213d05acf804558bda7cc9b8422a828d1cd > > (mm: incorporate read-only pages into transparent huge pages, 2015-02-11) > > > > Indeed, running the workload on v4.1-rc4 still produced the behavior, > > but reverting the above commit gets me through 100 iterations of the > > loop. > > > > I have not tried to reproduce on an x86 system. Turning on a bunch > > of kernel debugging features *seems* to hide the problem. My config for > > the XGene system is defconfig + CONFIG_BRIDGE and > > CONFIG_POWER_RESET_XGENE. > > > > Please let me know if I can help test patches or other things I can > > do to help. I'm afraid that by simply reading the patch I didn't see > > anything obviously wrong with it which would cause this behavior. > > I don't see the problem on x86. I'm wondering if we could have some weird combination of how the specific architecture works along with these patches... > > Some backtraces could help to track it down. > I don't really get backtraces as the sytem just locks up. But here are some of the RCU stalls as I've observed them on the console: http://paste.ubuntu.com/11014701/ http://paste.ubuntu.com/11023143/ http://paste.ubuntu.com/11023261/ Occasionally, I also get this error from the SATA system at the moment when I power off the device, but not sure if it is related: ata1: exception Emask 0x10 SAct 0x0 SErr 0x180000 action 0xe frozen ata1: irq_stat 0x00400000, PHY RDY changed ata1: SError: { 10B8B Dispar } Thanks, -Christoffer -- 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/