Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751700AbbEXTdm (ORCPT ); Sun, 24 May 2015 15:33:42 -0400 Received: from mail-la0-f50.google.com ([209.85.215.50]:34312 "EHLO mail-la0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751424AbbEXTdj (ORCPT ); Sun, 24 May 2015 15:33:39 -0400 Date: Sun, 24 May 2015 21:34:04 +0200 From: Christoffer Dall To: linux-mm@kvack.org, ebru.akagunduz@gmail.com Cc: 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: [BUG] Read-Only THP causes stalls (commit 10359213d) Message-ID: <20150524193404.GD16910@cbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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: 1532 Lines: 36 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. 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/