From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757963Ab2B2SDv (ORCPT ); Wed, 29 Feb 2012 13:03:51 -0500 Received: from out02.mta.xmission.com ([166.70.13.232]:52348 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756745Ab2B2SDu (ORCPT ); Wed, 29 Feb 2012 13:03:50 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: Keith Chew Cc: linux-kernel References: Date: Wed, 29 Feb 2012 10:07:00 -0800 In-Reply-To: (Keith Chew's message of "Sat, 18 Feb 2012 11:54:25 +1300") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-XM-SPF: eid=;;;mid=;;;hst=in02.mta.xmission.com;;;ip=98.207.153.68;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18M6XjhTaj71x2uTI5EPNPeZvuTjsxTbEQ= X-SA-Exim-Connect-IP: 98.207.153.68 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.4933] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa01 1397; Body=1 Fuz1=1 Fuz2=1] * 0.4 UNTRUSTED_Relay Comes from a non-trusted relay X-Spam-DCC: XMission; sa01 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: *;Keith Chew X-Spam-Relay-Country: ** Subject: Re: Hang on "echo b > /proc/sysrq-trigger" X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Fri, 06 Aug 2010 16:31:04 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Keith Chew writes: > Hi > > To test the reliability of a hardware, I have a script which reboots a > machine every 15 minutes after boot up. This machine has a dual video > output, VGA and DVI-D, both driven via an intel GM45 chipset (I am > using kernel 2.6.39.24 kernel intel drivers). > > Some interesting results (which can be reproduced consistently): > "echo b > /proc/sysrq-trigger" via DVI-D - after 2-3 days, it hangs > (freezes) before reboot (dmesg only shows "Resetting...", nothing My blind guess would be that it is the BIOS on the machine that is hung. > after that, no panic, stack trace, etc) > "echo b > /proc/sysrq-trigger" via VGA - runs > 1 week > "reboot -fn" via VGA or DVI-D - runs > 1 week > "reboot" via VGA or DVI-D - runs > 1 week > > I suspect that the intel graphics driver is not happy with the "echo b >> /proc/sysrq-trigger" when it is still running. > > I would like to make the "echo b" successfully reboot the machine, but > this would appear to be a hardware bug? Is there anything that can be > done in the kernel to make the "echo b" successfully work 100%? echo b > /proc/sysrq-trigger triggers the emergency_restart path which tries but skips some steps so that it has a reasonable chance of working when the kernel is wedged, it looks like some of those steps it skips are needed on your hardware. Eric