From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932233AbWFSH33 (ORCPT ); Mon, 19 Jun 2006 03:29:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932219AbWFSH33 (ORCPT ); Mon, 19 Jun 2006 03:29:29 -0400 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:33193 "EHLO fgwmail7.fujitsu.co.jp") by vger.kernel.org with ESMTP id S932221AbWFSH32 (ORCPT ); Mon, 19 Jun 2006 03:29:28 -0400 Date: Mon, 19 Jun 2006 16:30:53 +0900 From: "Akiyama, Nobuyuki" To: ebiederm@xmission.com (Eric W. Biederman) Cc: fastboot@lists.osdl.org, linux-kernel@vger.kernel.org Subject: Re: [Fastboot] [PATCH] kdump: add a missing notifier before crashing Message-Id: <20060619163053.f0f10a5e.akiyama.nobuyuk@jp.fujitsu.com> In-Reply-To: References: <20060615201621.6e67d149.akiyama.nobuyuk@jp.fujitsu.com> <20060616211555.1e5c4af0.akiyama.nobuyuk@jp.fujitsu.com> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.6.10; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 16 Jun 2006 10:37:05 -0600 ebiederm@xmission.com (Eric W. Biederman) wrote: > > The processing of the notifier is to make a SCSI adaptor power off to > > stop writing in the shared disk completely and then notify to standby-node. > > The kernel has called panic no new SCSI operations were execute. > I'm not saying don't notify your standby-node As you say, the kernel does not do anything about SCSI operations. But many SCSI adaptors flush their cache after a few seconds pass after a SCSI write command is invoked, especially RAID cards. To completely stop writing immediately, we should make the adaptor power off. > Please walk me through a real world kernel failure, and show me how > your millisecond requirement is met. > > In the example please answer: > - What causes the kernel to call panic? > - From the real failure to the kernel calling panic how long > does it take? For instance, if a file system inconsistency is detected, it takes few time until invoking panic. I have seen various kernel failure so far and these will unfortunately occur. > - What actions does the notifier take to tell the other kernel > it is dead. The operation is only writing to BMC a few times to use IPMI interface. That operation using outb is very simple. > - Why do we think the kernel taking that action will be reliable? I agree the notifier may spoil reliability as compared with doing nothing. It depends on quality of the notifier processing. But I think the one is needed because it is more effective. > - From the point where we call panic() how long does it take until > the kdump kernel is active? On my box it takes about one second or so, but on a actual enterprise system which have many disks(hundreds or more) it becomes more. Thanks, -- Akiyama, Nobuyuki