From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750713AbWFBLyA (ORCPT ); Fri, 2 Jun 2006 07:54:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751137AbWFBLyA (ORCPT ); Fri, 2 Jun 2006 07:54:00 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:45215 "EHLO ebiederm.dsl.xmission.com") by vger.kernel.org with ESMTP id S1750713AbWFBLx7 (ORCPT ); Fri, 2 Jun 2006 07:53:59 -0400 To: Preben Traerup Cc: "Akiyama, Nobuyuki" , fastboot@lists.osdl.org, linux-kernel@vger.kernel.org, Vivek Goyal Subject: Re: [Fastboot] [RFC][PATCH] Add missing notifier before crashing References: <20060530183359.a8d5d736.akiyama.nobuyuk@jp.fujitsu.com> <20060530145658.GC6536@in.ibm.com> <20060531182045.9db2fac9.akiyama.nobuyuk@jp.fujitsu.com> <20060531154322.GA8475@in.ibm.com> <20060601213730.dc9f1ec4.akiyama.nobuyuk@jp.fujitsu.com> <20060601151605.GA7380@in.ibm.com> <20060602141301.cdecf0e1.akiyama.nobuyuk@jp.fujitsu.com> <44800E1A.1080306@ericsson.com> From: ebiederm@xmission.com (Eric W. Biederman) Date: Fri, 02 Jun 2006 05:52:32 -0600 In-Reply-To: <44800E1A.1080306@ericsson.com> (Preben Traerup's message of "Fri, 02 Jun 2006 12:08:26 +0200") Message-ID: User-Agent: Gnus/5.1007 (Gnus v5.10.7) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Preben Traerup writes: > Since I'm one of the people who very much would like best of both worlds, > I do belive Vivek Goyal's concern about the reliability of kdump must be > adressed properly. > > I do belive the crash notifier should at least be a list of its own. > Attaching element to the list proves your are kdump aware - in theory > > However: > > Conceptually I do not like the princip of implementing crash notifier > as a list simply because for all (our) practical usage there will only > be one element attached to the list anyway. > > And as I belive crash notifiers only will be used by a very limited > number of users, I suggested in another mail that a simple > > if (function pointer) > call functon > > approach to be used for this special case to keep things very simple. I am completely against crash notifiers. The code crash_kexec switches to is what is notified and it can do whatever it likes. The premise is that the kernel does not work. Therefore we cannot safely notify kernel code. We do the very minimal to get out of the kernel, and it is my opinion we still do to much. The crash_kexec entry point is not about taking crash dumps. It is about implementing policy when the kernel panics. Generally the policy we want is a crash dump but the mechanism is general purpose and not limited to that. You can put anything you want for crash_kexec to execute. If the problem is strictly limited to hardware failure and software can cope with that then don't panic the kernel and execute an orderly transition. If software cannot cope, and must panic the kernel it clearly cannot do something sensible. Eric