From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751381AbWFBQlH (ORCPT ); Fri, 2 Jun 2006 12:41:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751394AbWFBQlH (ORCPT ); Fri, 2 Jun 2006 12:41:07 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:24226 "EHLO ebiederm.dsl.xmission.com") by vger.kernel.org with ESMTP id S1751381AbWFBQlF (ORCPT ); Fri, 2 Jun 2006 12:41:05 -0400 To: vgoyal@in.ibm.com Cc: Preben Traerup , "Akiyama, Nobuyuki" , fastboot@lists.osdl.org, linux kernel mailing list Subject: Re: [Fastboot] [RFC][PATCH] Add missing notifier before crashing References: <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> <44803B1F.8070302@ericsson.com> <20060602153717.GC29610@in.ibm.com> From: ebiederm@xmission.com (Eric W. Biederman) Date: Fri, 02 Jun 2006 10:39:42 -0600 In-Reply-To: <20060602153717.GC29610@in.ibm.com> (Vivek Goyal's message of "Fri, 2 Jun 2006 11:37:17 -0400") 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 Vivek Goyal writes: > So basically the idea is that whatever one wants to do it should be done > in the next kernel, even notifications. But this might require some data > from the context of previous kernel, for example destination IP address etc. > So the associated data either needs to be passed to new kernel or it shall > have to be retrieved from permanent storage or something like that. Yes. Except when under tight time constraints this is clearly possible. When under time constraints things are more dicy. I expect that with a tuned kernel you can be back in user space in about 1 second. Detecting a failure is hard and slow. Unless the condition that triggers the panic is the initial source of the panic it is quite likely a time window less than 1 second has already elapsed. So I am certainly willing to discuss this but until I see a clear model where a new kernel will not meet the time constraints for some fairly fundamental reasons, and that a crash notifier will almost always meet those same time constraints, I can't imagine a persuasive case. The panic notifier itself is barely used and it seems to exist only because we didn't have a general purpose policy mechanism. Eric