From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753833AbXCTUCL (ORCPT ); Tue, 20 Mar 2007 16:02:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753888AbXCTUCK (ORCPT ); Tue, 20 Mar 2007 16:02:10 -0400 Received: from ozlabs.org ([203.10.76.45]:41318 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753833AbXCTUCJ (ORCPT ); Tue, 20 Mar 2007 16:02:09 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <17919.42767.233797.860230@cargo.ozlabs.ibm.com> Date: Tue, 20 Mar 2007 20:19:11 +1100 From: Paul Mackerras To: David Miller Cc: jesse.barnes@intel.com, zaitcev@redhat.com, jg@laptop.org, linux-kernel@vger.kernel.org Subject: Re: BSOD In-Reply-To: <20070319.130544.115907938.davem@davemloft.net> References: <20070319120807.af36ef5d.zaitcev@redhat.com> <20070319.123836.39155546.davem@davemloft.net> <200703191254.36373.jesse.barnes@intel.com> <20070319.130544.115907938.davem@davemloft.net> X-Mailer: VM 7.19 under Emacs 21.4.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org David Miller writes: > Mode setting is complex and it is not going to work exactly when you > need the kernel crash message the most. It's a matter of writing maybe a dozen MMIO registers on the ATI chips, for instance, with some delays. Provided we have interrupts disabled and udelay still works, there's not a lot of the kernel that we need to rely on to do that. > After debugging the kernel for 10+ years I can tell you one thing, for > a bad crash what's going to happen is you'll get the printk but that's > about all that will work at that point, and the kernel is going to > hang next. Sometimes you won't get the whole panic message, just > the beginning, even with the most simplistic printk implementation. > > You will not, I repeat, will not be able to mode switch or anything > non-trivial like that when the kernel is in this state. > > Mode switching on panic, just say no. :-) Anything is better than nothing. At the moment we get nothing if you are in X when the panic occurs, even for the nicest, most well-behaved panics. :) If we can change that to getting something sometimes, that's a win. Paul.