From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751103AbWAYK2V (ORCPT ); Wed, 25 Jan 2006 05:28:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751107AbWAYK2V (ORCPT ); Wed, 25 Jan 2006 05:28:21 -0500 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:30116 "EHLO ebiederm.dsl.xmission.com") by vger.kernel.org with ESMTP id S1751103AbWAYK2U (ORCPT ); Wed, 25 Jan 2006 05:28:20 -0500 To: Fernando Luis Vazquez Cao Cc: Arjan van de Ven , Andrew Morton , Andi Kleen , ebiederm@xmission.com, vgoyal@in.ibm.com, linux-kernel@vger.kernel.org, fastboot@lists.osdl.org Subject: Re: [PATCH 1/5] stack overflow safe kdump (2.6.16-rc1-i386) - safe_smp_processor_id References: <1138171868.2370.62.camel@localhost.localdomain> <20060124231052.7c9fcbec.akpm@osdl.org> <200601250853.48193.ak@suse.de> <20060124235901.719aa375.akpm@osdl.org> <1138176439.3001.26.camel@laptopd505.fenrus.org> <1138179017.7159.13.camel@localhost.localdomain> From: ebiederm@xmission.com (Eric W. Biederman) Date: Wed, 25 Jan 2006 03:27:17 -0700 In-Reply-To: <1138179017.7159.13.camel@localhost.localdomain> (Fernando Luis Vazquez Cao's message of "Wed, 25 Jan 2006 17:50:17 +0900") 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 Fernando Luis Vazquez Cao writes: > On Wed, 2006-01-25 at 09:07 +0100, Arjan van de Ven wrote: >> On Tue, 2006-01-24 at 23:59 -0800, Andrew Morton wrote: >> > Andi Kleen wrote: >> > > >> > > On Wednesday 25 January 2006 08:10, Andrew Morton wrote: >> > > >> > > > It assumes that all x86 SMP machines have APICs. That's untrue of > Voyager. >> > > > I think we can probably live with this assumption - others would know >> > > > better than I. >> > > >> > > Early x86s didn't have APICs and they are still often disabled on not so >> > > old mobile CPUs. I don't think it's a good assumption to make for i386. >> > > >> > >> > But how many of those do SMP? >> >> even on SMP boxes you regularly need to (runtime) disable apics. Several >> boards out there just have busted apics, or at least when used with >> linux. "noapic" is one of the more frequent things distro support people >> tell customers over the phone.... > Checking whether ioapic_setup_disabled is set should suffice, right? > Does the patch below look good? Actually hard_smp_processor_id should only care about local apics. Disabling the io_apics should have no affect, on this code path. So I believe testing for io_apics being enabled is actively wrong. If the local apics are disabled the feature flag should be cleared, and we are uniprocessor anyway. Eric