Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932870AbXHHOHa (ORCPT ); Wed, 8 Aug 2007 10:07:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754157AbXHHOHU (ORCPT ); Wed, 8 Aug 2007 10:07:20 -0400 Received: from mx1.redhat.com ([66.187.233.31]:51971 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751612AbXHHOHS (ORCPT ); Wed, 8 Aug 2007 10:07:18 -0400 Date: Wed, 8 Aug 2007 10:06:13 -0400 (EDT) From: Chip Coldwell To: Vivek Goyal cc: Martin Wilck , Haren Myneni , "kexec@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "Eric W. Biederman" Subject: Re: PATCH/RFC: [kdump] fix APIC shutdown sequence In-Reply-To: <20070808103603.GC13808@in.ibm.com> Message-ID: References: <46B73955.2080007@fujitsu-siemens.com> <20070807142928.GA18839@in.ibm.com> <46B8AECA.7050908@fujitsu-siemens.com> <20070808103603.GC13808@in.ibm.com> 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 Content-Length: 1310 Lines: 37 On Wed, 8 Aug 2007, Vivek Goyal wrote: > On Tue, Aug 07, 2007 at 07:41:30PM +0200, Martin Wilck wrote: > > > > Can you explain how, on the front side bus, the IO-APIC knows whether > > a CPU has accepted the INT message? There is no response > > to the INT message on the bus, except for the EOI which comes much later. > > I'm not saying that you're wrong, I just really don't understand this > > point. > > > > I don't know what is exactly hardware protocol. I am just going by > intel documentation. I think it's important to distinguish between the LAPIC receiving an interrupt and the CPU receiving an interrupt. The former could happen without the latter if the CPU has set the TPR above the priority of the interrupt received by the LAPIC. In that case, the interrupt is kept pending in the LAPIC and recorded in the IRR if I understand the Intel documentation correctly. So I think the scenario which leaves IRR set when the kdump kernel starts is possible. Chip -- Charles M. "Chip" Coldwell Senior Software Engineer Red Hat, Inc 978-392-2426 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/