From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946167AbXBCBF0 (ORCPT ); Fri, 2 Feb 2007 20:05:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1946203AbXBCBF0 (ORCPT ); Fri, 2 Feb 2007 20:05:26 -0500 Received: from smtp.osdl.org ([65.172.181.24]:47429 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1946167AbXBCBFZ (ORCPT ); Fri, 2 Feb 2007 20:05:25 -0500 Date: Fri, 2 Feb 2007 17:05:00 -0800 From: Andrew Morton To: ebiederm@xmission.com (Eric W. Biederman) Cc: , "Lu, Yinghai" , "Luigi Genoni" , Ingo Molnar , Natalie Protasevich , Andi Kleen Subject: Re: [PATCH 2/2] x86_64 irq: Handle irqs pending in IRR during irq migration. Message-Id: <20070202170500.57b6c3a3.akpm@linux-foundation.org> In-Reply-To: References: <200701221116.13154.luigi.genoni@pirelli.com> <200702021848.55921.luigi.genoni@pirelli.com> <200702021905.39922.luigi.genoni@pirelli.com> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.6; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 02 Feb 2007 17:35:31 -0700 ebiederm@xmission.com (Eric W. Biederman) wrote: > When making the interrupt vectors per cpu I failed to handle a case > during irq migration. If the same interrupt comes in while we are > servicing the irq but before we migrate it the pending bit in the > local apic IRR register will be set for that irq. > > After migrating the irq to another cpu and or vector the data > structures will no longer be setup to handle this pending irq. Then as > soon as we return from servicing the irq we just migrated we will get > a nasty: "No irq handler for vector" message. > > Since we do not disable irqs for edge triggered interrupts except > in the smallest possible window during migration I cannot avoid > migrating an irq in the unlikely event that it becomes pending. > This is because by the time the irq could no longer become pending > I have already updated all of my data structures. > > Therefore this patch introduces an intermediate state that > exists soley on the cpu where we are handling the irq during > migration. The irq number is changed to negative in the > vector_irq data structure. > > Once the migration operation is complete we know we will receive > no more interrupts on this vector so the irq pending state for > this irq will no longer be updated. If the irq is not pending and > we are in the intermediate state we immediately free the vector, > otherwise in we free the vector in do_IRQ when the pending irq > arrives. So is this a for-2.6.20 thing? The bug was present in 2.6.19, so I assume it doesn't affect many people?