Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946211AbXBCCBZ (ORCPT ); Fri, 2 Feb 2007 21:01:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1946213AbXBCCBY (ORCPT ); Fri, 2 Feb 2007 21:01:24 -0500 Received: from smtp.osdl.org ([65.172.181.24]:51188 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1946211AbXBCCBY (ORCPT ); Fri, 2 Feb 2007 21:01:24 -0500 Date: Fri, 2 Feb 2007 18:01:03 -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: <20070202180103.cf1e4217.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> <20070202170500.57b6c3a3.akpm@linux-foundation.org> 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 Content-Length: 1697 Lines: 40 On Fri, 02 Feb 2007 18:39:15 -0700 ebiederm@xmission.com (Eric W. Biederman) wrote: > Andrew Morton writes: > > > 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? > > If it's not to late, and this patch isn't too scary. > > It's a really rare set of circumstances that trigger it, but the > possibility of being hit is pretty widespread, anything with > more than one cpu, and more then one irq could see this. > > The easiest way to trigger this is to have two level triggered irqs on > two different cpus using the same vector. In that case if one acks > it's irq while the other irq is migrating to a different cpu 2.6.19 > get completely confused and stop handling interrupts properly. > > With my previous bug fix (not to drop the ack when we are confused) > the machine will stay up, and that is obviously correct and can't > affect anything else so is probably a candidate for the stable tree. > > With this fix everything just works. > > I don't know how often a legitimate case of the exact same irq > going off twice in a row is, but that is a possibility as well > especially with edge triggered interrupts. > > Setting up the test scenario was a pain, but by extremely limiting > my choice of vectors I was able to confirm I survived several hundred > of these events with in a couple of minutes no problem. > OK, thanks. Let's await Andi's feedback. - 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/