From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758326AbYFBKj6 (ORCPT ); Mon, 2 Jun 2008 06:39:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751192AbYFBKjs (ORCPT ); Mon, 2 Jun 2008 06:39:48 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:55212 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752269AbYFBKjr (ORCPT ); Mon, 2 Jun 2008 06:39:47 -0400 Date: Mon, 2 Jun 2008 12:39:31 +0200 From: Ingo Molnar To: Jason Wessel Cc: lkml , Andrew Morton , a.p.zijlstra@chello.nl Subject: Re: [PATCH] softlockup: fix NMI hangs due to lock race - 2.6.26-rc regression Message-ID: <20080602103931.GA898@elte.hu> References: <483C4391.8040002@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <483C4391.8040002@windriver.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Jason Wessel wrote: > The touch_nmi_watchdog() routine on x86 ultimately calls > touch_softlockup_watchdog(). The problem is that to touch the > softlockup watchdog, the cpu_clock code has to be called which could > involve multiple cpu locks and can lead to a hard hang if one of the > locks is held by a processor that is not going to return anytime soon > (such as could be the case with kgdb or perhaps even with some other > kind of exception). > > This patch causes the public version of the > touch_softlockup_watchdog() to defer the cpu clock access to a later > point. applied to tip/core/softlockup and cherry-picked it into tip/core/urgent as well for v2.6.26 merge. Thanks, Ingo