From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754484Ab0KJHuG (ORCPT ); Wed, 10 Nov 2010 02:50:06 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:40644 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752233Ab0KJHuE (ORCPT ); Wed, 10 Nov 2010 02:50:04 -0500 Date: Wed, 10 Nov 2010 08:49:41 +0100 From: Ingo Molnar To: Don Zickus Cc: fweisbec@gmail.com, Peter Zijlstra , LKML , akpm@linux-foundation.org, sergey.senozhatsky@gmail.com Subject: Re: [PATCH v3] watchdog: touch_nmi_watchdog should only touch local cpu not every one Message-ID: <20101110074941.GD29493@elte.hu> References: <1289240913-16677-1-git-send-email-dzickus@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1289240913-16677-1-git-send-email-dzickus@redhat.com> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -2.0 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 * Don Zickus wrote: > I ran into a scenario where while one cpu was stuck and should have panic'd > because of the NMI watchdog, it didn't. The reason was another cpu was spewing > stack dumps on to the console. Upon investigation, I noticed that when writing to > the console and also when dumping the stack, the watchdog is touched. > > This causes all the cpus to reset their NMI watchdog flags and the 'stuck' cpu > just spins forever. Hm, the flip side is that if a CPU is stuck spewing backtraces, we will now make all the other CPUs a lot more noisy - which might only 'lock up' because this CPU is stuck spewing oopses, right? Andrew, what would be your preference? Thanks, Ingo