From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S274874AbTGaVZ2 (ORCPT ); Thu, 31 Jul 2003 17:25:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S274876AbTGaVZ2 (ORCPT ); Thu, 31 Jul 2003 17:25:28 -0400 Received: from meryl.it.uu.se ([130.238.12.42]:45218 "EHLO meryl.it.uu.se") by vger.kernel.org with ESMTP id S274874AbTGaVZN (ORCPT ); Thu, 31 Jul 2003 17:25:13 -0400 Date: Thu, 31 Jul 2003 23:25:09 +0200 (MEST) Message-Id: <200307312125.h6VLP9G6022368@harpo.it.uu.se> From: Mikael Pettersson To: vherva@niksula.hut.fi Subject: Re: [PATCH] NMI watchdog documentation Cc: ak@suse.de, linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 31 Jul 2003 08:44:48 +0300, Ville Herva wrote: >Uuh, sorry. Is the one below ok by you for submission to Linus and Marcelo? > > >-- v -- > >v@iki.fi > >--- linux/Documentation/nmi_watchdog.txt Sun Jul 27 19:58:26 2003 >+++ linux~/Documentation/nmi_watchdog.txt Tue Jul 29 21:08:01 2003 >@@ -1,9 +1,11 @@ > >-Is your ix86 system locking up unpredictably? No keyboard activity, just >+[NMI watchdog is available for x86 and x86-64 architectures] >+ >+Is your system locking up unpredictably? No keyboard activity, just > a frustrating complete hard lockup? Do you want to help us debugging > such lockups? If all yes then this document is definitely for you. > >-On Intel and similar ix86 type hardware there is a feature that enables >+On many x86/x86-64 type hardware there is a feature that enables > us to generate 'watchdog NMI interrupts'. (NMI: Non Maskable Interrupt > which get executed even if the system is otherwise locked up hard). > This can be used to debug hard kernel lockups. By executing periodic >@@ -20,6 +22,15 @@ > kernel debugging options, such as Kernel Stack Meter or Kernel Tracer, > may implicitly disable the NMI watchdog.] > >+For x86-64, the needed APIC is always compiled in, and the NMI watchdog is >+always enabled with I/O-APIC mode (nmi_watchdog=1). Currently, local APIC >+mode (nmi_watchdog=2) does not work on x86-64. >+ >+Using local APIC (nmi_watchdog=2) needs the first performance register, so >+you can't use it for other purposes (such as high precision performance >+profiling.) However, at least oprofile and the perfctr driver disable the >+local APIC NMI watchdog automatically. >+ > To actually enable the NMI watchdog, use the 'nmi_watchdog=N' boot > parameter. Eg. the relevant lilo.conf entry: Looks Ok to me. /Mikael