Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S270435AbTG1TVz (ORCPT ); Mon, 28 Jul 2003 15:21:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S270448AbTG1TVz (ORCPT ); Mon, 28 Jul 2003 15:21:55 -0400 Received: from twilight.cs.hut.fi ([130.233.40.5]:48942 "EHLO twilight.cs.hut.fi") by vger.kernel.org with ESMTP id S270435AbTG1TVx (ORCPT ); Mon, 28 Jul 2003 15:21:53 -0400 Date: Mon, 28 Jul 2003 22:21:42 +0300 From: Ville Herva To: Andi Kleen Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] NMI watchdog documentation Message-ID: <20030728192142.GR83336@niksula.cs.hut.fi> Mail-Followup-To: Ville Herva , Andi Kleen , linux-kernel@vger.kernel.org References: <20030723174325.GL150921@niksula.cs.hut.fi> <20030728195342.02913727.ak@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030728195342.02913727.ak@suse.de> User-Agent: Mutt/1.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2231 Lines: 53 On Mon, Jul 28, 2003 at 07:53:42PM +0200, you [Andi Kleen] wrote: > > x86-64 is the same, except APIC is always compiled in and the nmi watchdog is > always enabled with perfctr mode. mode=2 seems to also not work correctly currently. > > However one caveat (even for i386): when you use perfctr mode 1 you lose the first > performance register which you may need for other things. Thanks. So, is something like the following ok by you (patch is relative to -test2 nmi-watchdog.txt)? If it is, I'll send it to Linus and Marcelo. -- v -- v@iki.fi --- /usr/src/linux/Documentation/nmi_watchdog.txt Mon Jul 28 22:10:18 2003 +++ /usr/src/linux~/Documentation/nmi_watchdog.txt Mon Jul 28 22:18:10 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 +22,13 @@ kernel debugging options such as Kernel Stack Meter or Kernel Tracer may implicitly disable NMI watchdog.] +For x86-64, the needed APIC is always compiled in, and the NMI watchdog is +always enabled with perfctr mode. Currently, mode=2 does not work on x86-64. + +Using NMI watchdog (in mode=1) needs the first performance register, so you +can't use it for other purposes (such as high precision performance +profiling.) + To actually enable the NMI watchdog, use the 'nmi_watchdog=N' boot parameter. Eg. the relevant lilo.conf entry: - 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/