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From: Ville Herva <>
To: Andi Kleen <>
Cc: Mikael Pettersson <>,
Subject: Re: [PATCH] NMI watchdog documentation
Date: Tue, 29 Jul 2003 20:53:19 +0300	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Tue, Jul 29, 2003 at 06:06:30PM +0200, you [Andi Kleen] wrote:
> > Andi, you have the numbers mixed up. mode 1 is I/O-APIC, mode 2 is local APIC,
> > and x86-64 defaults nmi_watchdog to I/O-APIC mode.
> > Now, is it the I/O-APIC or local APIC watchdog that doesn't work in x86-64?
> Right, 1 and 2 need to be exchanged. Anyways local apic mode does not seem
> to work, the kernel always reportss "NMI stuck" at bootup.
> IO APIC mode for is default.
> I have not tested if it works with a 32bit kernel on an Opteron box.

Ok, I'll send the following to Linus and Marcelo unless you object.

-- v --

--- /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=1 does not work on x86-64.
+Using NMI watchdog (in mode=2) needs the first performance register, so you
+can't use it for other purposes (such as high precision performance
 To actually enable the NMI watchdog, use the 'nmi_watchdog=N' boot
 parameter.  Eg. the relevant lilo.conf entry:

  reply	other threads:[~2003-07-29 17:58 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-07-29 10:37 [PATCH] NMI watchdog documentation Mikael Pettersson
2003-07-29 16:06 ` Andi Kleen
2003-07-29 17:53   ` Ville Herva [this message]
  -- strict thread matches above, loose matches on Subject: below --
2003-07-31 21:25 Mikael Pettersson
2003-07-30 22:53 Mikael Pettersson
2003-07-31  5:44 ` Ville Herva
2003-07-30 19:20 Mikael Pettersson
2003-07-30 19:40 ` Ville Herva
2003-07-30 19:18 Mikael Pettersson
2003-07-23 17:43 Ville Herva
2003-07-28 17:53 ` Andi Kleen
2003-07-28 19:21   ` Ville Herva

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