Re: [PATCH] NMI watchdog documentation
From: Mikael Pettersson (mikpe_at_csd.uu.se)
Date: 07/31/03
- Previous message: Benjamin Herrenschmidt: "Re: [linux-usb-devel] Re: OHCI problems with suspend/resume"
- Maybe in reply to: Ville Herva: "[PATCH] NMI watchdog documentation"
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Date: Thu, 31 Jul 2003 23:25:09 +0200 (MEST) To: vherva@niksula.hut.fi
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
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- Previous message: Benjamin Herrenschmidt: "Re: [linux-usb-devel] Re: OHCI problems with suspend/resume"
- Maybe in reply to: Ville Herva: "[PATCH] NMI watchdog documentation"
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