Messages in this thread Patch in this message | | | Date | Tue, 29 Jul 2003 20:53:19 +0300 | From | Ville Herva <> | Subject | Re: [PATCH] NMI watchdog documentation |
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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 --
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=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 +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/
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