[PATCH for review] [23/145] i386: Enable NMI watchdog by default

From: Andi Kleen
Date: Thu Aug 10 2006 - 16:36:05 EST


I've had good experiences with having this on by default on x86-64.
It turns nasty hangs into easier to debug oopses.

Enable the local APIC wdog by default for systems newer than 2004.

This comes from a strange compromise: according to arjan the reason
it was off by default was some old IBM systems that corrupted
registered when NMI happened in SMI. Can't remember more specific,
but >= 2004 should avoid these. It's probably overly broad
because most older systems should be ok (and the really old systems
won't be supported by the local apic watchdog anyways)

Signed-off-by: Andi Kleen <ak@xxxxxxx>

arch/i386/kernel/nmi.c | 9 +++++++++
1 files changed, 9 insertions(+)

Index: linux/arch/i386/kernel/nmi.c
--- linux.orig/arch/i386/kernel/nmi.c
+++ linux/arch/i386/kernel/nmi.c
@@ -21,6 +21,7 @@
#include <linux/sysdev.h>
#include <linux/sysctl.h>
#include <linux/percpu.h>
+#include <linux/dmi.h>

#include <asm/smp.h>
#include <asm/nmi.h>
@@ -204,6 +205,14 @@ static int __init check_nmi_watchdog(voi
unsigned int *prev_nmi_count;
int cpu;

+ /* Enable NMI watchdog for newer systems.
+ Actually it should be safe for most systems before 2004 too except
+ for some IBM systems that corrupt registers when NMI happens
+ during SMM. Unfortunately we don't have more exact information
+ on these and use this coarse check. */
+ if (nmi_watchdog == NMI_DEFAULT && dmi_get_year(DMI_BIOS_DATE) >= 2004)
+ nmi_watchdog = NMI_LOCAL_APIC;
if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DEFAULT))
return 0;

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/