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    Subject[patch 17/19] dynticks: Fix nmi watchdog
    From: Thomas Gleixner <tglx@linutronix.de>

    The NMI watchdog implementation assumes that the local APIC timer
    interrupt is happening. This assumption is not longer true when
    high resolution timers and dynamic ticks come into play, as they
    may switch off the local APIC timer completely. Take the PIT/HPET
    interrupts into account too, to avoid false positives.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>

    Index: linux-2.6.19-rc5-mm1/arch/i386/kernel/nmi.c
    ===================================================================
    --- linux-2.6.19-rc5-mm1.orig/arch/i386/kernel/nmi.c 2006-11-09 17:47:58.000000000 +0100
    +++ linux-2.6.19-rc5-mm1/arch/i386/kernel/nmi.c 2006-11-09 20:52:29.000000000 +0100
    @@ -23,6 +23,7 @@
    #include <linux/dmi.h>
    #include <linux/kprobes.h>
    #include <linux/cpumask.h>
    +#include <linux/kernel_stat.h>

    #include <asm/smp.h>
    #include <asm/nmi.h>
    @@ -920,9 +921,13 @@ __kprobes int nmi_watchdog_tick(struct p
    cpu_clear(cpu, backtrace_mask);
    }

    - sum = per_cpu(irq_stat, cpu).apic_timer_irqs;
    + /*
    + * Take the local apic timer and PIT/HPET into account. We don't
    + * know which one is active, when we have highres/dyntick on
    + */
    + sum = per_cpu(irq_stat, cpu).apic_timer_irqs + kstat_irqs(0);

    - /* if the apic timer isn't firing, this cpu isn't doing much */
    + /* if the none of the timers isn't firing, this cpu isn't doing much */
    if (!touched && last_irq_sums[cpu] == sum) {
    /*
    * Ayiee, looks like this CPU is stuck ...
    --

    -
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