[PATCH] i386 prepare nmi watchdog for dynticks

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>
Cc: Andi Kleen <ak@suse.de>
Cc: Zachary Amsden <zach@vmware.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Rohit Seth <rohitseth@google.com>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/i386/kernel/nmi.c b/arch/i386/kernel/nmi.c
index 5d8a07c202817ef2013ea12430ca3fd331eaccb7..821df34d2b3a3a1b8a71ada0a77b64229e0f0200 100644 (file)
--- a/arch/i386/kernel/nmi.c
+++ b/arch/i386/kernel/nmi.c
@@ -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>
@@ -973,9 +974,13 @@ __kprobes int nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
                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 ...