[PATCH] x86: hpet: Fix HPET timer + NMI watchdog panic

[Yan, Zheng]

HPET doesn't use timer_interrupt() as interrupt handler now. So count of
HPET interrupt isn't recorded in per_cpu(irq_stat, cpu).irq0_irqs. This
confuses NMI watchdog when using HPET as tick device.

Signed-off-by: Yan, Zheng <zheng...@intel.com>

---
diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
index 55e4de6..cca94f2 100644
--- a/arch/x86/include/asm/hardirq.h
+++ b/arch/x86/include/asm/hardirq.h
@@ -12,6 +12,9 @@ typedef struct {
unsigned int apic_timer_irqs; /* arch dependent */
unsigned int irq_spurious_count;
#endif
+#ifdef CONFIG_HPET_TIMER
+ unsigned int hpet_timer_irqs;
+#endif
unsigned int x86_platform_ipis; /* arch dependent */
unsigned int apic_perf_irqs;
unsigned int apic_irq_work_irqs;
diff --git a/arch/x86/kernel/apic/nmi.c b/arch/x86/kernel/apic/nmi.c
index c90041c..cdb38d9 100644
--- a/arch/x86/kernel/apic/nmi.c
+++ b/arch/x86/kernel/apic/nmi.c
@@ -80,8 +80,15 @@ static inline int mce_in_progress(void)
*/
static inline unsigned int get_timer_irqs(int cpu)
{
- return per_cpu(irq_stat, cpu).apic_timer_irqs +
+ unsigned int irqs;
+#ifdef CONFIG_HPET_TIMER
+ irqs = per_cpu(irq_stat, cpu).hpet_timer_irqs;
+#else
+ irqs = 0;
+#endif
+ irqs += per_cpu(irq_stat, cpu).apic_timer_irqs +
per_cpu(irq_stat, cpu).irq0_irqs;
+ return irqs;
}

#ifdef CONFIG_SMP
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index 4ff5968..b536474c 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -517,6 +517,7 @@ static irqreturn_t hpet_interrupt_handler(int irq, void *data)
struct hpet_dev *dev = (struct hpet_dev *)data;
struct clock_event_device *hevt = &dev->evt;

+ inc_irq_stat(hpet_timer_irqs);
if (!hevt->event_handler) {
printk(KERN_INFO "Spurious HPET timer interrupt on HPET timer %d\n",
dev->num);
diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c
index fb5cc5e1..2098c56 100644
--- a/arch/x86/kernel/time.c
+++ b/arch/x86/kernel/time.c
@@ -56,7 +56,7 @@ unsigned long profile_pc(struct pt_regs *regs)
EXPORT_SYMBOL(profile_pc);

/*
- * Default timer interrupt handler for PIT/HPET
+ * Default timer interrupt handler for PIT
*/
static irqreturn_t timer_interrupt(int irq, void *dev_id)
{

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[Don Zickus]

On Wed, Dec 29, 2010 at 10:44:09AM +0800, Yan, Zheng wrote:
> HPET doesn't use timer_interrupt() as interrupt handler now. So count of
> HPET interrupt isn't recorded in per_cpu(irq_stat, cpu).irq0_irqs. This
> confuses NMI watchdog when using HPET as tick device.
>
> Signed-off-by: Yan, Zheng <zheng...@intel.com>

Not sure if this patch is needed because x86/kerne/apic/nmi.c will most
likely disappear in 2.6.38 (it is already in gone in linux-next). The new
nmi watchdog doesn't rely on HPET stats but instead uses a more generic
approach of a HRES timer.

Cheers,
Don