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-rw-r--r--arch/i386/kernel/nmi.c39
1 files changed, 37 insertions, 2 deletions
diff --git a/arch/i386/kernel/nmi.c b/arch/i386/kernel/nmi.c
index 72515b8a1b1..d661703ac1c 100644
--- a/arch/i386/kernel/nmi.c
+++ b/arch/i386/kernel/nmi.c
@@ -100,16 +100,44 @@ int nmi_active;
(P4_CCCR_OVF_PMI0|P4_CCCR_THRESHOLD(15)|P4_CCCR_COMPLEMENT| \
P4_CCCR_COMPARE|P4_CCCR_REQUIRED|P4_CCCR_ESCR_SELECT(4)|P4_CCCR_ENABLE)
+#ifdef CONFIG_SMP
+/* The performance counters used by NMI_LOCAL_APIC don't trigger when
+ * the CPU is idle. To make sure the NMI watchdog really ticks on all
+ * CPUs during the test make them busy.
+ */
+static __init void nmi_cpu_busy(void *data)
+{
+ volatile int *endflag = data;
+ local_irq_enable();
+ /* Intentionally don't use cpu_relax here. This is
+ to make sure that the performance counter really ticks,
+ even if there is a simulator or similar that catches the
+ pause instruction. On a real HT machine this is fine because
+ all other CPUs are busy with "useless" delay loops and don't
+ care if they get somewhat less cycles. */
+ while (*endflag == 0)
+ barrier();
+}
+#endif
+
static int __init check_nmi_watchdog(void)
{
- unsigned int prev_nmi_count[NR_CPUS];
+ volatile int endflag = 0;
+ unsigned int *prev_nmi_count;
int cpu;
if (nmi_watchdog == NMI_NONE)
return 0;
+ prev_nmi_count = kmalloc(NR_CPUS * sizeof(int), GFP_KERNEL);
+ if (!prev_nmi_count)
+ return -1;
+
printk(KERN_INFO "Testing NMI watchdog ... ");
+ if (nmi_watchdog == NMI_LOCAL_APIC)
+ smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);
+
for (cpu = 0; cpu < NR_CPUS; cpu++)
prev_nmi_count[cpu] = per_cpu(irq_stat, cpu).__nmi_count;
local_irq_enable();
@@ -123,12 +151,18 @@ static int __init check_nmi_watchdog(void)
continue;
#endif
if (nmi_count(cpu) - prev_nmi_count[cpu] <= 5) {
- printk("CPU#%d: NMI appears to be stuck!\n", cpu);
+ endflag = 1;
+ printk("CPU#%d: NMI appears to be stuck (%d->%d)!\n",
+ cpu,
+ prev_nmi_count[cpu],
+ nmi_count(cpu));
nmi_active = 0;
lapic_nmi_owner &= ~LAPIC_NMI_WATCHDOG;
+ kfree(prev_nmi_count);
return -1;
}
}
+ endflag = 1;
printk("OK.\n");
/* now that we know it works we can reduce NMI frequency to
@@ -136,6 +170,7 @@ static int __init check_nmi_watchdog(void)
if (nmi_watchdog == NMI_LOCAL_APIC)
nmi_hz = 1;
+ kfree(prev_nmi_count);
return 0;
}
/* This needs to happen later in boot so counters are working */