1 files changed, 37 insertions, 2 deletions

diff --git a/arch/i386/kernel/nmi.c b/arch/i386/kernel/nmi.c
index 72515b8a1b12..d661703ac1cb 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 */