1 files changed, 21 insertions, 20 deletions

diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index cefd6942f0e9..72ec29e1ae06 100644
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -17,19 +17,31 @@
 #include <linux/nmi.h>
 #include <linux/module.h>
 
-/* For reliability, we're prepared to waste bits here. */
-static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
-
+#ifdef CONFIG_HARDLOCKUP_DETECTOR
 u64 hw_nmi_get_sample_period(void)
 {
         return (u64)(cpu_khz) * 1000 * 60;
 }
+#endif
+
+#ifdef arch_trigger_all_cpu_backtrace
+/* For reliability, we're prepared to waste bits here. */
+static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
+
+/* "in progress" flag of arch_trigger_all_cpu_backtrace */
+static unsigned long backtrace_flag;
 
-#ifdef ARCH_HAS_NMI_WATCHDOG
 void arch_trigger_all_cpu_backtrace(void)
 {
         int i;
 
+        if (test_and_set_bit(0, &backtrace_flag))
+                /*
+                 * If there is already a trigger_all_cpu_backtrace() in progress
+                 * (backtrace_flag == 1), don't output double cpu dump infos.
+                 */
+                return;
+
         cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask);
 
         printk(KERN_INFO "sending NMI to all CPUs:\n");
@@ -41,6 +53,9 @@ void arch_trigger_all_cpu_backtrace(void)
                         break;
                 mdelay(1);
         }
+
+        clear_bit(0, &backtrace_flag);
+        smp_mb__after_clear_bit();
 }
 
 static int __kprobes
@@ -49,7 +64,7 @@ arch_trigger_all_cpu_backtrace_handler(struct notifier_block *self,
 {
         struct die_args *args = __args;
         struct pt_regs *regs;
-        int cpu = smp_processor_id();
+        int cpu;
 
         switch (cmd) {
         case DIE_NMI:
@@ -61,6 +76,7 @@ arch_trigger_all_cpu_backtrace_handler(struct notifier_block *self,
         }
 
         regs = args->regs;
+        cpu = smp_processor_id();
 
         if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
                 static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED;
@@ -90,18 +106,3 @@ static int __init register_trigger_all_cpu_backtrace(void)
 }
 early_initcall(register_trigger_all_cpu_backtrace);
 #endif
-
-/* STUB calls to mimic old nmi_watchdog behaviour */
-#if defined(CONFIG_X86_LOCAL_APIC)
-unsigned int nmi_watchdog = NMI_NONE;
-EXPORT_SYMBOL(nmi_watchdog);
-void acpi_nmi_enable(void) { return; }
-void acpi_nmi_disable(void) { return; }
-#endif
-atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */
-EXPORT_SYMBOL(nmi_active);
-int unknown_nmi_panic;
-void cpu_nmi_set_wd_enabled(void) { return; }
-void stop_apic_nmi_watchdog(void *unused) { return; }
-void setup_apic_nmi_watchdog(void *unused) { return; }
-int __init check_nmi_watchdog(void) { return 0; }