1 files changed, 3 insertions, 2 deletions

diff --git a/arch/x86/kernel/apic/nmi.c b/arch/x86/kernel/apic/nmi.c
index d6bd62407152..ce4fbfa315a1 100644
--- a/arch/x86/kernel/apic/nmi.c
+++ b/arch/x86/kernel/apic/nmi.c
@@ -138,7 +138,7 @@ int __init check_nmi_watchdog(void)
         if (!prev_nmi_count)
                 goto error;
 
-        alloc_cpumask_var(&backtrace_mask, GFP_KERNEL);
+        alloc_cpumask_var(&backtrace_mask, GFP_KERNEL|__GFP_ZERO);
         printk(KERN_INFO "Testing NMI watchdog ... ");
 
 #ifdef CONFIG_SMP
@@ -414,7 +414,8 @@ nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
                 touched = 1;
         }
 
-        if (cpumask_test_cpu(cpu, backtrace_mask)) {
+        /* We can be called before check_nmi_watchdog, hence NULL check. */
+        if (backtrace_mask != NULL && cpumask_test_cpu(cpu, backtrace_mask)) {
                 static DEFINE_SPINLOCK(lock);   /* Serialise the printks */
 
                 spin_lock(&lock);