1 files changed, 2 insertions, 1 deletions

diff --git a/arch/x86/kernel/apic/nmi.c b/arch/x86/kernel/apic/nmi.c
index d6bd62407152..2ba52f35a88c 100644
--- a/arch/x86/kernel/apic/nmi.c
+++ b/arch/x86/kernel/apic/nmi.c
@@ -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);