diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index ee886fe10ef4eb8515ae1d2431c0ce8ad3e8dd89..5fdc0950da1db2f9f9a77b7cb1e5d0286d448d2b 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -97,12 +97,12 @@ static DEFINE_PER_CPU(struct task_struct *, idle_thread_array);
  */
 static DEFINE_MUTEX(x86_cpu_hotplug_driver_mutex);
 
-void cpu_hotplug_driver_lock()
+void cpu_hotplug_driver_lock(void)
 {
         mutex_lock(&x86_cpu_hotplug_driver_mutex);
 }
 
-void cpu_hotplug_driver_unlock()
+void cpu_hotplug_driver_unlock(void)
 {
         mutex_unlock(&x86_cpu_hotplug_driver_mutex);
 }