diff --git a/kernel/smpboot.h b/kernel/smpboot.h
index d88e771..7943bbb 100644
--- a/kernel/smpboot.h
+++ b/kernel/smpboot.h
@@ -1,6 +1,16 @@
 #ifndef SMPBOOT_H
 #define SMPBOOT_H
 
+struct task_struct;
+
 int smpboot_prepare(unsigned int cpu);
 
+#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
+struct task_struct *idle_thread_get(unsigned int cpu);
+void idle_thread_set_boot_cpu(void);
+#else
+static inline struct task_struct *idle_thread_get(unsigned int cpu) { return NULL; }
+static inline void idle_thread_set_boot_cpu(void) { }
+#endif
+
 #endif