diff --git a/include/asm-x86/mmu.h b/include/asm-x86/mmu.h
index 3f922c8..efa962c 100644
--- a/include/asm-x86/mmu.h
+++ b/include/asm-x86/mmu.h
@@ -20,4 +20,12 @@
 	void *vdso;
 } mm_context_t;
 
+#ifdef CONFIG_SMP
+void leave_mm(int cpu);
+#else
+static inline void leave_mm(int cpu)
+{
+}
+#endif
+
 #endif /* _ASM_X86_MMU_H */