Index: include/atomic.h
===================================================================
RCS file: /cvs/src/sys/arch/amd64/include/atomic.h,v
retrieving revision 1.18
diff -u -p -r1.18 atomic.h
--- include/atomic.h	17 Aug 2016 11:56:42 -0000	1.18
+++ include/atomic.h	1 May 2017 01:58:03 -0000
@@ -262,19 +262,11 @@ _atomic_sub_long_nv(volatile unsigned lo
 
 #define __membar(_f) do { __asm __volatile(_f ::: "memory"); } while (0)
 
-#ifdef MULTIPROCESSOR
-#define membar_enter()		__membar("mfence")
-#define membar_exit()		__membar("")
-#define membar_producer()	__membar("")
-#define membar_consumer()	__membar("")
-#define membar_sync()		__membar("mfence")
-#else
 #define membar_enter()		__membar("")
 #define membar_exit()		__membar("")
 #define membar_producer()	__membar("")
 #define membar_consumer()	__membar("")
 #define membar_sync()		__membar("")
-#endif
 
 /* virtio needs MP membars even on SP kernels */
 #define virtio_membar_producer()	__membar("")