Index: sys/atomic.h
===================================================================
RCS file: /cvs/src/sys/sys/atomic.h,v
retrieving revision 1.4
diff -u -p -r1.4 atomic.h
--- sys/atomic.h	24 Jan 2017 22:22:20 -0000	1.4
+++ sys/atomic.h	3 May 2017 01:31:03 -0000
@@ -219,4 +219,10 @@ atomic_sub_long_nv(volatile unsigned lon
 #define membar_sync() __sync_synchronize()
 #endif
 
+/*
+ * instruction barrier
+ */
+
+#define barrier() __asm volatile("" ::: "memory")
+
 #endif /* _SYS_ATOMIC_H_ */
Index: dev/pci/drm/drm_linux.h
===================================================================
RCS file: /cvs/src/sys/dev/pci/drm/drm_linux.h,v
retrieving revision 1.49
diff -u -p -r1.49 drm_linux.h
--- dev/pci/drm/drm_linux.h	16 Apr 2017 17:16:21 -0000	1.49
+++ dev/pci/drm/drm_linux.h	3 May 2017 01:31:03 -0000
@@ -49,8 +49,6 @@ typedef off_t loff_t;
 #define __must_check
 #define __init
 
-#define barrier()		__asm __volatile("" : : : "memory");
-
 #define uninitialized_var(x) x
 
 #if BYTE_ORDER == BIG_ENDIAN