From cee21041cf5b514eb1a6f17082d36da29e5dba34 Mon Sep 17 00:00:00 2001
From: Hans Petter Selasky <hselasky@FreeBSD.org>
Date: Mon, 21 Dec 2015 10:56:38 +0000
Subject: [PATCH] Implement ACCESS_ONCE(), WRITE_ONCE() and READ_ONCE().

MFC after:	1 week
Sponsored by:	Mellanox Technologies
---
 .../linuxkpi/common/include/linux/compiler.h     | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/sys/compat/linuxkpi/common/include/linux/compiler.h b/sys/compat/linuxkpi/common/include/linux/compiler.h
index 638135845b7..b6ea98f1875 100644
--- a/sys/compat/linuxkpi/common/include/linux/compiler.h
+++ b/sys/compat/linuxkpi/common/include/linux/compiler.h
@@ -72,4 +72,20 @@
 
 #define	barrier()			__asm__ __volatile__("": : :"memory")
 
+#define	ACCESS_ONCE(x)			(*(volatile __typeof(x) *)&(x))
+  
+#define	WRITE_ONCE(x,v) do {		\
+	barrier();			\
+	ACCESS_ONCE(x) = (v);		\
+	barrier();			\
+} while (0)
+
+#define	READ_ONCE(x) ({			\
+	__typeof(x) __var;		\
+	barrier();			\
+	__var = ACCESS_ONCE(x);		\
+	barrier();			\
+	__var;				\
+})
+  
 #endif	/* _LINUX_COMPILER_H_ */
-- 
2.45.2