Author: hselasky
Date: Mon Dec 21 10:56:38 2015
New Revision: 292537
URL: https://svnweb.freebsd.org/changeset/base/292537
Log:
Implement ACCESS_ONCE(), WRITE_ONCE() and READ_ONCE().
MFC after: 1 week
Sponsored by: Mellanox Technologies
Modified:
head/sys/compat/linuxkpi/common/include/linux/compiler.h
Modified: head/sys/compat/linuxkpi/common/include/linux/compiler.h
==============================================================================
--- head/sys/compat/linuxkpi/common/include/linux/compiler.h Mon Dec 21
09:38:45 2015 (r292536)
+++ head/sys/compat/linuxkpi/common/include/linux/compiler.h Mon Dec 21
10:56:38 2015 (r292537)
@@ -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_ */
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