Add cmpxchg64 and cmpxchg64_local to x86_64

Make sure that at least cmpxchg64_local is available on all architectures to use
for unsigned long long values.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Andi Kleen <ak@muc.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-x86/cmpxchg_64.h

@@ -124,11 +124,21 @@ static inline unsigned long __cmpxchg_local(volatile void *ptr,
 	return old;
 }
 
-#define cmpxchg(ptr,o,n)\
-	((__typeof__(*(ptr)))__cmpxchg((ptr),(unsigned long)(o),\
-					(unsigned long)(n),sizeof(*(ptr))))
-#define cmpxchg_local(ptr,o,n)\
-	((__typeof__(*(ptr)))__cmpxchg_local((ptr),(unsigned long)(o),\
-					(unsigned long)(n),sizeof(*(ptr))))
+#define cmpxchg(ptr, o, n)						\
+	((__typeof__(*(ptr)))__cmpxchg((ptr), (unsigned long)(o),	\
+					(unsigned long)(n), sizeof(*(ptr))))
+#define cmpxchg64(ptr, o, n)						\
+  ({									\
+	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\
+	cmpxchg((ptr), (o), (n));					\
+  })
+#define cmpxchg_local(ptr, o, n)					\
+	((__typeof__(*(ptr)))__cmpxchg_local((ptr), (unsigned long)(o),	\
+					(unsigned long)(n), sizeof(*(ptr))))
+#define cmpxchg64_local(ptr, o, n)					\
+  ({									\
+	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\
+	cmpxchg_local((ptr), (o), (n));					\
+  })
 
 #endif