ARM: 7853/1: cmpxchg: implement cmpxchg64_relaxed

This patch introduces cmpxchg64_relaxed for arm, which performs a 64-bit
cmpxchg operation without barrier semantics. cmpxchg64_local is updated
to use the new operation.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/cmpxchg.h

@@ -270,11 +270,13 @@ static inline unsigned long long __cmpxchg64_mb(unsigned long long *ptr,
 					(unsigned long long)(o),	\
 					(unsigned long long)(n)))
 
-#define cmpxchg64_local(ptr, o, n)					\
+#define cmpxchg64_relaxed(ptr, o, n)					\
 	((__typeof__(*(ptr)))__cmpxchg64((ptr),				\
 					(unsigned long long)(o),	\
 					(unsigned long long)(n)))
 
+#define cmpxchg64_local(ptr, o, n)	cmpxchg64_relaxed((ptr), (o), (n))
+
 #endif	/* __LINUX_ARM_ARCH__ >= 6 */
 
 #endif /* __ASM_ARM_CMPXCHG_H */