Add cmpxchg64 and cmpxchg64_local to alpha

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: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-alpha/system.h

@@ -681,13 +681,18 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
 	return old;
 }
 
-#define cmpxchg(ptr,o,n)						 \
+#define cmpxchg(ptr, o, n)						 \
   ({									 \
      __typeof__(*(ptr)) _o_ = (o);					 \
      __typeof__(*(ptr)) _n_ = (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));					 \
+  })
 
 static inline unsigned long
 __cmpxchg_u8_local(volatile char *m, long old, long new)
@@ -803,13 +808,19 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
 	return old;
 }
 
-#define cmpxchg_local(ptr,o,n)						 \
+#define cmpxchg_local(ptr, o, n)					 \
   ({									 \
      __typeof__(*(ptr)) _o_ = (o);					 \
      __typeof__(*(ptr)) _n_ = (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 /* __ASSEMBLY__ */