Add cmpxchg64 and cmpxchg64_local to powerpc

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>
Acked-by: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-powerpc/system.h

@@ -463,7 +463,7 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
 	return old;
 }
 
-#define cmpxchg(ptr,o,n)						 \
+#define cmpxchg(ptr, o, n)						 \
   ({									 \
      __typeof__(*(ptr)) _o_ = (o);					 \
      __typeof__(*(ptr)) _n_ = (n);					 \
@@ -472,7 +472,7 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
   })
 
 
-#define cmpxchg_local(ptr,o,n)						 \
+#define cmpxchg_local(ptr, o, n)					 \
   ({									 \
      __typeof__(*(ptr)) _o_ = (o);					 \
      __typeof__(*(ptr)) _n_ = (n);					 \
@@ -492,6 +492,20 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
  */
 #define NET_IP_ALIGN	0
 #define NET_SKB_PAD	L1_CACHE_BYTES
+
+#define cmpxchg64(ptr, o, n)						\
+  ({									\
+	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\
+	cmpxchg((ptr), (o), (n));					\
+  })
+#define cmpxchg64_local(ptr, o, n)					\
+  ({									\
+	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\
+	cmpxchg_local((ptr), (o), (n));					\
+  })
+#else
+#include <asm-generic/cmpxchg-local.h>
+#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
 #endif
 
 #define arch_align_stack(x) (x)