Add cmpxchg_local to xtensa

Use the architecture specific __cmpxchg_u32 for 32 bits cmpxchg)_local. Else,
use the new generic cmpxchg_local (disables interrupt).
Signed-off-by: NMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/asm-xtensa/system.h

@@ -156,8 +156,30 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
 	   			        (unsigned long)_n_, sizeof (*(ptr))); \
 	})
 
+#include <asm-generic/cmpxchg-local.h>
 
+static inline unsigned long __cmpxchg_local(volatile void *ptr,
+				      unsigned long old,
+				      unsigned long new, int size)
+{
+	switch (size) {
+	case 4:
+		return __cmpxchg_u32(ptr, old, new);
+	default:
+		return __cmpxchg_local_generic(ptr, old, new, size);
+	}
 
+	return old;
+}
+
+/*
+ * cmpxchg_local and cmpxchg64_local are atomic wrt current CPU. Always make
+ * them available.
+ */
+#define cmpxchg_local(ptr, o, n)				  	       \
+	((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
+			(unsigned long)(n), sizeof(*(ptr))))
+#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
 
 /*
  * xchg_u32