Add cmpxchg_local to blackfin, replace __cmpxchg by generic cmpxchg

Use the new generic cmpxchg_local (disables interrupt). Also use the generic
cmpxchg as fallback if SMP is not set since nobody seems to know why __cmpxchg
has been implemented in assembly in the first place thather than in plain C.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Bryan Wu <bryan.wu@analog.com>
Cc: Michael Frysinger <michael.frysinger@analog.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-blackfin/system.h

@@ -183,55 +183,20 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
 	return tmp;
 }
 
+#include <asm-generic/cmpxchg-local.h>
+
 /*
- * Atomic compare and exchange.  Compare OLD with MEM, if identical,
- * store NEW in MEM.  Return the initial value in MEM.  Success is
- * indicated by comparing RETURN with OLD.
+ * cmpxchg_local and cmpxchg64_local are atomic wrt current CPU. Always make
+ * them available.
  */
-static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
-				      unsigned long new, int size)
-{
-	unsigned long tmp = 0;
-	unsigned long flags = 0;
-
-	local_irq_save(flags);
-
-	switch (size) {
-	case 1:
-		__asm__ __volatile__
-			("%0 = b%3 (z);\n\t"
-			 "CC = %1 == %0;\n\t"
-			 "IF !CC JUMP 1f;\n\t"
-			 "b%3 = %2;\n\t"
-			 "1:\n\t"
-			 : "=&d" (tmp) : "d" (old), "d" (new), "m" (*__xg(ptr)) : "memory");
-		break;
-	case 2:
-		__asm__ __volatile__
-			("%0 = w%3 (z);\n\t"
-			 "CC = %1 == %0;\n\t"
-			 "IF !CC JUMP 1f;\n\t"
-			 "w%3 = %2;\n\t"
-			 "1:\n\t"
-			 : "=&d" (tmp) : "d" (old), "d" (new), "m" (*__xg(ptr)) : "memory");
-		break;
-	case 4:
-		__asm__ __volatile__
-			("%0 = %3;\n\t"
-			 "CC = %1 == %0;\n\t"
-			 "IF !CC JUMP 1f;\n\t"
-			 "%3 = %2;\n\t"
-			 "1:\n\t"
-			 : "=&d" (tmp) : "d" (old), "d" (new), "m" (*__xg(ptr)) : "memory");
-		break;
-	}
-	local_irq_restore(flags);
-	return tmp;
-}
+#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))
 
-#define cmpxchg(ptr,o,n)\
-        ((__typeof__(*(ptr)))__cmpxchg((ptr),(unsigned long)(o),\
-                                        (unsigned long)(n),sizeof(*(ptr))))
+#ifndef CONFIG_SMP
+#include <asm-generic/cmpxchg.h>
+#endif
 
 #define prepare_to_switch()     do { } while(0)