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Subject[PATCH 03/09] atomic.h : i386 type safety fix
atomic.h : i386 type safety fix

This patch removes an explicit cast to an integer type for the result returned
by cmpxchg. It is not per se a problem on the i386 architecture, because
sizeof(int) == sizeof(long), but whenever this code is cut'n'pasted to a
different architecture (which happened at least for x86_64), it would simply
accept passing an atomic64_t value as parameter to cmpxchg, xchg and
add_unless, having 64 bits inputs casted to 32 bits.

Signed-off-by: Mathieu Desnoyers <>

--- a/include/asm-i386/atomic.h
+++ b/include/asm-i386/atomic.h
@@ -207,8 +207,9 @@ static __inline__ int atomic_sub_return(int i, atomic_t *v)
return atomic_add_return(-i,v);

-#define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new))
-#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
+#define atomic_cmpxchg(v, old, new) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), (old), (new)))
+#define atomic_xchg(v, new) (xchg(&((v)->counter), (new)))

* atomic_add_unless - add unless the number is a given value
@@ -221,7 +222,7 @@ static __inline__ int atomic_sub_return(int i, atomic_t *v)
#define atomic_add_unless(v, a, u) \
({ \
- int c, old; \
+ __typeof__((v)->counter) c, old; \
c = atomic_read(v); \
for (;;) { \
if (unlikely(c == (u))) \
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