[PATCH] atomic: cmpxchg

Introduce an atomic_cmpxchg operation.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/asm-x86_64/atomic.h b/include/asm-x86_64/atomic.h
index fc4c5956e1ea..75c8a1e96737 100644
--- a/include/asm-x86_64/atomic.h
+++ b/include/asm-x86_64/atomic.h
@@ -360,6 +360,8 @@ 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_inc_return(v)  (atomic_add_return(1,v))
 #define atomic_dec_return(v)  (atomic_sub_return(1,v))