[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, 13 insertions, 0 deletions

diff --git a/include/asm-cris/atomic.h b/include/asm-cris/atomic.h
index 8c2e78304523..45891f7de00f 100644
--- a/include/asm-cris/atomic.h
+++ b/include/asm-cris/atomic.h
@@ -123,6 +123,19 @@ static inline int atomic_inc_and_test(volatile atomic_t *v)
         return retval;
 }
 
+static inline int atomic_cmpxchg(atomic_t *v, int old, int new)
+{
+        int ret;
+        unsigned long flags;
+
+        cris_atomic_save(v, flags);
+        ret = v->counter;
+        if (likely(ret == old))
+                v->counter = new;
+        cris_atomic_restore(v, flags);
+        return ret;
+}
+
 /* Atomic operations are already serializing */
 #define smp_mb__before_atomic_dec()    barrier()
 #define smp_mb__after_atomic_dec()     barrier()