[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, 14 insertions, 0 deletions

diff --git a/include/asm-v850/atomic.h b/include/asm-v850/atomic.h
index 395268a8c0de..e497166ca42b 100644
--- a/include/asm-v850/atomic.h
+++ b/include/asm-v850/atomic.h
@@ -90,6 +90,20 @@ static __inline__ void atomic_clear_mask (unsigned long mask, unsigned long *add
 #define atomic_dec_and_test(v)          (atomic_sub_return (1, (v)) == 0)
 #define atomic_add_negative(i,v)        (atomic_add_return ((i), (v)) < 0)
 
+static inline int atomic_cmpxchg(atomic_t *v, int old, int new)
+{
+        int ret;
+        unsigned long flags;
+
+        local_irq_save(flags);
+        ret = v->counter;
+        if (likely(ret == old))
+                v->counter = new;
+        local_irq_restore(flags);
+
+        return ret;
+}
+
 /* Atomic operations are already serializing on ARM */
 #define smp_mb__before_atomic_dec()     barrier()
 #define smp_mb__after_atomic_dec()      barrier()