Use atomic_dec_return().

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kernel/smp.c

@@ -198,7 +198,7 @@ void generic_smp_call_function_interrupt(void)
 
 		data->csd.func(data->csd.info);
 
-		refs = atomic_sub_return(1, &data->refs);
+		refs = atomic_dec_return(&data->refs);
 		WARN_ON(refs < 0);
 		if (!refs) {
 			spin_lock(&call_function.lock);