#define wmb() barrier()
#define read_barrier_depends() do { } while(0)
#define set_mb(var, value) do { xchg(&var, value); } while (0)
#define wmb() barrier()
#define read_barrier_depends() do { } while(0)
#define set_mb(var, value) do { xchg(&var, value); } while (0)