acquire (&rwlock->rw_spinlock);
__pthread_lock (&rwlock->rw_lock);
pthread_rwlock_trywrlock (pthread_rwlock_t *rwlock){  int result = EBUSY;  acquire (&rwlock->rw_spinlock);  if (rwlock->rw_readers == 0 && rwlock->rw_writer == NULL)    {      rwlock->rw_writer = thread_self ();      result = 0;    }  release (&rwlock->rw_spinlock);  return result;}