acquire (&rwlock->rw_spinlock);
__pthread_lock (&rwlock->rw_lock);
pthread_rwlock_destroy (pthread_rwlock_t *rwlock){  int readers;  _pthread_descr writer;  acquire (&rwlock->rw_spinlock);  readers = rwlock->rw_readers;  writer = rwlock->rw_writer;  release (&rwlock->rw_spinlock);  if (readers > 0 || writer != NULL)    return EBUSY;  return 0;}