#include "pthread_impl.h"

int pthread_rwlock_unlock(pthread_rwlock_t* rw) {
  int val, cnt, waiters, new, priv = rw->_rw_shared ^ 128;

  do {
    val = rw->_rw_lock;
    cnt = val & 0x7fffffff;
    waiters = rw->_rw_waiters;
    new = (cnt == 0x7fffffff || cnt == 1) ? 0 : val - 1;
  } while (a_cas(&rw->_rw_lock, val, new) != val);

  if (!new && (waiters || val < 0))
    __wake(&rw->_rw_lock, cnt, priv);

  return 0;
}