int pthread_rwlock_init (pthread_rwlock_t *rwlock,
                         const pthread_rwlockattr_t *attr);
int pthread_rwlock_destroy (pthread_rwlock_t *rwlock);

int pthread_rwlock_rdlock (pthread_rwlock_t *rwlock);
int pthread_rwlock_wrlock (pthread_rwlock_t *rwlock);

int pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock);
int pthread_rwlock_trywrlock (pthread_rwlock_t *rwlock);

int pthread_rwlock_unlock (pthread_rwlock_t *rwlock);