__thr_rwlock_rdlock
ret = __thr_rwlock_rdlock(&prwlock->lock, flags, abstime);
ret = __thr_rwlock_rdlock(rwlock, URWLOCK_PREFER_READER, NULL);
return (__thr_rwlock_rdlock(rwlock, flags, tsp));
int __thr_rwlock_rdlock(struct urwlock *rwlock, int flags,