HSQ_INVALID_TAG
hsq->next_tag = HSQ_INVALID_TAG;
hsq->tail_tag = HSQ_INVALID_TAG;
hsq->tag_slot[hsq->next_tag] = HSQ_INVALID_TAG;
if (hsq->next_tag == HSQ_INVALID_TAG) {
hsq->tag_slot[hsq->tail_tag] = HSQ_INVALID_TAG;
hsq->next_tag = HSQ_INVALID_TAG;
hsq->tail_tag = HSQ_INVALID_TAG;
hsq->tag_slot[i] = HSQ_INVALID_TAG;