QH_UNLINK_QUEUE_EMPTY
qh->unlink_reason |= QH_UNLINK_QUEUE_EMPTY;
else if ((qh->unlink_reason & QH_UNLINK_QUEUE_EMPTY) &&
qh_to_unlink->unlink_reason |= QH_UNLINK_QUEUE_EMPTY;
qh->unlink_reason |= QH_UNLINK_QUEUE_EMPTY;