ATA_TAG_POISON
link->active_tag = ATA_TAG_POISON;
qc->tag = ATA_TAG_POISON;
link->active_tag = ATA_TAG_POISON;
link->active_tag = ATA_TAG_POISON;
if (ap->link.active_tag == ATA_TAG_POISON)
ap->link.active_tag = ATA_TAG_POISON;
dq->tag[dq->head++ & (ATA_MAX_QUEUE - 1)] = ATA_TAG_POISON;
pp->last_issue_tag = ATA_TAG_POISON;