__sync_seqno
return seqno_later(__sync_seqno(p)[idx], seqno);
__sync_seqno(p)[idx] = seqno;
if (__sync_seqno(leaf)[idx] != seqno) {
__func__, idx, __sync_seqno(leaf)[idx], seqno);
i, __sync_seqno(p)[i]);