if (unlikely(offsets.end_switch_old)) {
//ust// ltt_clear_noref_flag(chan, buf, SUBBUF_INDEX(offsets.old - 1, chan));
ltt_reserve_switch_old_subbuf(chan, buf, &offsets, tsc);
if (unlikely(offsets.end_switch_old)) {
//ust// ltt_clear_noref_flag(chan, buf, SUBBUF_INDEX(offsets.old - 1, chan));
ltt_reserve_switch_old_subbuf(chan, buf, &offsets, tsc);