ti_prev
tiptr->ti_prev = prevptr;
tiptr->ti_prev = NULL;
prevptr = curptr->ti_prev;
nextptr->ti_prev = prevptr;
struct _ti_user *ti_prev; /* previous one */
eibnx_thr_info_t *ti_prev;
ti_prev = NULL;
ti_prev = ti;
if (ti_prev)
ti_prev->ti_next = ti_next;