struct rtrb_node *y = w->rtrb_link[1];
y->rtrb_color = RTRB_BLACK;
w->rtrb_color = RTRB_RED;
w->rtrb_link[1] = y->rtrb_link[0];
y->rtrb_link[0] = w;
w = pa[k - 1]->rtrb_link[0] = y;

if (w->rtrb_link[0]->rtrb_link[1] == NULL)
  {
    w->rtrb_link[0]->rtrb_rtag = RTRB_THREAD;
    w->rtrb_link[0]->rtrb_link[1] = w;
  }
