w = x;
if (x->rtavl_rtag == RTAVL_THREAD)
  {
    x->rtavl_rtag = RTAVL_CHILD;
    y->rtavl_link[0] = NULL;
  }
else
  y->rtavl_link[0] = x->rtavl_link[1];
x->rtavl_link[1] = y;
x->rtavl_balance = y->rtavl_balance = 0;
