docs: Node<E> last() {
          restartFromTail:
          for (;;)
              for (Node<E> t = tail, p = t, q;;) {
                  if ((q = p.next) != null &&
                      (q = (p = q).next) != null)
                      // Check for tail updates every other hop.
                      // If p == q, we are sure to follow tail instead.
                      p = (t != (t = tail)) ? t : q;
                  else if (p == t
                           // It is possible that p is NEXT_TERMINATOR,
                           // but if so, the CAS is guaranteed to fail.
                           || TAIL.compareAndSet(this, t, p))
                      return p;
                  else
                      continue restartFromTail;
              }
      }