throws InterruptedException {
    while (!isThreadBlockedOnInstanceOf(t, blocker)) {
      if (t.getState() == Thread.State.TERMINATED) {
        throw new RuntimeException("Thread " + t + " exited unexpectedly");
      }
      Thread.sleep(1);
    }
  }

  private static boolean isThreadBlockedOnInstanceOf(Thread t, Class<?> blocker) {