* {@code getUnchecked}, and threads with an odd index will call {@code get}. If the cache throws
   * exceptions, this difference may be visible in the returned List.
   */
  @SuppressWarnings("ThreadPriorityCheck") // TODO: b/175898629 - Consider onSpinWait.
  private static <K> List<Object> doConcurrentGet(
      LoadingCache<K, ?> cache, K key, int nThreads, CountDownLatch gettersStartedSignal)