}
    } finally {
      readCompleteLatch.countDown()
    }
  }

  abstract fun listSource(): Source

  override fun ensureLoaded() {
    if (!listRead.get() && listRead.compareAndSet(false, true)) {
      readTheListUninterruptibly()
    } else {
      try {
        readCompleteLatch.await()
      } catch (_: InterruptedException) {