fun cancelAll() {
    taskRunner.assertLockNotHeld()

    taskRunner.withLock {
      if (cancelAllAndDecide()) {
        taskRunner.kickCoordinator(this)
      }
    }
  }

  fun shutdown() {
    taskRunner.assertLockNotHeld()

    taskRunner.withLock {
      shutdown = true
      if (cancelAllAndDecide()) {
        taskRunner.kickCoordinator(this)
      }
    }
  }

    }
  }

  fun cancelAll() {
    assertLockHeld()
    for (i in busyQueues.size - 1 downTo 0) {
      busyQueues[i].cancelAllAndDecide()
    }
    for (i in readyQueues.size - 1 downTo 0) {
      val queue = readyQueues[i]
      queue.cancelAllAndDecide()
      if (queue.futureTasks.isEmpty()) {
        readyQueues.removeAt(i)
      }
    }
  }

  interface Backend {