readyQueues.addIfAbsent(taskQueue)
      } else {
        readyQueues.remove(taskQueue)
      }
    }

    if (coordinatorWaiting) {
      backend.coordinatorNotify(this@TaskRunner)
    } else {
      startAnotherThread()
    }
  }

  private fun beforeRun(task: Task) {
    assertLockHeld()

    task.nextExecuteNanoTime = -1L

          serialTaskQueue += queuedTask
          executeCallCount++
          isParallel = serialTaskQueue.size > 1
        }

        override fun nanoTime() = nanoTime

        override fun coordinatorNotify(taskRunner: TaskRunner) {
          taskRunner.assertLockHeld()
          check(waitingCoordinatorTask != null)

          // Queue a task to resume the waiting coordinator.
          serialTaskQueue +=