gistfile1.scala

import java.util.concurrent.LinkedBlockingQueue
import java.util.concurrent.atomic.AtomicInteger

object Hotpotato {

  private val nwaiters = new AtomicInteger(0)
  private val executionQueue = new LinkedBlockingQueue[Function0[Unit]]

  def serialized(f: => Unit) {
    executionQueue offer { () => f }

    if (nwaiters.getAndIncrement() == 0) {
      do {
        val task = executionQueue.poll()
        assert(task ne null)
        task()
      } while (nwaiters.decrementAndGet() > 0)
    }
  }
}