C#

b1<=b2<=e1
b1<=e2<=e1
b2<=b1<=e2
b2<=e1<=e2

namespace Test
{
    public class SyncQueue<T>
    {
        private Queue<T> queue;
        private object readerLock;
        private object queueLock;
        private AutoResetEvent dataAvailable;

        public SyncQueue()
        {
            this.queue = new Queue<T>();
            this.readerLock = new object();
            this.queueLock = new object();
            this.dataAvailable = new AutoResetEvent(false);
        }

        public void Enqueue(T item)
        {
            lock (queueLock)
            {
                queue.Enqueue(item);
                Console.WriteLine("Enqueued Item: " + item);
            }
            dataAvailable.Set();
        }

        public T Dequeue()
        {
            lock (readerLock)
            {
                if (queue.Count == 0)
                {
                    dataAvailable.WaitOne();
                }
                lock (queueLock)
                {
                    return queue.Dequeue();
                }
            }
        }
    }

    public class Tester
    {
        SyncQueue<int> myQ = null;

        public Tester(SyncQueue<int> queue)
        {
            myQ = queue;
        }

        public void ProcessMessages(object obj)
        {
            while (true)
            {
                Console.WriteLine(myQ.Dequeue());
            }
        }
    }

    public class Program
    {
        static void Main(string[] args)
        {
            SyncQueue<int> myQ = new SyncQueue<int>();
            Tester t1 = new Tester(myQ);
            Tester t2 = new Tester(myQ);
            Tester t3 = new Tester(myQ);
            ThreadPool.QueueUserWorkItem(new WaitCallback(t1.ProcessMessages));
            ThreadPool.QueueUserWorkItem(new WaitCallback(t2.ProcessMessages));
            ThreadPool.QueueUserWorkItem(new WaitCallback(t3.ProcessMessages));

            while (true)
            {
                string[] snumbs = Console.ReadLine().Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
                foreach (string snumb in snumbs)
                {
                    myQ.Enqueue(int.Parse(snumb));
                }
            }
        }
    }
}

dataAvailable.Reset() // Add this abouve WaitOne();
dataAvailable.WaitOne();