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POMonitor.Wait() causing elements of the queue to be skipped
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  1. POMonitor.Wait() causing elements of the queue to be skipped
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    copied!<p>I'm trying to pass elements from one queue to the next as space becomes available. The FixedSizeQueue is from an example I saw <a href="https://stackoverflow.com/questions/530211/creating-a-blocking-queuet-in-net">here</a>. I was printing out the elements as they are added and removed from the queue but it turns out that some of them are skipped. I think it happens when Monitor.Wait(queue) is called. Can anyone help me to solve this?</p> <pre><code>class FixedSizeQueue&lt;T&gt; : Queue&lt;T&gt; { private readonly Queue&lt;T&gt; queue = new Queue&lt;T&gt;(); private readonly int maxSize; public FixedSizeQueue(int maxSize) { this.maxSize = maxSize; } public new void Enqueue (T item) { lock (queue) { while (queue.Count &gt;= maxSize) { Monitor.Wait(queue); } queue.Enqueue(item); if (queue.Count == 1) { // wake up any blocked dequeue Monitor.PulseAll(queue); } } } public new T Dequeue() { lock (queue) { while (queue.Count == 0) { Monitor.Wait(queue); } T item = queue.Dequeue(); if (queue.Count == maxSize - 1) { Monitor.PulseAll(queue); } return item; } } } class Program { static void AddCustomerToWaitingList(Queue&lt;Customer&gt; customers, FixedSizeQueue&lt;Customer&gt; waitingList) { Customer customer = new Customer(); for (int i = 0; i &lt; 40; i++) { customer = customers.Dequeue(); waitingList.Enqueue(customer); } } static void AddCustomerToEatingList(FixedSizeQueue&lt;Customer&gt; waitingList, FixedSizeQueue&lt;Customer&gt; eatingList) { Customer customer = new Customer(); for (int i = 0; i &lt; 40; i++) { customer = waitingList.Dequeue(); eatingList.Enqueue(customer); } } static void RemoveCustomerFromWaitingList(FixedSizeQueue&lt;Customer&gt; waitingList) { Customer customer = new Customer(); for (int i = 0; i &lt; 40; i++) { customer = waitingList.Dequeue(); } } static void RemoveCustomerFromEatingList(FixedSizeQueue&lt;Customer&gt; eatingList) { Customer customer = new Customer(); foreach(Customer c in eatingList) { customer = eatingList.Dequeue(); } } static void Main(string[] args) { Chef chef = new Chef(); Customer customer = new Customer(); Queue&lt;Customer&gt; customers = new Queue&lt;Customer&gt;(40); FixedSizeQueue&lt;Customer&gt; eatingList = new FixedSizeQueue&lt;Customer&gt;(7); FixedSizeQueue&lt;Customer&gt; waitingList = new FixedSizeQueue&lt;Customer&gt;(12); Thread cafeClock = new Thread(new ThreadStart(Cafe.StartCounting)); Thread addCustomerToWaitingList = new Thread(() =&gt; AddCustomerToWaitingList(customers, waitingList)); Thread removeCustomerFromWaitingList = new Thread(() =&gt; RemoveCustomerFromWaitingList(waitingList)); Thread addCustomerToEatingList = new Thread(() =&gt; AddCustomerToEatingList(waitingList,eatingList)); Thread removeCustomerFromEatingList = new Thread(() =&gt; RemoveCustomerFromEatingList(eatingList)); for (int i = 1; i &lt;= 40; i++) { customer.Id = i; customers.Enqueue(customer); customer = new Customer(); } addCustomerToWaitingList.Start(); removeCustomerFromWaitingList.Start(); addCustomerToEatingList.Start(); removeCustomerFromEatingList.Start(); Console.WriteLine("End"); } } </code></pre>
 

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