Question

The below code handles a socket message coming in with a 2 parameters. It puts information into a queue and is processed on another thread. My question is if 2 messages come in right after the other and are then dequeued and sent to the method ProcessData, is there a race condition on ProcessData?

private void DataIn(long Code, string Message)
{
  if (!Started)
  {
    if (DataInQueue == null)
      DataInQueue = new Queue();
    DataInThread = new Thread(new ThreadStart(ThreadProcedure));
    DataInThreadEnding = false;
    DataInThread.IsBackground = true;
    DataInThread.Start();
    Started = true;
  }
  DataInQueue.Enqueue(new cDataIn(Code, Message));
}

private void ThreadProcedure()
{
   while (!ProgramEnding)
   {
     Queue mySyncdQ = Queue.Synchronized(DataInQueue);
     if (mySyncdQ != null && mySyncdQ.Count > 0)
     {
        cDataIn data = null;
        // Creates a synchronized wrapper around the Queue. 
        if (mySyncdQ.Count > 0)
          data = (cDataIn)mySyncdQ.Dequeue();

        ProcessData(data);
    }
  }

}

Answer 1

UPDATE

Queue is not used in a thread-safe manner in your code… the code you show is not enough to be sure whether there is a race condition but with the ConcurrentQueue you get a better performance… and in the ThreadProcedure you can have calling ProcessData with null and as far as I can tell to be on the safe side ProcessData should be reentrant for all this to work…

Use a ConcurrentQueue – that avoids some possible problems… and check out BlockingCollection which is designed for thread-safe Producer/Consumer scenarios… both work mostly lock-free and are really fast…