Threading problem with deadlock (New to threading)

Question

4.00/5 (1 vote)

See more:

Hello there!
I think I need your help again. This time it's about threading.
I have my GUI starting my child thread. And the thread starts without problems *yay*
But when I want to call "Stop" or "GoOn", i get something like a deadlock.
Here is my code running in the thread:

C#

public class MixUpdater
{
    private volatile bool MixUpdaterShouldStop = false;
    public bool MixUpdaterStopped { get; private set; }
    volatile object locker = new object( );
    private bool MixerUpdaterGoOn = false;

    public void UpdateMixes(object o)
    {

        //varible declaration etc.

        for ( int i = 1; i <= max; i++ )
        {
            resp = eightTracksConnection.GetMixes(null, genres, 25, sortType, i);

            Debug.WriteLine("Baby says " + Thread.CurrentThread.ManagedThreadId);

            if ( i == 1 )
                max = resp.TotalPages;
            else
            {
                while ( !MixerUpdaterGoOn )
                {
                    if ( MixUpdaterShouldStop )
                        break;
                    Thread.Sleep(10);
                }
            }

            foreach ( Mix m in resp.Mixes )
            {
                dispatcher.Invoke((Action)( ( ) => { Mixes.Add(m); } ), null);
            }

            MixerUpdaterGoOn = false;
        }

        MixUpdaterStopped = true;

    }

    public void RequestStop( )
    {
        MixUpdaterShouldStop = true;
    }

    public void LoadMore( )
    {
        MixerUpdaterGoOn = true;
    }
}

To stop it (at least I try) I use the following code:

C#

if ( MixListUpdaterThread != null )
{
  MixListUpdater.RequestStop( );
  while ( !MixListUpdater.MixUpdaterStopped )
    Thread.Sleep(10);
}

Also the "LoadMore"-Method doesn't work.

I think it is because of the "Thread.Sleep"s, but I cant figure it out.
I also don't know if I should use lock() and where.

I hope you can help me.

Thanks, Markus

Posted 27-Sep-12 4:00am

NeonMika

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Stephen Hewison · Accepted Answer · 2012-09-27T04:12:00

You should probably take a look at the Monitor class.

System.Threading.Monitor

Using Invoke performs a thread synchronisation and I normally only use it to allow background threads to update UI elements.

I normally use a code sample similar to this when I have multiple threads access objects in the background:

C#

public class MixCollection()
{

  public delegate void MixAdded(Mix mix);
  public event MixAdded OnMixAdded;

  private List<Mix> _theList = new List<Mix>();

  public void Add(Mix item)
  {
    bool complete = false;
    while(!complete)
    {
      if(System.Threading.Monitor.TryEnter(_theList, 100))
      {
        try
        {
          complete = true;
          _theList.Add(item);
          if(OnMixAdded != null)
            OnMixAdded(item);
        }
        finally
        {
          System.Threading.Monitor.Exit(_theList);
        }
      }
      else
        System.Threading.Thread.Sleep(100);
    }
  }

}

public class MixUpdater()
{

  private Thread _bgThread;
  private MixCollection _mixes;

  public MixUpdater(MixCollection mixes)
  {
    _mixes = mixes;
    Start();
  }

  private bool _stop = false;

  public void Stop() { _stop = true; }
  public void Start()
  {
    if(_stop)
    {
      _bgThread = new Thread(new ThreadStart(Work));
      _bgThread.Start();
    }
  }

  private void Work()
  {
    while(!_stop)
    {
      //do your mix check here adding new items doing the following where you get a new mix
      _mixes.Add(mix);
      
      Thread.Sleep(1000);
    }
  }

}

Then in your UI:

Note although back in your UI class, the thread bubbling the event is still a background thread and as such you need to invoke to update your UI.

C#

public class MyForm : Form
{

  MixCollection _mixes;
  MixUpdater _mixUpdater;

  public MyForm()
  {
    _mixes = new MixCollection();
    _mixes.OnMixAdded += new MixCollection.MixAdd(OnMixAdded);
    _mixUpdater = new MixUpdater(_mixes);
  }

  public void OnMixAdded(Mix mix)
  {
    ListBox.dispatcher.Invoke((Action)( ( ) => { ListBox.Items.Add(mix); } ), null);
  }

}

I've typed all this off the top of my head, so I'm sorry if it's not quite right in your project, but you should get the general idea.