What are common concurrency pitfalls? [closed]

Answer 1

Calling public classes from within a lock causing a DeadLock

public class ThreadedClass
{
    private object syncHandle = new object();

    public event EventHandler Updated = delegate { };
    public int state = 0;

    public void DoSmething()
    {
        lock(syncHandle)
        {
            // some locked code
            state = 1;

            Updated(this, EventArgs.Empty);
        }
    }

    public int State { 
        get
        {
            int returnVal;
            lock(syncHandle)
                returnVal = state;
            return returnVal;            
        }
    }
}

You can't be certain what your client is going to call, Most likely they'll try to read the State property. Do this instead

public void DoSmething()
{
    lock(syncHandle)
    {
        // some locked code
        state = 1;
    }
    // this should be outside the lock
    Updated(this, EventArgs.Empty);
}