I have several threads consuming tasks from a queue using something similar to the code below. The problem is that there is one type of task which cannot run while any other tasks are being processed.

Here is what I have:

while (true) // Threaded code
{
    while (true)
    {
        lock(locker)
        {
            if (close_thread)
                return;

            task = GetNextTask(); // Get the next task from the queue
        }

        if (task != null)
            break;

        wh.WaitOne(); // Wait until a task is added to the queue
    }

    task.Run();
}

And this is kind of what I need:

while (true)
{
    while (true)
    {
        lock(locker)
        {
            if (close_thread)
                return;

            if (disable_new_tasks)
            { 
                task = null; 
            }
            else
            {
                task = GetNextTask();
            }
        }

        if (task != null)
            break;

        wh.WaitOne();
    }

    if(!task.IsThreadSafe())
    {
        // I would set this to false inside task.Run() at 
        // the end of the non-thread safe task
        disable_new_tasks = true;  
        Wait_for_all_threads_to_finish_their_current_tasks(); 
    }

    task.Run();
}

The problem is I don't know how to achive this without creating a mess.