Elegant ways to notify consumer when producer is done?

Question

I'm implementing a concurrent_blocking_queue with minimal functions:

//a thin wrapper over std::queue
template<typename T>
class concurrent_blocking_queue
{
    std::queue<T> m_internal_queue;
     //...
 public:
     void add(T const & item);
     T&   remove();
     bool empty();
};

I intend to use this for producer-consumer problem (I guess, it is where one uses such data structures?). But I'm stuck on one problem which is:

How to elegantly notify consumer when producer is done? How would the producer notify the queue when it is done? By calling a specifiic member function, say done()? Is throwing exception from the queue (i.e from remove function) a good idea?

I came across many examples, but all has infinite loop as if the producer will produce items forever. None discussed the issue of stopping condition, not even the wiki article.

Answer 1

I've simply introduced a dummy "done" product in the past. So if the producer can create "products" of, say, type A and type B, I've invented type "done". When a consumer encounters a product of type "done" it knows that further processing isn't required anymore.