Method forward_task

benchmarks/tbb/flow_graph.h:2489–2542

only returns a valid task pointer or NULL, never SUCCESSFULLY_ENQUEUED

    // only returns a valid task pointer or NULL, never SUCCESSFULLY_ENQUEUED
    task *forward_task() {
        input_type v;
        task *rval = NULL;
        bool reserved = false;
            {
                spin_mutex::scoped_lock lock(my_mutex);
                if ( check_conditions() )
                    ++my_tries;
                else
                    return NULL;
            }

        //SUCCESS 
        // if we can reserve and can put, we consume the reservation 
        // we increment the count and decrement the tries
        if ( (my_predecessors.try_reserve(v)) == true ){
            reserved=true;
            if ( (rval = my_successors.try_put_task(v)) != NULL ){
                {
                    spin_mutex::scoped_lock lock(my_mutex);
                    ++my_count;
                    --my_tries;
                    my_predecessors.try_consume();
                    if ( check_conditions() ) {
                        task* tp = this->my_graph.root_task();
                        if ( tp ) {
                            task *rtask = new ( task::allocate_additional_child_of( *tp ) )
                                internal::forward_task_bypass< limiter_node<T> >( *this );
                            FLOW_SPAWN (*rtask);
                        }
                    }
                }
                return rval;
            }
        }
        //FAILURE
        //if we can't reserve, we decrement the tries
        //if we can reserve but can't put, we decrement the tries and release the reservation
        {
            spin_mutex::scoped_lock lock(my_mutex);
            --my_tries;
            if (reserved) my_predecessors.try_release();
            if ( check_conditions() ) {
                task* tp = this->my_graph.root_task();
                if ( tp ) {
                    task *rtask = new ( task::allocate_additional_child_of( *tp ) )
                        internal::forward_task_bypass< limiter_node<T> >( *this );
                    __TBB_ASSERT(!rval, "Have two tasks to handle");
                    return rtask;
                }
            }
            return rval;
        }
    }

    void forward() {
        __TBB_ASSERT(false, "Should never be called");