if(future->state == NOT_EXECUTING)
    { /* execute it */

        // which queue is future in
        if(future->creator_id == -1)
        {
            pthread_mutex_lock(&future->pool->global_queue_lock);
            list_remove(&future->elem);
            pthread_mutex_unlock(&future->pool->global_queue_lock);
        }
        else
        {
            struct worker * worker = worker_for_id(future->creator_id);
            pthread_mutex_lock(&worker->queue_lock);
            list_remove(&future->elem);
            pthread_mutex_unlock(&worker->queue_lock);
        }

        // is current thread main or worker
        if(thread_worker == NULL)
        {
            future->state = EXECUTING;
            future->worker_id = -2;
            future->result = future->task(future->pool, future->data);
            future->state = FINISHED;
            sem_post(future->sem);
            return future->result;
        }
        else
        {
            future->state = EXECUTING;
            future->worker_id = thread_worker->worker_id;
            thread_worker->is_working = true;
            future->result = future->task(future->pool, future->data);
            future->state = FINISHED;
            thread_worker->is_working = false;
            sem_post(future->sem);
            return future->result;
        }
    }