how to stop running thread and resume the same thread beside create new thread?

Question

I have using concurrent_queue.h to have queue that receive element from different thread -

Every time some thread add element to the concurrent queue i call some method that create new thread to get element from the queue and handle it ( calling some method that do something with this item )

concurrency::concurrent_queue<Item> _queue;


void handleItem(Item item)
{
    // do something with item  
}

// method that call every time add something to the queue - can be 
// situation that the queue contain more then one item 
void handleQueueItem()
{
    Item item;
    while (_queue.try_pop(item))
    {
        std::thread t1(&handleItem, item);      

        t1.join();      // wait till finish before handle next item.        
    }
}

I want to make the thread t1 in other way that i will not need to create new thread evry time i have something in the queue

I don't know how to do it.

Answer 1

Instead of spinning up a thread in handleQueueItem , you can make handleQueueItem run in its own thread and it will run continuously. That would look like

void handleItem(Item item)
{
    // do something with item  
}

void handleQueueItem()
{
    Item item;
    while (_queue.try_pop(item))
    {  
        handleItem(item)
    }
}

std::thread runner([](){ handleQueueItem(); });

You can even add a flag to the loop so you can stop the thread by adding a std::atomic<bool> variable and checking it in the loop like

std::atomic<bool> run = true;
void handleQueueItem()
{
    Item item;
    while (run && _queue.try_pop(item))
    {  
        handleItem(item)
    }
}

std::thread runner([](){ handleQueueItem(); });

// later on
run = false;
runner.join();

And then all you need to do is run = false; to have the loop stop.