Question

See the following code:

boost::thread_group threads;
boost::barrier      barrier(10);
thing               pThing;

for( size_t i = 0; i < 10; ++i )
{
    threads.create_thread(
        [&barrier, &pThing]()
        {
            while( true )
            {
                // do some stuff with pThing
                if( barrier.wait() )    //  let all threads catch up before resettings, and only 1 thread resets
                    pThing.Reset();
                barrier.wait();         //  let all threads wait until the reset is completed
            }
        });
}

threads.join_all();

Questions:

1. Do I need a way to break the while(true) for the threads to exit correctly?
2. Will join_all() complete since all the threads are infinite looping?
3. what happens when a thread finishes its work, does it die?
4. Is barrier.wait() an interruption point?
5. Do interruption points just yield the thread?
6. What happens when the thread_group dies; Do I even need to join_all() if the thread group it going to die right afterwards anyway?

Answer 1

1. No, you can also terminate a thread with exception. Interruption exception is a clean way to do it.
2. Issue interrupt_all() call first.
3. Yes, it cannot be resumed.
4. Yes.
5. I don’t understand your question. Interruption point is a point at which ‘am-I-interrupted?’ flag is checked and if it’s true, exception is thrown. interrupt() call sets this flag on a thread and, additionally, makes the thread stop waiting if that’s what it’s doing currently.
6. As far as I understand, threads continue to exist, i.e. they are not somehow forced to die. You need to make sure threads do exit (which inherently depends on what code your threads execute), then join_all() and only then destroy the thread group object.