Use QThreadPool inside a worker task





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2















I have QThreadPool which run some tasks.
I need also create new tasks in other tasks.
To do that i think implement something like following:



class Task : public QRunnable
{
QThreadPool *pool;
public:
Task (QThreadPool *p) : pool(p){}

void run()
{
static std::atomic<int> counter = ATOMIC_FLAG_INIT;
qDebug() << QThread::currentThreadId();

int c;
if ((c = counter.load(std::memory_order_acquire)) < 10) {
pool->start(new Task(pool));
counter.store(c + 1, std::memory_order_release);
}

}
};

int main(int argc, char *argv)
{
//...

QThreadPool threadPool;
threadPool.start(new Task(&threadPool));

//...
}


But I'm not sure that this is the right approach.










share|improve this question


















  • 2





    The general approach looks fine, but the seperate load/store of counter is unsafe (as it could be changed in between the calls). However, if you only use it to control the number of parallel task, you don't even need it. QThreadPool::setMaxThreadCount should be used to control this instead.

    – Felix
    Nov 24 '18 at 15:08











  • @Felix OK, thank you

    – Kri
    Nov 24 '18 at 17:49


















2















I have QThreadPool which run some tasks.
I need also create new tasks in other tasks.
To do that i think implement something like following:



class Task : public QRunnable
{
QThreadPool *pool;
public:
Task (QThreadPool *p) : pool(p){}

void run()
{
static std::atomic<int> counter = ATOMIC_FLAG_INIT;
qDebug() << QThread::currentThreadId();

int c;
if ((c = counter.load(std::memory_order_acquire)) < 10) {
pool->start(new Task(pool));
counter.store(c + 1, std::memory_order_release);
}

}
};

int main(int argc, char *argv)
{
//...

QThreadPool threadPool;
threadPool.start(new Task(&threadPool));

//...
}


But I'm not sure that this is the right approach.










share|improve this question


















  • 2





    The general approach looks fine, but the seperate load/store of counter is unsafe (as it could be changed in between the calls). However, if you only use it to control the number of parallel task, you don't even need it. QThreadPool::setMaxThreadCount should be used to control this instead.

    – Felix
    Nov 24 '18 at 15:08











  • @Felix OK, thank you

    – Kri
    Nov 24 '18 at 17:49














2












2








2








I have QThreadPool which run some tasks.
I need also create new tasks in other tasks.
To do that i think implement something like following:



class Task : public QRunnable
{
QThreadPool *pool;
public:
Task (QThreadPool *p) : pool(p){}

void run()
{
static std::atomic<int> counter = ATOMIC_FLAG_INIT;
qDebug() << QThread::currentThreadId();

int c;
if ((c = counter.load(std::memory_order_acquire)) < 10) {
pool->start(new Task(pool));
counter.store(c + 1, std::memory_order_release);
}

}
};

int main(int argc, char *argv)
{
//...

QThreadPool threadPool;
threadPool.start(new Task(&threadPool));

//...
}


But I'm not sure that this is the right approach.










share|improve this question














I have QThreadPool which run some tasks.
I need also create new tasks in other tasks.
To do that i think implement something like following:



class Task : public QRunnable
{
QThreadPool *pool;
public:
Task (QThreadPool *p) : pool(p){}

void run()
{
static std::atomic<int> counter = ATOMIC_FLAG_INIT;
qDebug() << QThread::currentThreadId();

int c;
if ((c = counter.load(std::memory_order_acquire)) < 10) {
pool->start(new Task(pool));
counter.store(c + 1, std::memory_order_release);
}

}
};

int main(int argc, char *argv)
{
//...

QThreadPool threadPool;
threadPool.start(new Task(&threadPool));

//...
}


But I'm not sure that this is the right approach.







multithreading qt c++11






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share|improve this question











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share|improve this question










asked Nov 24 '18 at 10:11









KriKri

3116




3116








  • 2





    The general approach looks fine, but the seperate load/store of counter is unsafe (as it could be changed in between the calls). However, if you only use it to control the number of parallel task, you don't even need it. QThreadPool::setMaxThreadCount should be used to control this instead.

    – Felix
    Nov 24 '18 at 15:08











  • @Felix OK, thank you

    – Kri
    Nov 24 '18 at 17:49














  • 2





    The general approach looks fine, but the seperate load/store of counter is unsafe (as it could be changed in between the calls). However, if you only use it to control the number of parallel task, you don't even need it. QThreadPool::setMaxThreadCount should be used to control this instead.

    – Felix
    Nov 24 '18 at 15:08











  • @Felix OK, thank you

    – Kri
    Nov 24 '18 at 17:49








2




2





The general approach looks fine, but the seperate load/store of counter is unsafe (as it could be changed in between the calls). However, if you only use it to control the number of parallel task, you don't even need it. QThreadPool::setMaxThreadCount should be used to control this instead.

– Felix
Nov 24 '18 at 15:08





The general approach looks fine, but the seperate load/store of counter is unsafe (as it could be changed in between the calls). However, if you only use it to control the number of parallel task, you don't even need it. QThreadPool::setMaxThreadCount should be used to control this instead.

– Felix
Nov 24 '18 at 15:08













@Felix OK, thank you

– Kri
Nov 24 '18 at 17:49





@Felix OK, thank you

– Kri
Nov 24 '18 at 17:49












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