Is it safe to call QThread::start() many times?

[qwe3]

Hi,

Is it safe to quit and start the same QThread many times like this:

QObject::connect(this, &MainWindow::doSomething, worker, &Worker::doSomething);
....

void MainWindow::on_pushButton_clicked() // cancel
{
    thread->requestInterruption();
    thread->quit();
    thread->wait();
}

void MainWindow::on_pushButton_2_clicked() // start
{
    thread->start();
    emit doSomething();
}

?

[jsulm]

@qwe3 Should be fine. If the thread is already running second start() call will not do anything.

[Pl45m4]

@qwe3 said in Is it safe to call QThread::start() many times?:

void MainWindow::on_pushButton_2_clicked() // start
{
thread->start();
emit doSomething();
}

You could replace this with a connection to
connect(thread, &QThread::started, worker, &Worker::DoWork)

Then start the thread when needed.

@qwe3 said in Is it safe to call QThread::start() many times?:

thread->requestInterruption();

Do you handle this properly?

[qwe3]

@jsulm Thank you!
@Pl45m4 I don't know it is correct, but I have :

void Worker::doSomething()
{
    for(long long i = 0; i < 1000000000; i++)
    {
        if(QThread::currentThread()->isInterruptionRequested())
        {
            return;
        }
        if(i%10000000 == 0)
        {
            qDebug()<<i;
        }
    }
    qDebug()<<"end";
}

[Pl45m4]

@qwe3 said in Is it safe to call QThread::start() many times?:

if(QThread::currentThread()->isInterruptionRequested())
{
return;
}

Looks good.

• https://doc.qt.io/qt-5/qthread.html#isInterruptionRequested