[Interest] Terminating a QThread

Tony Rietwyk tony at rightsoft.com.au
Sat Jun 22 04:41:10 CEST 2013

But a bool value can be cached indefinitely, so make sure you declare the flag as volatile!  





From: interest-bounces+tony=rightsoft.com.au at qt-project.org [mailto:interest-bounces+tony=rightsoft.com.au at qt-project.org] On Behalf Of Etienne Sandré-Chardonnal
Sent: Friday, 21 June 2013 9:01 PM
Cc: interest at qt-project.org
Subject: Re: [Interest] Terminating a QThread


Sorry Mandeep, I didn't read your post first. Basically what I posted is similar.

A mutex is a little bit overkill here, you could use an atomic variable if you want to be sure, but just a bool flag will be enough as it is always set atomically AFAIK


2013/6/21 Mandeep Sandhu <mandeepsandhu.chd at gmail.com>

On Fri, Jun 21, 2013 at 1:36 PM, francois cellier <f_cellier at yahoo.fr> wrote:

Dear all,

Even if I know that it can be dangerous to terminate a thread, I need to do it for my application.
The function that run into the thread is like a long linear sequence of code that has not been designed in a signal/slot way. Moreover, in my thread, I need an eventloop as I use in it some TCP or UDP  Qt sockets.

I have tried the worker approach with the following code and I did not find a way to terminate the thread :

For my thread class :

1.	ThreadEx::ThreadEx(QObject <http://qt-project.org/doc/QObject.html>  *parent) :

2.	    QThread <http://qt-project.org/doc/QThread.html> (parent)

3.	{

4.	}


6.	void ThreadEx::run()

7.	{

8.	    QThread <http://qt-project.org/doc/QThread.html> ::setTerminationEnabled(true);

9.	    exec();

10.	}

For my worker class:

1.	ObjectInThread::ObjectInThread(QObject <http://qt-project.org/doc/QObject.html>  *parent) :

2.	    QObject <http://qt-project.org/doc/QObject.html> (parent)

3.	{

4.	}



7.	void ObjectInThread::run()

8.	{

9.	   int compteur = 0;

10.	//here i am using a loop instead of the long linear flow  but it is not a loop  in the real code

11.	    while(1)

12.	    {

13.	        qDebug() <<compteur;

14.	        compteur++;

15.	        Sleep(1000);

16.	    }

17.	}

You use a condition variable in your loop here, which will exit out of the run() function. This variable can be set from your stop() slot (protected by a mutex if needed).

In your main(GUI) thread you can wait for your worker thread to exit:






This should cleanly exit the thread.

Moreover I tried the other way of using QThread that consists in inheriting the QThread class and overriding the run method with the code :

void ThreadEx::run()
    int compteur = 0;
         qDebug() <<compteur;

In that case terminate works but I do not have an eventloop as I did not call the exec method.

Is this the expected behaviour ?

I am using Qt5.1 on centOS / RedHat 6.2. I have also tried this on Windows with no more success.

Thanks for your help,





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