[Qt-interest] Qthread takes a long time to stop

[william.crocker at analog.com]

> 
> Also, on close, while the main GUI thread is waiting for the helper 
> threads.., I get the following message dialog on Linux:
> 
>  
> 
> Warning:
> The Window “sampleapp” is not responding
> Force Quit the application?
> Yes-no
>


For me that is a known RedHat #4 bug.
(or so I am told)


>  
> 
> This appears very briefly..the application then closes before the user 
> has a chance to click on either yes or no..( probably because the wait 
> period is over..)
> 
>  
> 
> Any ideas why this could be happening and what I could do to prevent it?
> 
>  
> 
> Thanks,
> 
> Sarvesh
> 
>  
> 
> *From:* qt-interest-bounces at trolltech.com 
> [mailto:qt-interest-bounces at trolltech.com] *On Behalf Of *Scott Bloom
> *Sent:* Saturday, June 19, 2010 9:06 PM
> *To:* Qt-Interest
> *Subject:* Re: [Qt-interest] Qthread takes a long time to stop
> 
>  
> 
> You basiclly answered it yourself.
> 
> You need to shorten the getmessage and processMessage functions...
> 
> One very common technique, is inside the algorithms, query if they are 
> allowedToRun();
> 
> Ie..
> 
> HelperThread::getmessage()
> {
>     if( !allowedToRun() ) return;
>    step1();
>     if( !allowedToRun() ) return;
>     step2();
>     if( !allowedToRun() ) return;
>    step3();
> }
> 
> And the same for processMessage()..
> 
> But at some point you will get down to a 3rd party library call, which 
> you cant make any smaller... That will be the minimum wait time :(
> 
> Scott
> 
> 
> On 6/19/10 8:02 AM, "Sarvesh Saran" <Sarvesh.Saran at synopsys.com> wrote:
> 
> Hi,
>  
> I have a helper thread derived from QThread which runs in a forever 
> loop. Inside the loop it reads messages from a server , does some 
> processing of the messages and send the message to the Main GUI thread.
>  
> So the helper thread looks something like:
>  
> Helperthread::run()
> {
>                 while(allowedToRun())
>                 {
>                                 QString msg;
> getmessage(&msg); //read a message from the server
> processMessage(msg);
>                 }
> }
>  
> Helperthread::processMessage()
> {
> //lots of case statements here….(to identify message types) and lots of 
> message processing
> }
>  
> //this is a public slot called by the main GUI thread
> Helperthread::setAllowedToRun()
> {
> //set the flag to false;
> }
>  
> My problem is that when the main window gets a close signal, it sets the 
> flag to false and has to wait for a long time for the helper thread to 
> finish.
>  
> i.e in the main window on close :
>  
> MainWindow::closeEvent()
> {
> helperthread->setAllowedToRun(false);
> helperthread->wait();  //this takes a long time because the helper 
> thread’s processMessage is quiet big and takes a long while to return.
> }
>  
> Is there a way I can speed this up so that my main window does not have 
> to wait for a long time for the helper thread to exit ?
>  
>  
> Thanks,
> Sarvesh
> 
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