Re: How to properly exit a thread?

[Paul Davis <pjdavis engineering uiowa edu>]

Xiangfei,

Docs indicate doing something like this:

void
FrameNode::read_new_data()
{
   bool done = false ;
   while( !done )
   {
      [do something]
   }

   throw Glib::Thread::Exit() ;
}

(Although, as a side note, and without looking at the Glib::Thread code 
and basing everything off of my guess as to how this is implemented, 
throw Glib::Thread::Exit() is optional at the end, and is probably meant 
as a way to exit the thread "early".  Ie, don't call return ; Maybe 
someone with more experience on the Glib::Thread implementation coudl 
explain this a bit better, because it seems like an odd choice of 
implementation to me.)

What you've probably got at issue is guranteeing that all of your 
threads have exited before you attempt to close your program.  My guess 
is that you've got a thread waiting on a condtion variable when an 
attempt to destroy the condition variable is made.

Without any more info on what your thread is doing, I can't really say 
much else.

As a side note, if you create your thread as joinable, read->join() will 
block until the thread exits.  If you need to ensure that a thread has 
exited at some point in your software, this would be one method of doing 
so. (This is making some assumptions, like the spawned thread was 
required to finish before the spawning thread, if that makes any 
sense.)  The more general method is using one of the normal 
synchronization constructs.  Ie, a semaphore.

Hope that helps more than it confuses.

Paul


Xiangfei Jia wrote:

> I created a thread like this:
>
>     Glib::Thread *const read = 
> Glib::Thread::create(sigc::mem_fun(node, &FrameNode::read_new_data), 
> false);
>
> Sometimes, when I exit from my program I got this error message:
> GThread-ERROR **: file gthread-posix.c: line 247 (): error 'Device or 
> resource busy' during 'pthread_cond_destroy ((pthread_cond_t *) cond)'
> aborting...
> Aborted
>
>
> I looked at the Glib reference, I found out I should use
>
> throw Glib::Thread::Exit <http://www.gtkmm.org/docs/glibmm-2.4/docs/reference/html/classGlib_1_1Thread_1_1Exit.html>
> ();
>
> to exit my thread. But I don't really know how to use this properly. 
> Can anyone tell me how to use it please!!!!!
>
> Thanks in advance!
>
>
> Fei
>
>
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