Re: gdk_threads_enter() hangs

[Todd Fisher <taf2 lehigh edu>]

Hi Frank,

   this is most likely because you are either:

a. not initializing the threading system correctly.
b. calling gdk_threads_enter within the main thread.

for example in main you should make sure you're initalizing gtk+ similar 
to the following:

int main( int argc, char **argv )
{
 /* thread init */
 g_thread_init( NULL );
 gdk_threads_init();
 gtk_init( &argc, &argv );

...

 gdk_threads_enter();
 gtk_main();
 gdk_threads_leave();
 return 0;
}

to satisfy condition b make sure you are not calling 
gdk_threads_enter/leave within any callbacks

main(){
...
g_signal_connect( obj, "clicked", func, NULL );
...
}
void tfunc( gpointer null )
{
  gdk_threads_enter();
/* update some graphical indicator */
  gdk_threads_leave();
}
void func( GtkWidget *widget, gpointer null )
{
   GThread *tid;
   /* gdk_threads_enter(); ERROR this would cause a dead lock such as 
the one you describe because
     main thread already holds the lock */
   tid = g_thread_create( tfunc, NULL, FALSE, NULL );
}
for a more complete example: 
severna.homeip.net/source/examples/simple.tar.gz

hope this helps,

-todd

Frank W. Miller wrote:

> Greetings,
>
> I'm having some strange behaviour.  I am writing a threaded Gnome app 
> and it seems to be hanging when I call gdk_threads_enter().  Here's 
> the code snippet where it hangs up:
>
> >                                                                                
> >  
> > printf("gdk_threads_enter()\n");
> >                 gdk_threads_enter();
> > printf("gdk_threads_enter() returned\n");
> >                                                                                
> >  
>
>
>
> The output is (as you might guess):
>
> > gdk_threads_enter()
>
>
>
> The second printf is never executed.  I've been over all my various 
> gdk_threads_enter()/gdk_threads_leave() pairs to make sure I'm not 
> locking GDK and then not unlocking it.  It seems to me to be fine.  
> All the protected areas are very short, i.e. 1 or 2 lines of code, and 
> the protected code is all just calls to gtk stuff.  I'm not doing any 
> I/O inside of a protected area.  Any thoughts on this?
>
>
> Thanks in advance,
> FM
>
>
>
>
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