Re: Gnome/Gtk and thread safety

[Maciej Stachowiak <mjs eazel com>]

Havoc Pennington <hp redhat com> writes:

> "Ryan C. Gordon" <icculus lokigames com> writes: 
> > ...and making something thread safe is never a bad idea, is it?
> > 
> 
> I'm no threads expert, but my impression is that making GTK
> transparently threadsafe would break tons of API (or leave lots of
> legacy API that wasn't safe) and would cause a not insignificant
> performance hit.
> 
> One of the nastiest problems is that for threadsafety you need
> everyone to own a reference to all objects they are using at all
> times; in this common code the application doesn't own a reference:
> 
>  GtkWidget *widget;
> 
>  widget = gtk_window_new ();
>  
> You'd need to add the reference as follows: 
> 
>  widget = gtk_window_new ();
>  g_object_ref (widget);
> 
> As you probably realize that doesn't work, there's a race condition
> where another thread can destroy the window (same thing applies to any
> widget). To avoid this condition you have to have all routines that
> return objects return a new reference.

We could take the classical Unix approach to fixing non-threadsafe
interfaces:

  widget = gtk_window_new_r ();

:-)


Actually, I don't get why the code you posted above with
gtk_window_new has a race; how could another thread even have access
to the value of `widget' right after you assign it, let alone want to
sink or unref it?

 - Maciej