Re: mutter: reduce server grabs for window creation

[Owen Taylor <otaylor redhat com>]

On Wed, 2013-12-18 at 13:36 -0600, Daniel Drake wrote:
> On Wed, Dec 18, 2013 at 11:58 AM, Owen Taylor <otaylor redhat com> wrote:
> > From the partial backtrace posted on the bug, it looks like the code
> > called in response to ::add-window is not drawing (which would be fairly
> > surprising) but doing other GL operations - in the backtrace deleting a
> > texture.
>
> Going deeper into the trace, actually the call to delete the texture
> is some code in our custom shell, running in a StWidget style_changed
> handler. Maybe that is questionable. We've seen the hang in other
> contexts too (e.g. window minimizing where mutter's idle_calc_showing
> takes a server grab and then emits some signals to the shell), maybe
> in less questionable cases. Either way I'm going to attempt to reduce
> the server grabbing according to your comments - moreso than the
> initial patch does.

It sounds like server grabs and your driver just aren't going to get
along very well. Chasing every place where you are using GL behind the
scenes could be tricky. If we can stop leaking server grabs out to
Javascript without compromising robustness, that would definitely be
better.

> > One thing that definitely should be noted is that we still have a server
> > grab over everything when this code is called from
> > meta_screen_manage_all_windows(). From a brief look, it appears to me
> > that this happens *after* we initialize Javascript, set up signal
> > connections, etc - so probably the only reason that your patch works for
> > you is that the driver's internal swap-buffers thread isn't doing
> > anything during initialization.
>
> My patch does remove the meta_display_grab() call made by
> meta_screen_manage_all_windows(). I'm not sure if it was necessary or
> not, I just noticed that it calls meta_window_new_with_attrs() too and
> decided to update it for the new semantics.

Ah, missed that. I would have probably commented negatively on it if I
had noticed it, but on analysis (see my other mail), I don't think it
actually has much point :-)

- Owen