[Intel-gfx] [PATCH xf96-video-intel] DRI2GetMSC: Do not send a bogus ust when no drawable is not displayed

[Chris Wilson]

On Fri, Mar 29, 2013 at 03:13:35AM -0700, Stéphane Marchesin wrote:
> On Fri, Mar 29, 2013 at 2:07 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > On Fri, Mar 29, 2013 at 01:54:37PM +0800, Daniel Kurtz wrote:
> >> According to the opengl glx_sync_control spec, the Unadjusted System Time
> >> (or UST) is a 64-bit monotonically increasing counter that is available
> >> throughout the system:
> >> http://www.opengl.org/registry/specs/OML/glx_sync_control.txt
> >>
> >> Therefore, sending 0, even in this corner case, is out of spec.
> >> Instead, just return FALSE indicating that the operation could not be
> >> completed.
> >
> > The problem is that ends up sending BadDrawable back to the client,
> > which ends up killing many clients and a compositor or two due to the
> > unexpected error.
> >
> > Would you prefer querying pipe 0 in this case for the UST?
> 
> For us it comes down to the fact that we'd like something monotonous.
> So yes querying pipe 0 could work if it's enabled. But I wonder what
> do you do when you have no enabled pipe though? Return the last UST?

That's a problem as we would need a running pipe, which is not
guaranteed. I wonder if CLOCK_MONOTONIC would suffice?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre