Tackling the indefinite/user DMA fence problem

[Simon Ser]

On Wednesday, May 25th, 2022 at 15:51, Daniel Vetter <daniel at ffwll.ch> wrote:

> > > Ofc in reality you can still flood your compositor and they're not very
> > > robust, but with umf it's trivial to just hang your compositor forever and
> > > nothing happens.
> >
> > You can add that to the list of reasons why compositors need to stop
> > using buffers with unsignaled fences. There's plenty of other reasons
> > there already (the big one being that otherwise slow clients can slow
> > down the compositor, even if the compositor uses a high priority context
> > and the HW supports preemption).
>
>
> Yeah that's tbh another reason why I think we shouldn't do umf as a
> transparent thing - compositors need to get better anyway, so we might as
> well take this as a chance to do this right.

As a compositor dev, I agree -- we should definitely be smarter about
this. Note, it would help a lot to have a good way to integrate the
waits into a poll(2) event loop.