[RFC 1/8] dma-buf/fence: add fence_collection fences

[Daniel Vetter]

On Fri, Apr 15, 2016 at 11:29:34AM -0700, Gustavo Padovan wrote:
> 2016-04-15 Daniel Vetter <daniel at ffwll.ch>:
> 
> > On Fri, Apr 15, 2016 at 11:03 AM, Christian König
> > <christian.koenig at amd.com> wrote:
> > > Might be that how amdgpu uses the fence context and sequence number is a bit
> > > questionable, but this will completely break it.
> > 
> > You mean it tries to qualesce fences in the same context down to just
> > the last one? That's how it's supposed to be done, and
> > fence_collections do break this somewhat. Without fixing up
> > fence_is_later and friends. Sounds like amdgpu is a good use case to
> > make sure the changes in semantics in these functions result in
> > sensible code. In a way a fence_collection is a fence where the
> > timeline never matches with any other timeline (since it's a
> > combiation).
> > 
> > And yeah I think fence_collection should probably compress down the
> > fences to 1 per timeline. But then that's just an implementation
> > detail we can fix later on.
> 
> You mean asking for a new context for every collection?

That would be one solution, but I fear it's a bit expensive. Having a
special-case context for collections might be the better approach.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch