Am 23.05.2016 um 09:41 schrieb Daniel Vetter:
On Fri, May 20, 2016 at 11:47:28AM -0300, Gustavo Padovan wrote:
2016-05-20 Christian König <deathsimple@xxxxxxxxxxx>:
From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
struct fence_collection inherits from struct fence and carries a
collection of fences that needs to be waited together.
It is useful to translate a sync_file to a fence to remove the complexity
of dealing with sync_files on DRM drivers. So even if there are many
fences in the sync_file that needs to waited for a commit to happen,
they all get added to the fence_collection and passed for DRM use as
a standard struct fence.
That means that no changes needed to any driver besides supporting fences.
fence_collection's fence doesn't belong to any timeline context, so
fence_is_later() and fence_later() are not meant to be called with
fence_collections fences.
v2: Comments by Daniel Vetter:
- merge fence_collection_init() and fence_collection_add()
- only add callbacks at ->enable_signalling()
- remove fence_collection_put()
- check for type on to_fence_collection()
- adjust fence_is_later() and fence_later() to WARN_ON() if they
are used with collection fences.
v3: - Initialize fence_cb.node at fence init.
Comments by Chris Wilson:
- return "unbound" on fence_collection_get_timeline_name()
- don't stop adding callbacks if one fails
- remove redundant !! on fence_collection_enable_signaling()
- remove redundant () on fence_collection_signaled
- use fence_default_wait() instead
v4 (chk): Rework, simplification and cleanup:
- Drop FENCE_NO_CONTEXT handling, always allocate a context.
- Rename to fence_array.
- Return fixed driver name.
- Register only one callback at a time.
- Document that create function takes ownership of array.
This looks good to me. Dropping NO_CONTEXT was a good idea, also
registering only one callback makes it looks better.
This will make it even harder to eventually add a real fence_context
structure for tracking and debugging. I know you don't care for amdgpu
since you have amdgpu-specific debug files, and there's some lifetime fun
that makes it not immediately obvious how to resolve it.
Completely independent of my work on amdgpu I still think that it's not
such a good idea to use a complex structure for the fence context.
Especially on SoCs and small embedded systems you probably don't want to
overhead associated with that only for debugging purposes in a
production environment.
But on "lots of
shitty little drivers" systems aka SoCs generic debugging information is
crucial I think. Not liking too much where this is going.
Yeah I agree that generic debugging information is usually crucial, but
the lifetime issues indeed can't be solved without reference counting
and a hole bunch of overhead.
How about V5 of the patch I've just send out? Apart from fixing a few
issues I've made the context and sequence number parameters of the
fence_array object.
This way you don't need to always allocate a new context for each
object, but just enough to keep your timelines straight.
E.g. you don't get a lot of contexts only used once. This is at least
sufficient for my amdgpu use case.
Regards,
Christian.
-Daniel
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