[PATCH 0/9] drm/syncobj: Add full-featured wait support (v2)

[Jason Ekstrand]

On Wed, Aug 16, 2017 at 1:10 PM, Jason Ekstrand <jason at jlekstrand.net>
wrote:

> On Wed, Aug 16, 2017 at 9:53 AM, Christian König <christian.koenig at amd.com
> > wrote:
>
>> [SNIP]
>>
>>> See a wait_queue is a callback mechanism anyway, so you are wrapping a
>>>> callback mechanism inside another callback mechanism and that makes not
>>>> really much sense.
>>>>
>>>
>>> Fair enough.  There is one little snag though:  We need to wait on sync
>>> objects and fences at the same time in order for WAIT_ANY | WAIT_FOR_SUBMIT
>>> to work.  I see two options here:
>>>
>>>  1) Convert dma-fence to use waitqueue instead of its callback mechanism
>>> and add a wait_queue_any.  A quick grep for dma_fence_add_callback says
>>> that this would affect four drivers.
>>>
>>
>> The more I think about it, the less sense using waitqueues makes.  The
>> fundamental problem here is that the event we are waiting on is actually
>> the concatenation of two events: submit and signal.  Since we are waiting
>> on several of these pairs of concatenated events simultaneously, the only
>> two options we have are to either combine them into one event (the proxy
>> approach) or to implement a wait which is capable of handling both at the
>> same time.  I don't see a way to do the latter with wait queues.
>>
>>
>> Agree completely.
>>
>> Essentially we would need to enable wait_event_* to wait for multiple
>> events and then convert all the fence callback stuff to wait_event
>> structures.
>>
>> But that is certainly outside the scope of this patchset, so feel free to
>> go ahead with the approach of waiting manually (but please without the
>> bugs).
>>
>
> Well, the patches I sent last night should do just that.  It's mostly the
> original approach but with the bugfixes from versions 3 and 4.  Modulo
> finding additional bugs, I think they should be good to go.
>

ping?
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