linux-kernel - Re: [PATCH 1/2] dma-buf/fence: add fence

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Date:	Thu, 19 May 2016 10:20:07 -0300
From:	Gustavo Padovan <gustavo.padovan@...labora.co.uk>
To:	Christian König <christian.koenig@....com>
Cc:	Chris Wilson <chris@...is-wilson.co.uk>,
	Gustavo Padovan <gustavo@...ovan.org>,
	dri-devel@...ts.freedesktop.org, marcheu@...gle.com,
	Daniel Stone <daniels@...labora.com>, seanpaul@...gle.com,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	linux-kernel@...r.kernel.org, laurent.pinchart@...asonboard.com,
	Alex Deucher <alexander.deucher@....com>,
	John Harrison <John.C.Harrison@...el.com>, m.chehab@...sung.com
Subject: Re: [PATCH 1/2] dma-buf/fence: add fence_collection fences

Hi Christian,

2016-05-19 Christian König <christian.koenig@....com>:

> Am 19.05.2016 um 00:57 schrieb Chris Wilson:
> > On Wed, May 18, 2016 at 05:59:52PM -0300, Gustavo Padovan wrote:
> > > +static void collection_check_cb_func(struct fence *fence, struct fence_cb *cb)
> > > +{
> > > +	struct fence_collection_cb *f_cb;
> > > +	struct fence_collection *collection;
> > > +
> > > +	f_cb = container_of(cb, struct fence_collection_cb, cb);
> > > +	collection = f_cb->collection;
> > > +
> > > +	if (atomic_dec_and_test(&collection->num_pending_fences))
> > > +		fence_signal(&collection->base);
> > > +}
> > > +
> > > +static bool fence_collection_enable_signaling(struct fence *fence)
> > > +{
> > > +	struct fence_collection *collection = to_fence_collection(fence);
> > > +	int i;
> > > +
> > > +	for (i = 0 ; i < collection->num_fences ; i++) {
> > > +		if (fence_add_callback(collection->fences[i].fence,
> > > +				       &collection->fences[i].cb,
> > > +				       collection_check_cb_func)) {
> > > +			atomic_dec(&collection->num_pending_fences);
> > > +		}
> > > +	}
> > We don't always have a convenient means to preallocate an array of
> > fences to use. Keeping a list of fences in addition to the array would
> > be easier to user in many circumstances.
> 
> I agree that there is use for such an implementation as well, but as
> mentioned in the last review cycle we intentionally chose an array instead
> of a more complex implementation here.
> 
> This way the array can be passed to function like fence_wait_any_timeout()
> as well.
> 
> I also suggested to rename it to fence_array to make that difference clear
> and allow for another implementation to live side by side with this.
> 
> My crux at the moment is that I need both for the amdgpu driver, an array
> based implementation and a collection like one.
> 
> Gustavo would you mind if I take your patches and work a bit on this?

Please go ahead with this and let me know if you need anything from me.

	Gustavo