Re: [PATCH v3 7/9] dma-buf/fence-chain: Add fence deadline support

[Christian König]

Am 08.09.21 um 20:45 schrieb Daniel Vetter:
> On Wed, Sep 08, 2021 at 11:19:15AM -0700, Rob Clark wrote:
> > On Wed, Sep 8, 2021 at 10:54 AM Daniel Vetter <daniel@xxxxxxxx> wrote:
> > > On Fri, Sep 03, 2021 at 11:47:58AM -0700, Rob Clark wrote:
> > > > From: Rob Clark <robdclark@xxxxxxxxxxxx>
> > > >
> > > > Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> > > > ---
> > > >   drivers/dma-buf/dma-fence-chain.c | 13 +++++++++++++
> > > >   1 file changed, 13 insertions(+)
> > > >
> > > > diff --git a/drivers/dma-buf/dma-fence-chain.c b/drivers/dma-buf/dma-fence-chain.c
> > > > index 1b4cb3e5cec9..736a9ad3ea6d 100644
> > > > --- a/drivers/dma-buf/dma-fence-chain.c
> > > > +++ b/drivers/dma-buf/dma-fence-chain.c
> > > > @@ -208,6 +208,18 @@ static void dma_fence_chain_release(struct dma_fence *fence)
> > > >        dma_fence_free(fence);
> > > >   }
> > > >
> > > > +
> > > > +static void dma_fence_chain_set_deadline(struct dma_fence *fence,
> > > > +                                      ktime_t deadline)
> > > > +{
> > > > +     dma_fence_chain_for_each(fence, fence) {
> > > > +             struct dma_fence_chain *chain = to_dma_fence_chain(fence);
> > > > +             struct dma_fence *f = chain ? chain->fence : fence;
> > > Doesn't this just end up calling set_deadline on a chain, potenetially
> > > resulting in recursion? Also I don't think this should ever happen, why
> > > did you add that?
> > Tbh the fence-chain was the part I was a bit fuzzy about, and the main
> > reason I added igt tests.  The iteration is similar to how, for ex,
> > dma_fence_chain_signaled() work, and according to the igt test it does
> > what was intended
> Huh indeed. Maybe something we should fix, like why does the
> dma_fence_chain_for_each not give you the upcast chain pointer ... I guess
> this also needs more Christian and less me.

Yeah I was also already thinking about having a 
dma_fence_chain_for_each_contained() macro which directly returns the 
containing fence, just didn't had time to implement/clean that up.

And yes the patch is correct as it is and avoid the recursion, so 
Reviewed-by: Christian König <christian.koenig@xxxxxxx> for this one.

Regards,
Christian.

> -Daniel
>
> > BR,
> > -R
> >
> > > -Daniel
> > >
> > > > +
> > > > +             dma_fence_set_deadline(f, deadline);
> > > > +     }
> > > > +}
> > > > +
> > > >   const struct dma_fence_ops dma_fence_chain_ops = {
> > > >        .use_64bit_seqno = true,
> > > >        .get_driver_name = dma_fence_chain_get_driver_name,
> > > > @@ -215,6 +227,7 @@ const struct dma_fence_ops dma_fence_chain_ops = {
> > > >        .enable_signaling = dma_fence_chain_enable_signaling,
> > > >        .signaled = dma_fence_chain_signaled,
> > > >        .release = dma_fence_chain_release,
> > > > +     .set_deadline = dma_fence_chain_set_deadline,
> > > >   };
> > > >   EXPORT_SYMBOL(dma_fence_chain_ops);
> > > >
> > > > --
> > > > 2.31.1
> > > --
> > > Daniel Vetter
> > > Software Engineer, Intel Corporation
> > > http://blog.ffwll.ch