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

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Date:   Wed, 8 Sep 2021 20:45:27 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Rob Clark <robdclark@...il.com>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@...ts.linaro.org>,
        Christian König 
        <ckoenig.leichtzumerken@...il.com>,
        Michel Dänzer <michel@...nzer.net>,
        Pekka Paalanen <ppaalanen@...il.com>,
        Rob Clark <robdclark@...omium.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Christian König <christian.koenig@....com>,
        "open list:SYNC FILE FRAMEWORK" <linux-media@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH v3 7/9] dma-buf/fence-chain: Add fence deadline support

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@...ll.ch> wrote:
> >
> > On Fri, Sep 03, 2021 at 11:47:58AM -0700, Rob Clark wrote:
> > > From: Rob Clark <robdclark@...omium.org>
> > >
> > > Signed-off-by: Rob Clark <robdclark@...omium.org>
> > > ---
> > >  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.
-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

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch