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

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Date:   Wed, 8 Sep 2021 11:19:15 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Rob Clark <robdclark@...il.com>,
        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>
Cc:     Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH v3 7/9] dma-buf/fence-chain: Add fence deadline support

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

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