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

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

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

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@amd.com> 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