[PATCH 2/9] dma-buf/fence: add fence_is_later()

[Sumit Semwal]

Hi Christian / Alex,


On 29 October 2015 at 21:34, Christian König <deathsimple at vodafone.de> wrote:
> From: Christian König <christian.koenig at amd.com>
>
> Return true when fence 1 is later than fence 2 without
> checking if any of them are signaled.
>
> Useful for driver specific resource handling based on fences.
>
> Signed-off-by: Christian König <christian.koenig at amd.com>
> Reviewed-by: Alex Deucher <alexander.deucher at amd.com>
Please feel free to add my
Acked-by: Sumit Semwal <sumit.semwal at linaro.org>
and take the dma-buf patches via the drm tree, if you'd like.
> ---
>  include/linux/fence.h | 22 +++++++++++++++++++---
>  1 file changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/fence.h b/include/linux/fence.h
> index a4084d6..bb52201 100644
> --- a/include/linux/fence.h
> +++ b/include/linux/fence.h
> @@ -280,6 +280,22 @@ fence_is_signaled(struct fence *fence)
>  }
>
>  /**
> + * fence_is_later - return if f1 is chronologically later than f2
> + * @f1:        [in]    the first fence from the same context
> + * @f2:        [in]    the second fence from the same context
> + *
> + * Returns true if f1 is chronologically later than f2. Both fences must be
> + * from the same context, since a seqno is not re-used across contexts.
> + */
> +static inline bool fence_is_later(struct fence *f1, struct fence *f2)
> +{
> +       if (WARN_ON(f1->context != f2->context))
> +               return false;
> +
> +       return f1->seqno - f2->seqno < INT_MAX;
> +}
> +
> +/**
>   * fence_later - return the chronologically later fence
>   * @f1:        [in]    the first fence from the same context
>   * @f2:        [in]    the second fence from the same context
> @@ -298,10 +314,10 @@ static inline struct fence *fence_later(struct fence *f1, struct fence *f2)
>          * set if enable_signaling wasn't called, and enabling that here is
>          * overkill.
>          */
> -       if (f2->seqno - f1->seqno <= INT_MAX)
> -               return fence_is_signaled(f2) ? NULL : f2;
> -       else
> +       if (fence_is_later(f1, f2))
>                 return fence_is_signaled(f1) ? NULL : f1;
> +       else
> +               return fence_is_signaled(f2) ? NULL : f2;
>  }
>
>  signed long fence_wait_timeout(struct fence *, bool intr, signed long timeout);
> --
> 1.9.1
>
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-- 
Thanks and regards,

Sumit Semwal
Linaro Mobile Group - Kernel Team Lead
Linaro.org │ Open source software for ARM SoCs