[PATCH 2/2] dma-buf: try to replace a signaled fence in reservation_object_add_shared_inplace

[Chris Wilson]

Quoting Christian König (2017-10-30 14:59:04)
> From: Christian König <christian.koenig at amd.com>
> 
> The amdgpu issue to also need signaled fences in the reservation objects should
> be fixed by now.
> 
> Optimize the handling by replacing a signaled fence when adding a new
> shared one.
> 
> Signed-off-by: Christian König <christian.koenig at amd.com>
> ---
>  drivers/dma-buf/reservation.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
> index 6fc794576997..a3928ce9f311 100644
> --- a/drivers/dma-buf/reservation.c
> +++ b/drivers/dma-buf/reservation.c
> @@ -104,7 +104,8 @@ reservation_object_add_shared_inplace(struct reservation_object *obj,
>                                       struct reservation_object_list *fobj,
>                                       struct dma_fence *fence)
>  {
> -       u32 i;
> +       struct dma_fence *signaled = NULL;
> +       u32 i, signaled_idx;
>  
>         dma_fence_get(fence);
>  
> @@ -126,17 +127,28 @@ reservation_object_add_shared_inplace(struct reservation_object *obj,
>                         dma_fence_put(old_fence);
>                         return;
>                 }
> +
> +               if (!signaled && dma_fence_is_signaled(old_fence)) {
> +                       signaled = old_fence;
> +                       signaled_idx = i;
> +               }

How much do we care about only keeping one fence per-ctx here? You could
rearrange this to break on old_fence->context == fence->context ||
dma_fence_is_signaled(old_fence) then everyone can use the final block.
-Chris