Re: [Intel-gfx] [PATCH 4/9] drm/i915: Tidy awaiting on dma-fences

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> Just tidy up the return handling for completed dma-fences. While it may
> return errors for invalid fence, we already know that we have a good
> fence and the only error will be an already signaled fence.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_sw_fence.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_sw_fence.c b/drivers/gpu/drm/i915/i915_sw_fence.c
> index 7daf81f55c90..295b9829e2da 100644
> --- a/drivers/gpu/drm/i915/i915_sw_fence.c
> +++ b/drivers/gpu/drm/i915/i915_sw_fence.c
> @@ -546,13 +546,11 @@ int __i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
>  	cb->fence = fence;
>  	i915_sw_fence_await(fence);
>  
> -	ret = dma_fence_add_callback(dma, &cb->base, __dma_i915_sw_fence_wake);
> -	if (ret == 0) {
> -		ret = 1;
> -	} else {
> +	ret = 1;
> +	if (dma_fence_add_callback(dma, &cb->base, __dma_i915_sw_fence_wake)) {
> +		/* fence already signaled */

This seems to hold water now. Perhaps for eternity.

But how about if (dma_fence_add_callback() == -ENOENT) ret = 0; else
GEM_BUG_ON()?
-Mika

>  		__dma_i915_sw_fence_wake(dma, &cb->base);
> -		if (ret == -ENOENT) /* fence already signaled */
> -			ret = 0;
> +		ret = 0;
>  	}
>  
>  	return ret;
> -- 
> 2.20.1
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