Re: [Intel-gfx] [PATCH 5/6] RFC: dma-buf: Add an extra fence to dma_resv_get_singleton_unlocked

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, May 24, 2021 at 03:59:53PM -0500, Jason Ekstrand wrote:
> For dma-buf sync_file import, we want to get all the fences on a
> dma_resv plus one more.  We could wrap the fence we get back in an array
> fence or we could make dma_resv_get_singleton_unlocked take "one more"
> to make this case easier.
> 
> Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>

Ah now it makes very obviously sense.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  drivers/dma-buf/dma-buf.c  |  2 +-
>  drivers/dma-buf/dma-resv.c | 23 +++++++++++++++++++++--
>  include/linux/dma-resv.h   |  3 ++-
>  3 files changed, 24 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index 86efe71c0db96..f23d939e0e833 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -386,7 +386,7 @@ static long dma_buf_export_sync_file(struct dma_buf *dmabuf,
>  		return fd;
>  
>  	if (arg.flags & DMA_BUF_SYNC_WRITE) {
> -		fence = dma_resv_get_singleton_unlocked(dmabuf->resv);
> +		fence = dma_resv_get_singleton_unlocked(dmabuf->resv, NULL);
>  		if (IS_ERR(fence)) {
>  			ret = PTR_ERR(fence);
>  			goto err_put_fd;
> diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
> index 312a3a59dac6a..3c0ef8d0f599b 100644
> --- a/drivers/dma-buf/dma-resv.c
> +++ b/drivers/dma-buf/dma-resv.c
> @@ -527,6 +527,7 @@ EXPORT_SYMBOL_GPL(dma_resv_get_fences_unlocked);
>  /**
>   * dma_resv_get_singleton_unlocked - get a single fence for the dma_resv object
>   * @obj: the reservation object
> + * @extra: extra fence to add to the resulting array
>   * @result: resulting dma_fence
>   *
>   * Get a single fence representing all unsignaled fences in the dma_resv object
> @@ -536,7 +537,8 @@ EXPORT_SYMBOL_GPL(dma_resv_get_fences_unlocked);
>   * RETURNS
>   * Returns -NOMEM if allocations fail, zero otherwise.
>   */
> -struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj)
> +struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj,
> +						  struct dma_fence *extra)
>  {
>  	struct dma_fence *result, **resv_fences, *fence, *chain, **fences;
>  	struct dma_fence_array *array;
> @@ -547,7 +549,7 @@ struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj)
>  	if (err)
>  		return ERR_PTR(err);
>  
> -	if (num_resv_fences == 0)
> +	if (num_resv_fences == 0 && !extra)
>  		return NULL;
>  
>  	num_fences = 0;
> @@ -563,6 +565,16 @@ struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj)
>  		}
>  	}
>  
> +	if (extra) {
> +		dma_fence_deep_dive_for_each(fence, chain, j, extra) {
> +			if (dma_fence_is_signaled(fence))
> +				continue;
> +
> +			result = fence;
> +			++num_fences;
> +		}
> +	}
> +
>  	if (num_fences <= 1) {
>  		result = dma_fence_get(result);
>  		goto put_resv_fences;
> @@ -583,6 +595,13 @@ struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj)
>  		}
>  	}
>  
> +	if (extra) {
> +		dma_fence_deep_dive_for_each(fence, chain, j, extra) {
> +			if (dma_fence_is_signaled(fence))
> +				fences[num_fences++] = dma_fence_get(fence);
> +		}
> +	}
> +
>  	if (num_fences <= 1) {
>  		result = num_fences ? fences[0] : NULL;
>  		kfree(fences);
> diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
> index c529ccee94bc5..156d989e95ab4 100644
> --- a/include/linux/dma-resv.h
> +++ b/include/linux/dma-resv.h
> @@ -285,7 +285,8 @@ int dma_resv_get_fences_unlocked(struct dma_resv *obj,
>  
>  int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src);
>  
> -struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj);
> +struct dma_fence *dma_resv_get_singleton_unlocked(struct dma_resv *obj,
> +						  struct dma_fence *extra);
>  
>  long dma_resv_wait_timeout_unlocked(struct dma_resv *obj, bool wait_all, bool intr,
>  				    unsigned long timeout);
> -- 
> 2.31.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch