Re: [Linaro-mm-sig] [PATCH] dma-buf: make returning the exclusive fence optional

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Jan 10, 2018 at 01:53:41PM +0100, Christian König wrote:
> Change reservation_object_get_fences_rcu to make the exclusive fence
> pointer optional.
> 
> If not specified the exclusive fence is put into the fence array as
> well.
> 
> This is helpful for a couple of cases where we need all fences in a
> single array.
> 
> Signed-off-by: Christian König <christian.koenig@amd.com>

Seeing the use-case for this would be a lot more interesting ...
-Daniel

> ---
>  drivers/dma-buf/reservation.c | 31 ++++++++++++++++++++++---------
>  1 file changed, 22 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
> index b759a569b7b8..461afa9febd4 100644
> --- a/drivers/dma-buf/reservation.c
> +++ b/drivers/dma-buf/reservation.c
> @@ -374,8 +374,9 @@ EXPORT_SYMBOL(reservation_object_copy_fences);
>   * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
>   * the required size, and must be freed by caller)
>   *
> - * RETURNS
> - * Zero or -errno
> + * Retrieve all fences from the reservation object. If the pointer for the
> + * exclusive fence is not specified the fence is put into the array of the
> + * shared fences as well. Returns either zero or -ENOMEM.
>   */
>  int reservation_object_get_fences_rcu(struct reservation_object *obj,
>  				      struct dma_fence **pfence_excl,
> @@ -389,8 +390,8 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj,
>  
>  	do {
>  		struct reservation_object_list *fobj;
> -		unsigned seq;
> -		unsigned int i;
> +		unsigned int i, seq;
> +		size_t sz = 0;
>  
>  		shared_count = i = 0;
>  
> @@ -402,9 +403,14 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj,
>  			goto unlock;
>  
>  		fobj = rcu_dereference(obj->fence);
> -		if (fobj) {
> +		if (fobj)
> +			sz += sizeof(*shared) * fobj->shared_max;
> +
> +		if (!pfence_excl && fence_excl)
> +			sz += sizeof(*shared);
> +
> +		if (sz) {
>  			struct dma_fence **nshared;
> -			size_t sz = sizeof(*shared) * fobj->shared_max;
>  
>  			nshared = krealloc(shared, sz,
>  					   GFP_NOWAIT | __GFP_NOWARN);
> @@ -420,13 +426,19 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj,
>  				break;
>  			}
>  			shared = nshared;
> -			shared_count = fobj->shared_count;
> -
> +			shared_count = fobj ? fobj->shared_count : 0;
>  			for (i = 0; i < shared_count; ++i) {
>  				shared[i] = rcu_dereference(fobj->shared[i]);
>  				if (!dma_fence_get_rcu(shared[i]))
>  					break;
>  			}
> +
> +			if (!pfence_excl && fence_excl) {
> +				shared[i] = fence_excl;
> +				fence_excl = NULL;
> +				++i;
> +				++shared_count;
> +			}
>  		}
>  
>  		if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
> @@ -448,7 +460,8 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj,
>  
>  	*pshared_count = shared_count;
>  	*pshared = shared;
> -	*pfence_excl = fence_excl;
> +	if (pfence_excl)
> +		*pfence_excl = fence_excl;
>  
>  	return ret;
>  }
> -- 
> 2.14.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch