[PATCH v5] dma-fence: Propagate errors to dma-fence-array container

[Koenig, Christian]

Am 11.08.19 um 18:25 schrieb Chris Wilson:
> When one of the array of fences is signaled, propagate its errors to the
> parent fence-array (keeping the first error to be raised).
>
> v2: Opencode cmpxchg_local to avoid compiler freakout.
> v3: Be careful not to flag an error if we race against signal-on-any.
> v4: Same applies to installing the signal cb.
> v5: Use cmpxchg to only set the error once before using a nifty idea by
> Christian to avoid changing the status after emitting the signal.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Sumit Semwal <sumit.semwal at linaro.org>
> Cc: Gustavo Padovan <gustavo at padovan.org>
> Cc: Christian König <christian.koenig at amd.com>

Reviewed-by: Christian König <christian.koenig at amd.com>

> ---
>   drivers/dma-buf/dma-fence-array.c | 32 ++++++++++++++++++++++++++++++-
>   1 file changed, 31 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c
> index 12c6f64c0bc2..d3fbd950be94 100644
> --- a/drivers/dma-buf/dma-fence-array.c
> +++ b/drivers/dma-buf/dma-fence-array.c
> @@ -13,6 +13,8 @@
>   #include <linux/slab.h>
>   #include <linux/dma-fence-array.h>
>   
> +#define PENDING_ERROR 1
> +
>   static const char *dma_fence_array_get_driver_name(struct dma_fence *fence)
>   {
>   	return "dma_fence_array";
> @@ -23,10 +25,29 @@ static const char *dma_fence_array_get_timeline_name(struct dma_fence *fence)
>   	return "unbound";
>   }
>   
> +static void dma_fence_array_set_pending_error(struct dma_fence_array *array,
> +					      int error)
> +{
> +	/*
> +	 * Propagate the first error reported by any of our fences, but only
> +	 * before we ourselves are signaled.
> +	 */
> +	if (error)
> +		cmpxchg(&array->base.error, PENDING_ERROR, error);
> +}
> +
> +static void dma_fence_array_clear_pending_error(struct dma_fence_array *array)
> +{
> +	/* Clear the error flag if not actually set. */
> +	cmpxchg(&array->base.error, PENDING_ERROR, 0);
> +}
> +
>   static void irq_dma_fence_array_work(struct irq_work *wrk)
>   {
>   	struct dma_fence_array *array = container_of(wrk, typeof(*array), work);
>   
> +	dma_fence_array_clear_pending_error(array);
> +
>   	dma_fence_signal(&array->base);
>   	dma_fence_put(&array->base);
>   }
> @@ -38,6 +59,8 @@ static void dma_fence_array_cb_func(struct dma_fence *f,
>   		container_of(cb, struct dma_fence_array_cb, cb);
>   	struct dma_fence_array *array = array_cb->array;
>   
> +	dma_fence_array_set_pending_error(array, f->error);
> +
>   	if (atomic_dec_and_test(&array->num_pending))
>   		irq_work_queue(&array->work);
>   	else
> @@ -63,9 +86,14 @@ static bool dma_fence_array_enable_signaling(struct dma_fence *fence)
>   		dma_fence_get(&array->base);
>   		if (dma_fence_add_callback(array->fences[i], &cb[i].cb,
>   					   dma_fence_array_cb_func)) {
> +			int error = array->fences[i]->error;
> +
> +			dma_fence_array_set_pending_error(array, error);
>   			dma_fence_put(&array->base);
> -			if (atomic_dec_and_test(&array->num_pending))
> +			if (atomic_dec_and_test(&array->num_pending)) {
> +				dma_fence_array_clear_pending_error(array);
>   				return false;
> +			}
>   		}
>   	}
>   
> @@ -142,6 +170,8 @@ struct dma_fence_array *dma_fence_array_create(int num_fences,
>   	atomic_set(&array->num_pending, signal_on_any ? 1 : num_fences);
>   	array->fences = fences;
>   
> +	array->base.error = PENDING_ERROR;
> +
>   	return array;
>   }
>   EXPORT_SYMBOL(dma_fence_array_create);