Re: [PATCH 2/2] drm/sched: fix dropping the last fence ref

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Nov 16, 2021 at 10:25:19AM +0100, Christian König wrote:
> We need to grab another ref before trying to add the fence to the sched
> job and not after.
> 
> Signed-off-by: Christian König <christian.koenig@amd.com>

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

I wondered first why this goes boom, but then I realized that in some
cases add_dependency() drops the reference of the passed-in fence.

Please also add the Fixes: line like in the previous patch.

Cheers, Daniel

> ---
>  drivers/gpu/drm/scheduler/sched_main.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index 94fe51b3caa2..400d201c3c28 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -704,12 +704,14 @@ int drm_sched_job_add_implicit_dependencies(struct drm_sched_job *job,
>  	int ret;
>  
>  	dma_resv_for_each_fence(&cursor, obj->resv, write, fence) {
> -		ret = drm_sched_job_add_dependency(job, fence);
> -		if (ret)
> -			return ret;
> -
>  		/* Make sure to grab an additional ref on the added fence */
>  		dma_fence_get(fence);
> +
> +		ret = drm_sched_job_add_dependency(job, fence);
> +		if (ret) {
> +			dma_fence_put(fence);
> +			return ret;
> +		}
>  	}
>  	return 0;
>  }
> -- 
> 2.25.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch