[PATCH 4/4] drm/amd/display: Restore deleted patch to resolve reset deadlock.

[Kazlauskas, Nicholas]

On 4/11/19 12:03 PM, Andrey Grodzovsky wrote:
> Patch '5edb0c9b Fix deadlock with display during hanged ring recovery'
> was accidentaly removed during one of DALs code merges.
> 
> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky at amd.com>

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>

Probably got lost in a refactor.

Also, didn't Christian have a patch recently to not lock the reservation 
object when waiting for the fence? Looks like that's missing too, or 
maybe it didn't get merged.

Nicholas Kazlauskas

> ---
>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 19 +++++++++++++------
>   1 file changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 0648794..27e0383 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -5138,14 +5138,21 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
>   		 */
>   		abo = gem_to_amdgpu_bo(fb->obj[0]);
>   		r = amdgpu_bo_reserve(abo, true);
> -		if (unlikely(r != 0)) {
> +		if (unlikely(r != 0))
>   			DRM_ERROR("failed to reserve buffer before flip\n");
> -			WARN_ON(1);
> -		}
>   
> -		/* Wait for all fences on this FB */
> -		WARN_ON(reservation_object_wait_timeout_rcu(abo->tbo.resv, true, false,
> -									    MAX_SCHEDULE_TIMEOUT) < 0);
> +		/*
> +		 * Wait for all fences on this FB. Do limited wait to avoid
> +		 * deadlock during GPU reset when this fence will not signal
> +		 * but we hold reservation lock for the BO.
> +		 */
> +		r = reservation_object_wait_timeout_rcu(abo->tbo.resv,
> +							true, false,
> +							msecs_to_jiffies(5000));
> +		if (unlikely(r == 0))
> +			DRM_ERROR("Waiting for fences timed out.");
> +
> +
>   
>   		amdgpu_bo_get_tiling_flags(abo, &tiling_flags);
>   
>