On 2/13/19 1:58 PM, Andrey Grodzovsky wrote:
> When ring hang happens amdgpu_dm_commit_planes during flip is holding
> the BO reserved and then stack waiting for fences to signal in
> reservation_object_wait_timeout_rcu (which won't signal because there
> was a hnag). Then when we try to shutdown display block during reset
> recovery from drm_atomic_helper_suspend we also try to reserve the BO
> from dm_plane_helper_cleanup_fb ending in deadlock.
> Also remove useless WARN_ON
>
> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
> ---
> 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 acc4ff8..f8dec36 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -4802,14 +4802,21 @@ 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);
>
>
Is it safe that we're just continuing like this? It's probably better to
just unreserve the buffer and continue to the next plane, no?
Nicholas Kazlauskas
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