On Wed, 2026-10-21 at 10:42 +0100, Tvrtko Ursulin wrote:
> Another consequence of the recent revert of
> 77a6809f1dc3 ("drm/sched: Remove FIFO and RR and simplify to a single run
> queue")
> is that after the revert we need to adjust entity->rq_priority when
> runtime priority changes are requested.
>
> Only amdgpu does that so the impact is minimal.
> Also considering dynamic
> priority changes are largely broken there, due currently broken entity
> scheduler list handling where the special case of a single scheduler can
> never change it's run-queue. And coupled with the fact for the rest a two-
> tier approach of drm_sched_entity_set_priority() and
> drm_sched_entity_modify_sched() is used, where later directly maps to
> different hardware queue priority by replacing the set of schedulers
> completely.
>
> Hence the regression is limited to rings which have multiple instances
> other than compute and graphics, which would be SDMA only, for which I am
> not sure any userspace actually does dynamic priority changes in the first
> place.
I can't fully grasp what the bug actually is. So is it that we forgot
to adjust the priority in the CFS series, or is it that the partial
revert made this necessary?
>
> Signed-off-by: Tvrtko Ursulin <[email protected]>
> Fixes: 2fa4d8e2c109 ("drm/sched: Add fair scheduling policy")
> Cc: Christian König <[email protected]>
> Cc: Danilo Krummrich <[email protected]>
> Cc: Matthew Brost <[email protected]>
> Cc: Philipp Stanner <[email protected]>
> Cc: <[email protected]> # v7.2+
> ---
> drivers/gpu/drm/scheduler/sched_entity.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c
> b/drivers/gpu/drm/scheduler/sched_entity.c
> index e12709b7bd0c..03e68b4102d5 100644
> --- a/drivers/gpu/drm/scheduler/sched_entity.c
> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> @@ -456,6 +456,8 @@ void drm_sched_entity_set_priority(struct
> drm_sched_entity *entity,
> {
> spin_lock(&entity->lock);
> entity->priority = priority;
> + if (drm_sched_policy != DRM_SCHED_POLICY_FAIR)
> + entity->rq_priority = priority;
> spin_unlock(&entity->lock);
So is there always a bug, or only for FAIR?
> }
> EXPORT_SYMBOL(drm_sched_entity_set_priority);
