On Thu, 2025-10-23 at 14:34 +0200, Philipp Stanner wrote:
> The assembled developers agreed at the X.Org Developers Conference 2025
> that the hack added for amdgpu in drm_sched_fini() shall be removed. It
> shouldn't be needed by amdgpu anymore.
>
> As it's unclear whether all drivers really follow the life time rule of
> entities having to be torn down before their scheduler, it is reasonable
> to warn for a while before removing the hack.
>
> Add a warning in drm_sched_fini() that fires if an entity is still
> active.
>
> Signed-off-by: Philipp Stanner <[email protected]>
Can someone review this?
At XDC we agreed on removing the hack, but wanted to add a warning
print first for a few releases, to really catch if there are no users
anymore.
Thx
P.
> ---
> Changes in v3:
> - Add a READ_ONCE() + comment to make the warning slightly less
> horrible.
>
> Changes in v2:
> - Fix broken brackets.
> ---
> drivers/gpu/drm/scheduler/sched_main.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c
> b/drivers/gpu/drm/scheduler/sched_main.c
> index 46119aacb809..31039b08c7b9 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -1419,7 +1419,7 @@ void drm_sched_fini(struct drm_gpu_scheduler *sched)
> struct drm_sched_rq *rq = sched->sched_rq[i];
>
> spin_lock(&rq->lock);
> - list_for_each_entry(s_entity, &rq->entities, list)
> + list_for_each_entry(s_entity, &rq->entities, list) {
> /*
> * Prevents reinsertion and marks job_queue as idle,
> * it will be removed from the rq in
> drm_sched_entity_fini()
> @@ -1440,8 +1440,15 @@ void drm_sched_fini(struct drm_gpu_scheduler *sched)
> * For now, this remains a potential race in all
> * drivers that keep entities alive for longer than
> * the scheduler.
> + *
> + * The READ_ONCE() is there to make the lockless read
> + * (warning about the lockless write below) slightly
> + * less broken...
> */
> + if (!READ_ONCE(s_entity->stopped))
> + dev_warn(sched->dev, "Tearing down scheduler
> with active entities!\n");
> s_entity->stopped = true;
> + }
> spin_unlock(&rq->lock);
> kfree(sched->sched_rq[i]);
> }
