[PATCH 0/5] drm/sched: Introduce the miracle of locking to entity

[Philipp Stanner <phasta@kernel.org>]

Both Tvrtko [1] and I [2] have recently proposed some improvals for
drm_sched.

While taking Tvrtko's feedback into account for my patch, I realized
that both his and my patch can be fully replaced with a bigger and far
more beautiful series.

If I am not mistaken, it turns out that the entire entity->entity_idle
completion is also nothing but a workaround around the grave mistake of
not using the greatest helper with parallel programming that exists in
computer science: Locking.

This series adds locking to the last_scheduled field and all checks
related to detect the idleness of the entity. As before, the
job_scheduled event queue causes the periodic checks.

This way, we can get rid of memory barriers, RCU, a few lines of code,
make things more readable, understandable...


Tested with drm-sched-unit tests. I'm a bit busy right now, but wanted
to show you guys the idea. Before merging I'd test it more exhaustively
with Nouveau.

Greetings,
Philipp

[1] https://lore.kernel.org/dri-devel/20260611123423.39819-1-tvrtko.ursulin@igalia.com/
[2] https://lore.kernel.org/dri-devel/20260626081942.2122144-2-phasta@kernel.org/


Philipp Stanner (5):
  drm/sched: Protect entity->last_scheduled with spinlock
  drm/sched: Lock spsc_queue in drm_sched_entity_pop_job()
  drm/sched: Avoid lock cycle for sched_entity
  drm/sched: Lock drm_sched_entity_is_idle()
  drm/sched: Remove entity->entity_idle

 drivers/gpu/drm/scheduler/sched_entity.c | 75 +++++++++++-------------
 drivers/gpu/drm/scheduler/sched_main.c   |  2 -
 drivers/gpu/drm/scheduler/sched_rq.c     |  5 +-
 include/drm/gpu_scheduler.h              | 16 ++---
 4 files changed, 41 insertions(+), 57 deletions(-)


base-commit: be4f10d44757211fd656fa57f37034657f26c883
-- 
2.54.0