On 10/09/2026 08:59, Philipp Stanner wrote:
Changes since v2:
- Fix ordering bug between spsc_queue_pop() and
drm_sched_rq_pop_entity().
Changes since v1:
- Remove a bunch of patches; make this series only about locking
entity->last_scheduled. The rest shall be done in separate patches
and series. Consequently, also do not lock spsc_queue, yet.
- Move lock-cycle patch to first position. (Tvrtko)
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...
Greetings,
Philipp
[1]
https://lore.kernel.org/dri-devel/[email protected]/
[2]
https://lore.kernel.org/dri-devel/[email protected]/
Philipp Stanner (3):
drm/sched: Lock drm_sched_rq_pop_entity() externally
drm/sched: Lock spsc_queue_pop() in drm_sched_entity_pop_job()
FWIW if you could review
https://lore.kernel.org/dri-devel/[email protected]/
you could drop the first two patches from your series. Extra benefit is
that patch fixes a bug and has been tested by the user.
Regards,
Tvrtko
drm/sched: Protect entity->last_scheduled with spinlock
drivers/gpu/drm/scheduler/sched_entity.c | 53 ++++++++++--------------
drivers/gpu/drm/scheduler/sched_rq.c | 4 +-
include/drm/gpu_scheduler.h | 10 ++---
3 files changed, 28 insertions(+), 39 deletions(-)
