On 09/09/2024 09:47, Philipp Stanner wrote:
Hi,
On Fri, 2024-09-06 at 19:06 +0100, Tvrtko Ursulin wrote:
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>
In a recent conversation with Christian there was a thought that
drm_sched_entity_modify_sched() should start using the entity-
rq_lock to be
safe against job submission and simultaneous priority changes.
There are also FIXMEs in gpu_scheduler.h that might be related.
Yes there appears to be a good number of dodgy/unclear areas there.
The kerneldoc accompanying that function however is a bit unclear to
me. For
instance is amdgpu simply doing it wrongly by not serializing the two
in the
driver? Or is the comment referring to some other race condition than
which is
of concern in this series?
To cut the long story short, first three patches try to fix this race
in three
places I *think* can manifest in different ways.
Last patch is a trivial optimisation I spotted can be easily done.
I took a look and at least to me it doesn't appear to be that trivial,
mostly because it takes two locks.
The code does take two locks, but the patch itself does not change any
of that. It just splits the locked helper out so re-locking is avoided.
Would you mind branching that out as a separate patch so that the
series would 100% address bugs?
I wanted to start the series with fixes so backporting will work. If I
put the optimisation first then fixes will not trivially apply to older
kernels. Assuming they are correct of course.
Regards,
Tvrtko
P.
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: Luben Tuikov <ltuikov89@xxxxxxxxx>
Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
Tvrtko Ursulin (4):
drm/sched: Add locking to drm_sched_entity_modify_sched
drm/sched: Always wake up correct scheduler in
drm_sched_entity_push_job
drm/sched: Always increment correct scheduler score
drm/sched: Optimise drm_sched_entity_push_job
drivers/gpu/drm/scheduler/sched_entity.c | 17 ++++++++++++-----
drivers/gpu/drm/scheduler/sched_main.c | 21 ++++++++++++++-------
include/drm/gpu_scheduler.h | 1 +
3 files changed, 27 insertions(+), 12 deletions(-)
