[PATCH 2/8] drm/sched: Always wake up correct scheduler in drm_sched_entity_push_job

[Tvrtko Ursulin]

On 24/09/2024 15:20, Christian König wrote:
> Am 24.09.24 um 16:12 schrieb Tvrtko Ursulin:
>>
>> On 24/09/2024 14:55, Christian König wrote:
>>> I've pushed the first to drm-misc-next, but that one here fails to 
>>> apply cleanly.
>>
>> This appears due 440d52b370b0 ("drm/sched: Fix dynamic job-flow 
>> control race") in drm-misc-fixes.
>>
>> In theory 1-3 from my series are fixes. Should they also go to 
>> drm-misc-fixes? I am not too familiar with the drm-misc flow.
> 
> Ah shit, in that case you should have spitted the patches up into fixes 
> and next. Going to push the first 3 to fixes.

Sorry my drm-intel ways of thinking (cherry picked fixes) are hard to 
get rid of. Hence the series was structured as 1-3 fixes, 4-8 refactors etc.

Now appears it is too late to pull out the first one from drm-misc-next.
>> Or the series now needs to wait for some backmerge?
> 
> Are the remaining 3 patches independent? If not then we need to wait for 
> a backmerge.

These are independent:

Fixes:

  1/8 "drm/sched: Add locking to drm_sched_entity_modify_sched"

Not fixes:

  5/8 "drm/sched: Stop setting current entity in FIFO mode"
  6/8 "drm/sched: Re-order struct drm_sched_rq members for clarity"

While the rest touch at least some common areas.

2/8 and 3/8 are also fixes.

4/8, 7/8 and 8/8 not fixes but depend on 2/8 and 3/8.

Regards,

Tvrtko

>>> Am 24.09.24 um 12:19 schrieb Tvrtko Ursulin:
>>>> From: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
>>>>
>>>> Since drm_sched_entity_modify_sched() can modify the entities run 
>>>> queue,
>>>> lets make sure to only dereference the pointer once so both adding and
>>>> waking up are guaranteed to be consistent.
>>>>
>>>> Alternative of moving the spin_unlock to after the wake up would for 
>>>> now
>>>> be more problematic since the same lock is taken inside
>>>> drm_sched_rq_update_fifo().
>>>>
>>>> v2:
>>>>   * Improve commit message. (Philipp)
>>>>   * Cache the scheduler pointer directly. (Christian)
>>>>
>>>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
>>>> Fixes: b37aced31eb0 ("drm/scheduler: implement a function to modify 
>>>> sched list")
>>>> Cc: Christian König <christian.koenig at amd.com>
>>>> Cc: Alex Deucher <alexander.deucher at amd.com>
>>>> Cc: Luben Tuikov <ltuikov89 at gmail.com>
>>>> Cc: Matthew Brost <matthew.brost at intel.com>
>>>> Cc: David Airlie <airlied at gmail.com>
>>>> Cc: Daniel Vetter <daniel at ffwll.ch>
>>>> Cc: Philipp Stanner <pstanner at redhat.com>
>>>> Cc: dri-devel at lists.freedesktop.org
>>>> Cc: <stable at vger.kernel.org> # v5.7+
>>>> Reviewed-by: Christian König <christian.koenig at amd.com>
>>>> ---
>>>>   drivers/gpu/drm/scheduler/sched_entity.c | 10 ++++++++--
>>>>   1 file changed, 8 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c 
>>>> b/drivers/gpu/drm/scheduler/sched_entity.c
>>>> index 0e002c17fcb6..a75eede8bf8d 100644
>>>> --- a/drivers/gpu/drm/scheduler/sched_entity.c
>>>> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
>>>> @@ -599,6 +599,9 @@ void drm_sched_entity_push_job(struct 
>>>> drm_sched_job *sched_job)
>>>>       /* first job wakes up scheduler */
>>>>       if (first) {
>>>> +        struct drm_gpu_scheduler *sched;
>>>> +        struct drm_sched_rq *rq;
>>>> +
>>>>           /* Add the entity to the run queue */
>>>>           spin_lock(&entity->rq_lock);
>>>>           if (entity->stopped) {
>>>> @@ -608,13 +611,16 @@ void drm_sched_entity_push_job(struct 
>>>> drm_sched_job *sched_job)
>>>>               return;
>>>>           }
>>>> -        drm_sched_rq_add_entity(entity->rq, entity);
>>>> +        rq = entity->rq;
>>>> +        sched = rq->sched;
>>>> +
>>>> +        drm_sched_rq_add_entity(rq, entity);
>>>>           spin_unlock(&entity->rq_lock);
>>>>           if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
>>>>               drm_sched_rq_update_fifo(entity, submit_ts);
>>>> -        drm_sched_wakeup(entity->rq->sched);
>>>> +        drm_sched_wakeup(sched);
>>>>       }
>>>>   }
>>>>   EXPORT_SYMBOL(drm_sched_entity_push_job);
>>>
>