[PATCH v3 2/5] drm/sched/tests: Port tests to new cleanup method
Tvrtko Ursulin
tvrtko.ursulin at igalia.com
Fri May 23 15:49:57 UTC 2025
On 22/05/2025 15:59, Philipp Stanner wrote:
> On Thu, 2025-05-22 at 15:06 +0100, Tvrtko Ursulin wrote:
>>
>> On 22/05/2025 09:27, Philipp Stanner wrote:
>>> The drm_gpu_scheduler now supports a callback to help
>>> drm_sched_fini()
>>> avoid memory leaks. This callback instructs the driver to signal
>>> all
>>> pending hardware fences.
>>>
>>> Implement the new callback
>>> drm_sched_backend_ops.cancel_pending_fences().
>>>
>>> Have the callback use drm_mock_sched_job_complete() with a new
>>> error
>>> field for the fence error.
>>>
>>> Keep the job status as DRM_MOCK_SCHED_JOB_DONE for now, since there
>>> is
>>> no party for which checking for a CANCELED status would be useful
>>> currently.
>>>
>>> Signed-off-by: Philipp Stanner <phasta at kernel.org>
>>> ---
>>> .../gpu/drm/scheduler/tests/mock_scheduler.c | 67 +++++++-------
>>> -----
>>> drivers/gpu/drm/scheduler/tests/sched_tests.h | 4 +-
>>> 2 files changed, 25 insertions(+), 46 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/scheduler/tests/mock_scheduler.c
>>> b/drivers/gpu/drm/scheduler/tests/mock_scheduler.c
>>> index f999c8859cf7..eca47f0395bc 100644
>>> --- a/drivers/gpu/drm/scheduler/tests/mock_scheduler.c
>>> +++ b/drivers/gpu/drm/scheduler/tests/mock_scheduler.c
>>> @@ -55,7 +55,7 @@ void drm_mock_sched_entity_free(struct
>>> drm_mock_sched_entity *entity)
>>> drm_sched_entity_destroy(&entity->base);
>>> }
>>>
>>> -static void drm_mock_sched_job_complete(struct drm_mock_sched_job
>>> *job)
>>> +static void drm_mock_sched_job_complete(struct drm_mock_sched_job
>>> *job, int err)
>>> {
>>> struct drm_mock_scheduler *sched =
>>> drm_sched_to_mock_sched(job->base.sched);
>>> @@ -63,7 +63,9 @@ static void drm_mock_sched_job_complete(struct
>>> drm_mock_sched_job *job)
>>> lockdep_assert_held(&sched->lock);
>>>
>>> job->flags |= DRM_MOCK_SCHED_JOB_DONE;
>>> - list_move_tail(&job->link, &sched->done_list);
>>> + list_del(&job->link);
>>> + if (err)
>>> + dma_fence_set_error(&job->hw_fence, err);
>>> dma_fence_signal(&job->hw_fence);
>>> complete(&job->done);
>>> }
>>> @@ -89,7 +91,7 @@ drm_mock_sched_job_signal_timer(struct hrtimer
>>> *hrtimer)
>>> break;
>>>
>>> sched->hw_timeline.cur_seqno = job-
>>>> hw_fence.seqno;
>>> - drm_mock_sched_job_complete(job);
>>> + drm_mock_sched_job_complete(job, 0);
>>> }
>>> spin_unlock_irqrestore(&sched->lock, flags);
>>>
>>> @@ -212,26 +214,33 @@ mock_sched_timedout_job(struct drm_sched_job
>>> *sched_job)
>>>
>>> static void mock_sched_free_job(struct drm_sched_job *sched_job)
>>> {
>>> - struct drm_mock_scheduler *sched =
>>> - drm_sched_to_mock_sched(sched_job->sched);
>>> struct drm_mock_sched_job *job =
>>> drm_sched_job_to_mock_job(sched_job);
>>> - unsigned long flags;
>>>
>>> - /* Remove from the scheduler done list. */
>>> - spin_lock_irqsave(&sched->lock, flags);
>>> - list_del(&job->link);
>>> - spin_unlock_irqrestore(&sched->lock, flags);
>>> dma_fence_put(&job->hw_fence);
>>> -
>>> drm_sched_job_cleanup(sched_job);
>>>
>>> /* Mock job itself is freed by the kunit framework. */
>>> }
>>>
>>> +static void mock_sched_cancel_pending_fences(struct
>>> drm_gpu_scheduler *gsched)
>>
>> "gsched" feels like a first time invention. Maybe drm_sched?
>
> Alright
>
>>
>>> +{
>>> + struct drm_mock_sched_job *job, *next;
>>> + struct drm_mock_scheduler *sched;
>>> + unsigned long flags;
>>> +
>>> + sched = container_of(gsched, struct drm_mock_scheduler,
>>> base);
>>> +
>>> + spin_lock_irqsave(&sched->lock, flags);
>>> + list_for_each_entry_safe(job, next, &sched->job_list,
>>> link)
>>> + drm_mock_sched_job_complete(job, -ECANCELED);
>>> + spin_unlock_irqrestore(&sched->lock, flags);
>>
>> Canceling of the timers belongs in this call back I think. Otherwise
>> jobs are not fully cancelled.
>
> I wouldn't say so – the timers represent things like the hardware
> interrupts. And those must be deactivated by the driver itself.
>
> See, one big reason why I like my approach is that the contract between
> driver and scheduler is made very simple:
>
> "Driver, signal all fences that you ever returned through run_job() to
> this scheduler!"
>
> That always works, and the driver always has all those fences. It's
> based on the most fundamental agreement regarding dma_fences: they must
> all be signaled.
>
>>
>> Hm, I also think, conceptually, the order of first canceling the
>> timer
>> and then signaling the fence should be kept.
>
> That's the case here, no?
Sorry I got confused, I was context switching over many different topics
this week.
Okay yes, the flow with your patch is correct on the high level and is
like this:
list_for_each_entry(job, &sched->job_list, link)
hrtimer_cancel(&job->timer);
drm_sched_fini(&sched->base);
drm_sched_wqueue_stop()
-> mock_sched_cancel_pending_fences()
-> drm_mock_sched_job_complete()..
But one problem is that you have no locking around the list walk and
scheduler submit wq has not been stopped yet. So AFAICT there is risk of
list corruption since mock_sched_run_job() can be called in parallel to
unit test exiting. It can also arm a new timer which will then not be
canceled and will be UAF when it fires.
> It must indeed be kept, otherwise the timers could fire after
> everything is torn down -> UAF
>
>>
>> At the moment it does not matter hugely, since the timer does not
>> signal
>> the jobs directly and will not find unlinked jobs, but if that
>> changes
>> in the future, the reversed order could cause double signaling. So if
>> you keep it in the correct logical order that potential gotcha is
>> avoided. Basically just keep the two pass approach verbatim, as is in
>> the current drm_mock_sched_fini.
>>
>> The rest of the conversion is I think good.
>
> :)
>
>>
>> Only a slight uncertainty after I cross-referenced with my version
>> (->cancel_job()) around why I needed to add signaling to
>> mock_sched_timedout_job() and manual job cleanup to the timeout test.
>> It
>> was more than a month ago that I wrote it so can't remember right
>> now.
>> You checked for memory leaks and the usual stuff?
>
> Hm, it seems I indeed ran into that leak that you fixed (in addition to
> the other stuff) in your RFC, for the timeout tests.
>
> We should fix that in a separate patch, probably.
Hm I am pretty sure that was only needed after I added ->cancel_job() so
I am not sure there is something to fix as standalone. I would have to
dive back in but that will have to wait a week or so.
Regards,
Tvrtko
>>> +}
>>> +
>>> static const struct drm_sched_backend_ops drm_mock_scheduler_ops
>>> = {
>>> .run_job = mock_sched_run_job,
>>> .timedout_job = mock_sched_timedout_job,
>>> - .free_job = mock_sched_free_job
>>> + .free_job = mock_sched_free_job,
>>> + .cancel_pending_fences = mock_sched_cancel_pending_fences,
>>> };
>>>
>>> /**
>>> @@ -265,7 +274,6 @@ struct drm_mock_scheduler
>>> *drm_mock_sched_new(struct kunit *test, long timeout)
>>> sched->hw_timeline.context = dma_fence_context_alloc(1);
>>> atomic_set(&sched->hw_timeline.next_seqno, 0);
>>> INIT_LIST_HEAD(&sched->job_list);
>>> - INIT_LIST_HEAD(&sched->done_list);
>>> spin_lock_init(&sched->lock);
>>>
>>> return sched;
>>> @@ -280,38 +288,11 @@ struct drm_mock_scheduler
>>> *drm_mock_sched_new(struct kunit *test, long timeout)
>>> */
>>> void drm_mock_sched_fini(struct drm_mock_scheduler *sched)
>>> {
>>> - struct drm_mock_sched_job *job, *next;
>>> - unsigned long flags;
>>> - LIST_HEAD(list);
>>> + struct drm_mock_sched_job *job;
>>>
>>> - drm_sched_wqueue_stop(&sched->base);
>>> -
>>> - /* Force complete all unfinished jobs. */
>>> - spin_lock_irqsave(&sched->lock, flags);
>>> - list_for_each_entry_safe(job, next, &sched->job_list,
>>> link)
>>> - list_move_tail(&job->link, &list);
>>> - spin_unlock_irqrestore(&sched->lock, flags);
>>> -
>>> - list_for_each_entry(job, &list, link)
>>> + list_for_each_entry(job, &sched->job_list, link)
>>> hrtimer_cancel(&job->timer);
>>>
>>> - spin_lock_irqsave(&sched->lock, flags);
>>> - list_for_each_entry_safe(job, next, &list, link)
>>> - drm_mock_sched_job_complete(job);
>>> - spin_unlock_irqrestore(&sched->lock, flags);
>>> -
>>> - /*
>>> - * Free completed jobs and jobs not yet processed by the
>>> DRM scheduler
>>> - * free worker.
>>> - */
>>> - spin_lock_irqsave(&sched->lock, flags);
>>> - list_for_each_entry_safe(job, next, &sched->done_list,
>>> link)
>>> - list_move_tail(&job->link, &list);
>>> - spin_unlock_irqrestore(&sched->lock, flags);
>>> -
>>> - list_for_each_entry_safe(job, next, &list, link)
>>> - mock_sched_free_job(&job->base);
>>> -
>>> drm_sched_fini(&sched->base);
>>> }
>>>
>>> @@ -346,7 +327,7 @@ unsigned int drm_mock_sched_advance(struct
>>> drm_mock_scheduler *sched,
>>> if (sched->hw_timeline.cur_seqno < job-
>>>> hw_fence.seqno)
>>> break;
>>>
>>> - drm_mock_sched_job_complete(job);
>>> + drm_mock_sched_job_complete(job, 0);
>>> found++;
>>> }
>>> unlock:
>>> diff --git a/drivers/gpu/drm/scheduler/tests/sched_tests.h
>>> b/drivers/gpu/drm/scheduler/tests/sched_tests.h
>>> index 27caf8285fb7..22e530d87791 100644
>>> --- a/drivers/gpu/drm/scheduler/tests/sched_tests.h
>>> +++ b/drivers/gpu/drm/scheduler/tests/sched_tests.h
>>> @@ -32,9 +32,8 @@
>>> *
>>> * @base: DRM scheduler base class
>>> * @test: Backpointer to owning the kunit test case
>>> - * @lock: Lock to protect the simulated @hw_timeline, @job_list
>>> and @done_list
>>> + * @lock: Lock to protect the simulated @hw_timeline and @job_list
>>> * @job_list: List of jobs submitted to the mock GPU
>>> - * @done_list: List of jobs completed by the mock GPU
>>> * @hw_timeline: Simulated hardware timeline has a @context,
>>> @next_seqno and
>>> * @cur_seqno for implementing a struct dma_fence
>>> signaling the
>>> * simulated job completion.
>>> @@ -49,7 +48,6 @@ struct drm_mock_scheduler {
>>>
>>> spinlock_t lock;
>>> struct list_head job_list;
>>> - struct list_head done_list;
>>>
>>> struct {
>>> u64 context;
>>
>
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