Re: [PATCH 2/6] drm/sched/tests: Port to cancel_job()

[Philipp Stanner]

On Wed, 2025-07-02 at 12:25 +0100, Tvrtko Ursulin wrote:
> 
> On 02/07/2025 11:56, Philipp Stanner wrote:
> > On Wed, 2025-07-02 at 11:36 +0100, Tvrtko Ursulin wrote:
> > > 
> > > On 01/07/2025 14:21, Philipp Stanner wrote:
> > > > The GPU Scheduler now supports a new callback, cancel_job(),
> > > > which
> > > > lets
> > > > the scheduler cancel all jobs which might not yet be freed when
> > > > drm_sched_fini() runs. Using this callback allows for
> > > > significantly
> > > > simplifying the mock scheduler teardown code.
> > > > 
> > > > Implement the cancel_job() callback and adjust the code where
> > > > necessary.
> > > 
> > > Cross referencing against my version I think you missed this
> > > hunk:
> > > 
> > > --- a/drivers/gpu/drm/scheduler/tests/sched_tests.h
> > > +++ b/drivers/gpu/drm/scheduler/tests/sched_tests.h
> > > @@ -49,7 +49,6 @@ struct drm_mock_scheduler {
> > > 
> > >    	spinlock_t		lock;
> > >    	struct list_head	job_list;
> > > -	struct list_head	done_list;
> > > 
> > >    	struct {
> > >    		u64		context;
> > > 
> > 
> > Right, overlooked that one.
> > 
> > > 
> > > I also had this:
> > > 
> > > @@ -97,7 +96,8 @@ struct drm_mock_sched_job {
> > >    	struct completion	done;
> > > 
> > >    #define DRM_MOCK_SCHED_JOB_DONE		0x1
> > > -#define DRM_MOCK_SCHED_JOB_TIMEDOUT	0x2
> > > +#define DRM_MOCK_SCHED_JOB_CANCELED	0x2
> > > +#define DRM_MOCK_SCHED_JOB_TIMEDOUT	0x4
> > > 
> > > And was setting it in the callback. And since we should add a
> > > test to
> > > explicitly cover the new callback, and just the callback, that
> > > could
> > > make it very easy to do it.
> > 
> > What do you imagine that to look like? The scheduler only invokes
> > the
> > callback on tear down.
> > 
> > We also don't have tests that only test free_job() and the like, do
> > we?
> > 
> > You cannot test a callback for the scheduler, because the callback
> > is
> > implemented in the driver.
> > 
> > Callbacks are tested by using the scheduler. In this case, it's
> > tested
> > the intended way by the unit tests invoking drm_sched_free().
> 
> Something like (untested):
> 
> static void drm_sched_test_cleanup(struct kunit *test)
> {
> 	struct drm_mock_sched_entity *entity;
> 	struct drm_mock_scheduler *sched;
> 	struct drm_mock_sched_job job;
> 	bool done;
> 
> 	/*
> 	 * Check that the job cancel callback gets invoked by the
> scheduler.
> 	 */
> 
> 	sched = drm_mock_sched_new(test, MAX_SCHEDULE_TIMEOUT);
> 	entity = drm_mock_sched_entity_new(test,
> 					  
> DRM_SCHED_PRIORITY_NORMAL,
> 					   sched);
> 
> 	job = drm_mock_sched_job_new(test, entity);
> 	drm_mock_sched_job_submit(job);
> 	done = drm_mock_sched_job_wait_scheduled(job, HZ);
> 	KUNIT_ASSERT_TRUE(test, done);
> 
> 	drm_mock_sched_entity_free(entity);
> 	drm_mock_sched_fini(sched);
> 
> 	KUNIT_ASSERT_TRUE(test, job->flags &
> DRM_MOCK_SCHED_JOB_CANCELED);
> }

That could work – but it's racy.

I wonder if we want to introduce a mechanism into the mock scheduler
through which we can enforce a simulated GPU hang. Then it would never
race, and that might be useful for more advanced tests for reset
recovery and those things.

Opinions?


P.


> 
> Or via the hw fence status.
> 
> Regards,
> 
> Tvrtko
> 
> > > > Signed-off-by: Philipp Stanner <phasta@xxxxxxxxxx>
> > > > ---
> > > >    .../gpu/drm/scheduler/tests/mock_scheduler.c  | 66 +++++++--
> > > > -----
> > > > -----
> > > >    1 file changed, 23 insertions(+), 43 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/scheduler/tests/mock_scheduler.c
> > > > b/drivers/gpu/drm/scheduler/tests/mock_scheduler.c
> > > > index 49d067fecd67..2d3169d95200 100644
> > > > --- a/drivers/gpu/drm/scheduler/tests/mock_scheduler.c
> > > > +++ b/drivers/gpu/drm/scheduler/tests/mock_scheduler.c
> > > > @@ -63,7 +63,7 @@ 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);
> > > >    	dma_fence_signal_locked(&job->hw_fence);
> > > >    	complete(&job->done);
> > > >    }
> > > > @@ -236,26 +236,39 @@ 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_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;
> > > > +
> > > > +	hrtimer_cancel(&job->timer);
> > > > +
> > > > +	spin_lock_irqsave(&sched->lock, flags);
> > > > +	if (!dma_fence_is_signaled_locked(&job->hw_fence)) {
> > > > +		list_del(&job->link);
> > > > +		dma_fence_set_error(&job->hw_fence, -
> > > > ECANCELED);
> > > > +		dma_fence_signal_locked(&job->hw_fence);
> > > > +	}
> > > > +	spin_unlock_irqrestore(&sched->lock, flags);
> > > > +
> > > > +	/* The GPU Scheduler will call
> > > > drm_sched_backend_ops.free_job(), still.
> > > > +	 * Mock job itself is freed by the kunit framework. */
> > > 
> > > /*
> > >    * Multiline comment style to stay consistent, at least in this
> > > file.
> > >    */
> > > 
> > > The rest looks good, but I need to revisit the timeout/free
> > > handling
> > > since it has been a while and you changed it recently.
> > > 
> > > 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_job = mock_sched_cancel_job,
> > > >    };
> > > >    
> > > >    /**
> > > > @@ -289,7 +302,6 @@ 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;
> > > > @@ -304,38 +316,6 @@ 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);
> > > > -
> > > > -	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)
> > > > -		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);
> > > >    }
> > > >    
> > > 
> > 
>