drm/sched/tests: Make timedout_job callback a better role model

Since the drm_mock_scheduler does not have real users in userspace, nor
does it have real hardware or firmware rings, it's not necessary to
signal timedout fences nor free jobs - from a functional standpoint.
Still, the dma_fence framework establishes the hard rule that all fences
must always get signaled.

The unit tests, moreover, should as much as possible represent the
intended usage of the scheduler API.

Furthermore, this later enables simplifying the mock scheduler's
teardown code path.

Make sure timed out hardware fences get signaled with the appropriate
error code.

Signed-off-by: Philipp Stanner <phasta@kernel.org>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20250605134154.191764-2-phasta@kernel.org

Author: Philipp Stanner

drivers/gpu/drm/scheduler/tests/mock_scheduler.c

@@ -200,12 +200,36 @@ static struct dma_fence *mock_sched_run_job(struct drm_sched_job *sched_job)
 	return &job->hw_fence;
 }
 
+/*
+ * Normally, drivers would take appropriate measures in this callback, such as
+ * killing the entity the faulty job is associated with, resetting the hardware
+ * and / or resubmitting non-faulty jobs.
+ *
+ * For the mock scheduler, there are no hardware rings to be resetted nor jobs
+ * to be resubmitted. Thus, this function merely ensures that
+ *   a) timedout fences get signaled properly and removed from the pending list
+ *   b) the mock scheduler framework gets informed about the timeout via a flag
+ *   c) The drm_sched_job, not longer needed, gets freed
+ */
 static enum drm_gpu_sched_stat
 mock_sched_timedout_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;
 
-	job->flags |= DRM_MOCK_SCHED_JOB_TIMEDOUT;
+	spin_lock_irqsave(&sched->lock, flags);
+	if (!dma_fence_is_signaled_locked(&job->hw_fence)) {
+		list_del(&job->link);
+		job->flags |= DRM_MOCK_SCHED_JOB_TIMEDOUT;
+		dma_fence_set_error(&job->hw_fence, -ETIMEDOUT);
+		dma_fence_signal_locked(&job->hw_fence);
+	}
+	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. */
 
 	return DRM_GPU_SCHED_STAT_NOMINAL;
 }