The documentation for drm_sched_job_arm() and especially
drm_sched_job_cleanup() does not make it very clear why
drm_sched_job_arm() is a point of no return, which it indeed is.
Make the nature of drm_sched_job_arm() in the docu as clear as possible.
Suggested-by: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Philipp Stanner <phasta@xxxxxxxxxx>
---
drivers/gpu/drm/scheduler/sched_main.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 4d4219fbe49d..829579c41c6b 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -828,11 +828,15 @@ EXPORT_SYMBOL(drm_sched_job_init);
*
* This arms a scheduler job for execution. Specifically it initializes the
* &drm_sched_job.s_fence of @job, so that it can be attached to struct dma_resv
- * or other places that need to track the completion of this job.
+ * or other places that need to track the completion of this job. It also
+ * initializes sequence numbers, which are fundamental for fence ordering.
*
* Refer to drm_sched_entity_push_job() documentation for locking
* considerations.
*
+ * Once this function was called, you *must* submit @job with
+ * drm_sched_entity_push_job().
+ *
* This can only be called if drm_sched_job_init() succeeded.
*/
void drm_sched_job_arm(struct drm_sched_job *job)
@@ -1017,9 +1021,12 @@ EXPORT_SYMBOL(drm_sched_job_has_dependency);
* Drivers should call this from their error unwind code if @job is aborted
* before drm_sched_job_arm() is called.
*
- * After that point of no return @job is committed to be executed by the
- * scheduler, and this function should be called from the
- * &drm_sched_backend_ops.free_job callback.
+ * drm_sched_job_arm() is a point of no return since it initializes the fences
+ * and their sequence number etc. Once that function has been called, you *must*
+ * submit it with drm_sched_entity_push_job() and cannot simply abort it by
+ * calling drm_sched_job_cleanup().
+ *
+ * This function should be called in the &drm_sched_backend_ops.free_job callback.
*/
void drm_sched_job_cleanup(struct drm_sched_job *job)
{
@@ -1027,10 +1034,15 @@ void drm_sched_job_cleanup(struct drm_sched_job *job)
unsigned long index;
if (kref_read(&job->s_fence->finished.refcount)) {
- /* drm_sched_job_arm() has been called */
+ /* The job has been processed by the scheduler, i.e.,
+ * drm_sched_job_arm() and drm_sched_entity_push_job() have
+ * been called.
+ */
dma_fence_put(&job->s_fence->finished);
} else {
- /* aborted job before committing to run it */
+ /* The job was aborted before it has been committed to be run;
+ * notably, drm_sched_job_arm() has not been called.
+ */
drm_sched_fence_free(job->s_fence);
}
--
2.48.1
