Am 13.03.25 um 10:30 schrieb Philipp Stanner:
> 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.koe...@amd.com>
> Signed-off-by: Philipp Stanner <pha...@kernel.org>
Reviewed-by: Christian König <christian.koe...@amd.com>
I'm currently looking into how to fix the amdgpu CS path for gang submission
regarding this.
Any objections that I add a preload function to allocate the memory for the XA
outside of the critical section?
Regards,
Christian.
> ---
> 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);
> }
>
