On 2023-04-03 20:22, Matthew Brost wrote:
> Add generic schedule message interface which sends messages to backend
> from the drm_gpu_scheduler main submission thread. The idea is some of
> these messages modify some state in drm_sched_entity which is also
> modified during submission. By scheduling these messages and submission
> in the same thread their is not race changing states in
> drm_sched_entity.
"... there is no race when changing ..." or better yet,
"... we eliminate races due to drm_sched_entity state changes."
>
> This interface will be used in XE, new Intel GPU driver, to cleanup,
"Xe"?
Regards,
Luben
> suspend, resume, and change scheduling properties of a drm_sched_entity.
>
> The interface is designed to be generic and extendable with only the
> backend understanding the messages.
>
> Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> ---
> drivers/gpu/drm/scheduler/sched_main.c | 58 +++++++++++++++++++++++++-
> include/drm/gpu_scheduler.h | 29 ++++++++++++-
> 2 files changed, 84 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index 2795021efe7b..9dc3378e9c5e 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -1055,6 +1055,54 @@ drm_sched_pick_best(struct drm_gpu_scheduler **sched_list,
> }
> EXPORT_SYMBOL(drm_sched_pick_best);
>
> +/**
> + * drm_sched_add_msg - add scheduler message
> + *
> + * @sched: scheduler instance
> + * @msg: message to be added
> + *
> + * Can and will pass an jobs waiting on dependencies or in a runnable queue.
> + * Messages processing will stop if schedule run wq is stopped and resume when
> + * run wq is started.
> + */
> +void drm_sched_add_msg(struct drm_gpu_scheduler *sched,
> + struct drm_sched_msg *msg)
> +{
> + spin_lock(&sched->job_list_lock);
> + list_add_tail(&msg->link, &sched->msgs);
> + spin_unlock(&sched->job_list_lock);
> +
> + /*
> + * Same as above in drm_sched_run_wq_queue, try to kick worker if
> + * paused, harmless if this races
> + */
> + if (!sched->pause_run_wq)
> + queue_work(sched->run_wq, &sched->work_run);
> +}
> +EXPORT_SYMBOL(drm_sched_add_msg);
> +
> +/**
> + * drm_sched_get_msg - get scheduler message
> + *
> + * @sched: scheduler instance
> + *
> + * Returns NULL or message
> + */
> +static struct drm_sched_msg *
> +drm_sched_get_msg(struct drm_gpu_scheduler *sched)
> +{
> + struct drm_sched_msg *msg;
> +
> + spin_lock(&sched->job_list_lock);
> + msg = list_first_entry_or_null(&sched->msgs,
> + struct drm_sched_msg, link);
> + if (msg)
> + list_del(&msg->link);
> + spin_unlock(&sched->job_list_lock);
> +
> + return msg;
> +}
> +
> /**
> * drm_sched_main - main scheduler thread
> *
> @@ -1068,6 +1116,7 @@ static void drm_sched_main(struct work_struct *w)
>
> while (!READ_ONCE(sched->pause_run_wq)) {
> struct drm_sched_entity *entity;
> + struct drm_sched_msg *msg;
> struct drm_sched_fence *s_fence;
> struct drm_sched_job *sched_job;
> struct dma_fence *fence;
> @@ -1075,12 +1124,16 @@ static void drm_sched_main(struct work_struct *w)
>
> cleanup_job = drm_sched_get_cleanup_job(sched);
> entity = drm_sched_select_entity(sched);
> + msg = drm_sched_get_msg(sched);
>
> if (cleanup_job)
> sched->ops->free_job(cleanup_job);
>
> + if (msg)
> + sched->ops->process_msg(msg);
> +
> if (!entity) {
> - if (!cleanup_job)
> + if (!cleanup_job && !msg)
> break;
> continue;
> }
> @@ -1089,7 +1142,7 @@ static void drm_sched_main(struct work_struct *w)
>
> if (!sched_job) {
> complete_all(&entity->entity_idle);
> - if (!cleanup_job)
> + if (!cleanup_job && !msg)
> break;
> continue;
> }
> @@ -1181,6 +1234,7 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
>
> init_waitqueue_head(&sched->job_scheduled);
> INIT_LIST_HEAD(&sched->pending_list);
> + INIT_LIST_HEAD(&sched->msgs);
> spin_lock_init(&sched->job_list_lock);
> atomic_set(&sched->hw_rq_count, 0);
> INIT_DELAYED_WORK(&sched->work_tdr, drm_sched_job_timedout);
> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> index 3e421f5a710c..18172ae63ab7 100644
> --- a/include/drm/gpu_scheduler.h
> +++ b/include/drm/gpu_scheduler.h
> @@ -398,6 +398,23 @@ enum drm_gpu_sched_stat {
> DRM_GPU_SCHED_STAT_ENODEV,
> };
>
> +/**
> + * struct drm_sched_msg - an in-band (relative to GPU scheduler run queue)
> + * message
> + *
> + * Generic enough for backend defined messages, backend can expand if needed.
> + */
> +struct drm_sched_msg {
> + /** @link: list link into the gpu scheduler list of messages */
> + struct list_head link;
> + /**
> + * @private_data: opaque pointer to message private data (backend defined)
> + */
> + void *private_data;
> + /** @opcode: opcode of message (backend defined) */
> + unsigned int opcode;
> +};
> +
> /**
> * struct drm_sched_backend_ops - Define the backend operations
> * called by the scheduler
> @@ -475,6 +492,12 @@ struct drm_sched_backend_ops {
> * and it's time to clean it up.
> */
> void (*free_job)(struct drm_sched_job *sched_job);
> +
> + /**
> + * @process_msg: Process a message. Allowed to block, it is this
> + * function's responsibility to free message if dynamically allocated.
> + */
> + void (*process_msg)(struct drm_sched_msg *msg);
> };
>
> /**
> @@ -486,6 +509,7 @@ struct drm_sched_backend_ops {
> * @timeout: the time after which a job is removed from the scheduler.
> * @name: name of the ring for which this scheduler is being used.
> * @sched_rq: priority wise array of run queues.
> + * @msgs: list of messages to be processed in @work_run
> * @job_scheduled: once @drm_sched_entity_do_release is called the scheduler
> * waits on this wait queue until all the scheduled jobs are
> * finished.
> @@ -493,7 +517,7 @@ struct drm_sched_backend_ops {
> * @job_id_count: used to assign unique id to the each job.
> * @run_wq: workqueue used to queue @work_run
> * @timeout_wq: workqueue used to queue @work_tdr
> - * @work_run: schedules jobs and cleans up entities
> + * @work_run: schedules jobs, cleans up jobs, and processes messages
> * @work_tdr: schedules a delayed call to @drm_sched_job_timedout after the
> * timeout interval is over.
> * @pending_list: the list of jobs which are currently in the job queue.
> @@ -517,6 +541,7 @@ struct drm_gpu_scheduler {
> long timeout;
> const char *name;
> struct drm_sched_rq sched_rq[DRM_SCHED_PRIORITY_COUNT];
> + struct list_head msgs;
> wait_queue_head_t job_scheduled;
> atomic_t hw_rq_count;
> atomic64_t job_id_count;
> @@ -570,6 +595,8 @@ void drm_sched_entity_modify_sched(struct drm_sched_entity *entity,
>
> void drm_sched_job_cleanup(struct drm_sched_job *job);
> void drm_sched_wakeup(struct drm_gpu_scheduler *sched);
> +void drm_sched_add_msg(struct drm_gpu_scheduler *sched,
> + struct drm_sched_msg *msg);
> void drm_sched_run_wq_stop(struct drm_gpu_scheduler *sched);
> void drm_sched_run_wq_start(struct drm_gpu_scheduler *sched);
> void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad);
