[PATCH 1/6] drm/sched: Add internal job peek/pop API

[Philipp Stanner]

On Fri, 2025-02-07 at 14:50 +0000, Tvrtko Ursulin wrote:
> Idea is to add helpers for peeking and popping jobs from entities
> with
> the goal of decoupling the hidden assumption in the code that
> queue_node
> is the first element in struct drm_sched_job.
> 
> That assumption usually comes in the form of:
> 
>   while ((job = to_drm_sched_job(spsc_queue_pop(&entity-
> >job_queue))))
> 
> Which breaks if the queue_node is re-positioned due to_drm_sched_job
> being implemented with a container_of.
> 
> This also allows us to remove duplicate definitions of
> to_drm_sched_job.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
> Cc: Christian König <christian.koenig at amd.com>
> Cc: Danilo Krummrich <dakr at kernel.org>
> Cc: Matthew Brost <matthew.brost at intel.com>
> Cc: Philipp Stanner <phasta at kernel.org>
> ---
>  drivers/gpu/drm/scheduler/sched_entity.c   | 11 +++---
>  drivers/gpu/drm/scheduler/sched_internal.h | 46
> ++++++++++++++++++++++
>  drivers/gpu/drm/scheduler/sched_main.c     |  7 ++--
>  3 files changed, 54 insertions(+), 10 deletions(-)
>  create mode 100644 drivers/gpu/drm/scheduler/sched_internal.h
> 
> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c
> b/drivers/gpu/drm/scheduler/sched_entity.c
> index 69bcf0e99d57..a171f05ad761 100644
> --- a/drivers/gpu/drm/scheduler/sched_entity.c
> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> @@ -28,11 +28,10 @@
>  #include <drm/drm_print.h>
>  #include <drm/gpu_scheduler.h>
>  
> +#include "sched_internal.h"
> +
>  #include "gpu_scheduler_trace.h"
>  
> -#define to_drm_sched_job(sched_job)		\
> -		container_of((sched_job), struct drm_sched_job,
> queue_node)
> -
>  /**
>   * drm_sched_entity_init - Init a context entity used by scheduler
> when
>   * submit to HW ring.
> @@ -255,7 +254,7 @@ static void drm_sched_entity_kill(struct
> drm_sched_entity *entity)
>  	/* The entity is guaranteed to not be used by the scheduler
> */
>  	prev = rcu_dereference_check(entity->last_scheduled, true);
>  	dma_fence_get(prev);
> -	while ((job = to_drm_sched_job(spsc_queue_pop(&entity-
> >job_queue)))) {
> +	while ((job = drm_sched_entity_queue_pop(entity))) {
>  		struct drm_sched_fence *s_fence = job->s_fence;
>  
>  		dma_fence_get(&s_fence->finished);
> @@ -477,7 +476,7 @@ struct drm_sched_job
> *drm_sched_entity_pop_job(struct drm_sched_entity *entity)
>  {
>  	struct drm_sched_job *sched_job;
>  
> -	sched_job = to_drm_sched_job(spsc_queue_peek(&entity-
> >job_queue));
> +	sched_job = drm_sched_entity_queue_peek(entity);
>  	if (!sched_job)
>  		return NULL;
>  
> @@ -513,7 +512,7 @@ struct drm_sched_job
> *drm_sched_entity_pop_job(struct drm_sched_entity *entity)
>  	if (drm_sched_policy == DRM_SCHED_POLICY_FIFO) {
>  		struct drm_sched_job *next;
>  
> -		next = to_drm_sched_job(spsc_queue_peek(&entity-
> >job_queue));
> +		next = drm_sched_entity_queue_peek(entity);
>  		if (next) {
>  			struct drm_sched_rq *rq;
>  
> diff --git a/drivers/gpu/drm/scheduler/sched_internal.h
> b/drivers/gpu/drm/scheduler/sched_internal.h
> new file mode 100644
> index 000000000000..25ac62ac2bf3
> --- /dev/null
> +++ b/drivers/gpu/drm/scheduler/sched_internal.h
> @@ -0,0 +1,46 @@
> +#ifndef _DRM_GPU_SCHEDULER_INTERNAL_H_
> +#define _DRM_GPU_SCHEDULER_INTERNAL_H_
> +
> +/**
> + * drm_sched_entity_queue_pop - Low level helper for popping queued
> jobs
> + *
> + * @entity: scheduler entity
> + *
> + * Low level helper for popping queued jobs.
> + *
> + * Returns the job dequeued or NULL.
> + */
> +static inline struct drm_sched_job *
> +drm_sched_entity_queue_pop(struct drm_sched_entity *entity)
> +{
> +	struct spsc_node *node;
> +
> +	node = spsc_queue_pop(&entity->job_queue);
> +	if (!node)
> +		return NULL;
> +
> +	return container_of(node, struct drm_sched_job, queue_node);
> +}
> +
> +/**
> + * drm_sched_entity_queue_peek - Low level helper for peeking at the
> job queue
> + *
> + * @entity: scheduler entity
> + *
> + * Low level helper for peeking at the job queue
> + *
> + * Returns the job at the head of the queue or NULL.

I would like to (slowly) work towards a unified style regarding the
docstrings. They're currently relatively inconsistent in drm/sched.

I think we should do it that way:

""
@entity: scheduler entity

Returns: the job at the head of the queue or NULL.

Low level helper for peeking at the the job queue.
""

P.

> + */
> +static inline struct drm_sched_job *
> +drm_sched_entity_queue_peek(struct drm_sched_entity *entity)
> +{
> +	struct spsc_node *node;
> +
> +	node = spsc_queue_peek(&entity->job_queue);
> +	if (!node)
> +		return NULL;
> +
> +	return container_of(node, struct drm_sched_job, queue_node);
> +}
> +
> +#endif
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c
> b/drivers/gpu/drm/scheduler/sched_main.c
> index a48be16ab84f..9f614a775c49 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -78,6 +78,8 @@
>  #include <drm/gpu_scheduler.h>
>  #include <drm/spsc_queue.h>
>  
> +#include "sched_internal.h"
> +
>  #define CREATE_TRACE_POINTS
>  #include "gpu_scheduler_trace.h"
>  
> @@ -87,9 +89,6 @@ static struct lockdep_map drm_sched_lockdep_map = {
>  };
>  #endif
>  
> -#define to_drm_sched_job(sched_job)		\
> -		container_of((sched_job), struct drm_sched_job,
> queue_node)
> -
>  int drm_sched_policy = DRM_SCHED_POLICY_FIFO;
>  
>  /**
> @@ -123,7 +122,7 @@ static bool drm_sched_can_queue(struct
> drm_gpu_scheduler *sched,
>  {
>  	struct drm_sched_job *s_job;
>  
> -	s_job = to_drm_sched_job(spsc_queue_peek(&entity-
> >job_queue));
> +	s_job = drm_sched_entity_queue_peek(entity);
>  	if (!s_job)
>  		return false;
>