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

Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx> · Wed, 12 Feb 2025 09:32:32 +0000

On 12/02/2025 09:02, Philipp Stanner wrote:
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@xxxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: Danilo Krummrich <dakr@xxxxxxxxxx>
Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
Cc: Philipp Stanner <phasta@xxxxxxxxxx>
---
  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.
""

Returns before the description would be yet another new style, no? I's 
say that if we are churning lets follow 
Documentation/doc-guide/kernel-doc.rst. Or even consider sending a patch 
which churns everything at once.

Regards,

Tvrtko

+ */
+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;
  








