drm/sched: Add internal job peek/pop API

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@igalia.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Philipp Stanner <phasta@kernel.org>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250221105038.79665-2-tvrtko.ursulin@igalia.com

drivers/gpu/drm/scheduler/sched_entity.c

@@ -28,10 +28,9 @@
 #include <drm/drm_print.h>
 #include <drm/gpu_scheduler.h>
 
-#include "gpu_scheduler_trace.h"
+#include "sched_internal.h"
 
-#define to_drm_sched_job(sched_job)		\
-		container_of((sched_job), struct drm_sched_job, queue_node)
+#include "gpu_scheduler_trace.h"
 
 /**
  * drm_sched_entity_init - Init a context entity used by scheduler when
@@ -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;
 

drivers/gpu/drm/scheduler/sched_internal.h

@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: MIT */
+
+#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.
+ */
+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

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;