[PATCH v9 2/2] drm/sched: Add pending job list iterator

[Matthew Brost <matthew.brost@intel.com>]

Stop open coding pending job list in drivers. Add pending job list
iterator which safely walks DRM scheduler list asserting DRM scheduler
is stopped.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>

---

v2:
 - Fix checkpatch (CI)
v3:
 - Drop locked version (Christian)
v4:
 - Reorder patch (Niranjana)
v9:
 - Update drm_sched_for_each_pending_job() kernel doc (Philipp)
---
 drivers/gpu/drm/scheduler/sched_main.c |  4 ++-
 include/drm/gpu_scheduler.h            | 50 ++++++++++++++++++++++++++
 2 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 5f08719a35f5..bd7936c03da2 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -729,7 +729,9 @@ EXPORT_SYMBOL(drm_sched_start);
  *
  * Drivers can still save and restore their state for recovery operations, but
  * we shouldn't make this a general scheduler feature around the dma_fence
- * interface.
+ * interface. The suggested driver-side replacement is to use
+ * drm_sched_for_each_pending_job() after stopping the scheduler and implement
+ * their own recovery operations.
  */
 void drm_sched_resubmit_jobs(struct drm_gpu_scheduler *sched)
 {
diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index 86b6075ce799..78e07c2507c7 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -700,4 +700,54 @@ void drm_sched_entity_modify_sched(struct drm_sched_entity *entity,
 				   struct drm_gpu_scheduler **sched_list,
 				   unsigned int num_sched_list);
 
+/**
+ * struct drm_sched_pending_job_iter - DRM scheduler pending job iterator state
+ * @sched: DRM scheduler associated with pending job iterator
+ */
+struct drm_sched_pending_job_iter {
+	struct drm_gpu_scheduler *sched;
+};
+
+/* Drivers should never call this directly */
+static inline struct drm_sched_pending_job_iter
+__drm_sched_pending_job_iter_begin(struct drm_gpu_scheduler *sched)
+{
+	struct drm_sched_pending_job_iter iter = {
+		.sched = sched,
+	};
+
+	WARN_ON(!drm_sched_is_stopped(sched));
+	return iter;
+}
+
+/* Drivers should never call this directly */
+static inline void
+__drm_sched_pending_job_iter_end(const struct drm_sched_pending_job_iter iter)
+{
+	WARN_ON(!drm_sched_is_stopped(iter.sched));
+}
+
+DEFINE_CLASS(drm_sched_pending_job_iter, struct drm_sched_pending_job_iter,
+	     __drm_sched_pending_job_iter_end(_T),
+	     __drm_sched_pending_job_iter_begin(__sched),
+	     struct drm_gpu_scheduler *__sched);
+static inline void *
+class_drm_sched_pending_job_iter_lock_ptr(class_drm_sched_pending_job_iter_t *_T)
+{ return _T; }
+#define class_drm_sched_pending_job_iter_is_conditional false
+
+/**
+ * drm_sched_for_each_pending_job() - Iterator for each pending job in scheduler
+ * @__job: Current pending job being iterated over
+ * @__sched: DRM scheduler to iterate over pending jobs
+ * @__entity: DRM scheduler entity to filter jobs, NULL indicates no filter
+ *
+ * Iterator for each pending job in scheduler, filtering on an entity, and
+ * enforcing scheduler is fully stopped
+ */
+#define drm_sched_for_each_pending_job(__job, __sched, __entity)		\
+	scoped_guard(drm_sched_pending_job_iter, (__sched))			\
+		list_for_each_entry((__job), &(__sched)->pending_list, list)	\
+			for_each_if(!(__entity) || (__job)->entity == (__entity))
+
 #endif
-- 
2.34.1