drm/sched: Optimise drm_sched_entity_push_job

[ Upstream commit d42a254633c773921884a19e8a1a0f53a31150c3 ]

In FIFO mode (which is the default), both drm_sched_entity_push_job() and
drm_sched_rq_update_fifo(), where the latter calls the former, are
currently taking and releasing the same entity->rq_lock.

We can avoid that design inelegance, and also have a miniscule
efficiency improvement on the submit from idle path, by introducing a new
drm_sched_rq_update_fifo_locked() helper and pulling up the lock taking to
its callers.

v2:
 * Remove drm_sched_rq_update_fifo() altogether. (Christian)

v3:
 * Improved commit message. (Philipp)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Luben Tuikov <ltuikov89@gmail.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Philipp Stanner <pstanner@redhat.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Philipp Stanner <pstanner@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241016122013.7857-2-tursulin@igalia.com
Stable-dep-of: d25e3a610bae ("drm/sched: Fix race in drm_sched_entity_select_rq()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index a9952d86fd3613cf36d44d729f6e44c27b270b91..7ac5d7776aa3167e5cfb411a0b67e2247a32e166 100644 (file)
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -506,8 +506,12 @@ struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity *entity)
                struct drm_sched_job *next;
 
                next = to_drm_sched_job(spsc_queue_peek(&entity->job_queue));
-               if (next)
-                       drm_sched_rq_update_fifo(entity, next->submit_ts);
+               if (next) {
+                       spin_lock(&entity->rq_lock);
+                       drm_sched_rq_update_fifo_locked(entity,
+                                                       next->submit_ts);
+                       spin_unlock(&entity->rq_lock);
+               }
        }
 
        /* Jobs and entities might have different lifecycles. Since we're
@@ -607,10 +611,11 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
                sched = rq->sched;
 
                drm_sched_rq_add_entity(rq, entity);
-               spin_unlock(&entity->rq_lock);
 
                if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
-                       drm_sched_rq_update_fifo(entity, submit_ts);
+                       drm_sched_rq_update_fifo_locked(entity, submit_ts);
+
+               spin_unlock(&entity->rq_lock);
 
                drm_sched_wakeup(sched);
        }

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index d5260cb1ed0ec60e86492c06fa05611d56ada923..0b7976c908ddea7ff99edd708bf1a96f37a1b1e6 100644 (file)
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -169,14 +169,15 @@ static inline void drm_sched_rq_remove_fifo_locked(struct drm_sched_entity *enti
        }
 }
 
-void drm_sched_rq_update_fifo(struct drm_sched_entity *entity, ktime_t ts)
+void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity, ktime_t ts)
 {
        /*
         * Both locks need to be grabbed, one to protect from entity->rq change
         * for entity from within concurrent drm_sched_entity_select_rq and the
         * other to update the rb tree structure.
         */
-       spin_lock(&entity->rq_lock);
+       lockdep_assert_held(&entity->rq_lock);
+
        spin_lock(&entity->rq->lock);
 
        drm_sched_rq_remove_fifo_locked(entity);
@@ -187,7 +188,6 @@ void drm_sched_rq_update_fifo(struct drm_sched_entity *entity, ktime_t ts)
                      drm_sched_entity_compare_before);
 
        spin_unlock(&entity->rq->lock);
-       spin_unlock(&entity->rq_lock);
 }
 
 /**

diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index 9c437a057e5de15f321f8c47b8e69a90beec8b76..346a3c261b437aa821af5ff3f6980e3f3b36518d 100644 (file)
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -593,7 +593,7 @@ void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
 void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
                                struct drm_sched_entity *entity);
 
-void drm_sched_rq_update_fifo(struct drm_sched_entity *entity, ktime_t ts);
+void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity, ktime_t ts);
 
 int drm_sched_entity_init(struct drm_sched_entity *entity,
                          enum drm_sched_priority priority,