[RFC] Revert "drm/sched: Split free_job into own work item"

From: Mario Limonciello
Date: Tue Jan 23 2024 - 01:21:22 EST


commit f7fe64ad0f22 ("drm/sched: Split free_job into own work item")
causes graphics hangs at GDM or right after logging in on a
Framework 13 AMD laptop (containing a Phoenix APU).

This reverts commit f7fe64ad0f22ff034f8ebcfbd7299ee9cc9b57d7.

Fixes: f7fe64ad0f22 ("drm/sched: Split free_job into own work item")
Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
This is a regression introduced in 6.8-rc1, bisected from 6.7.
This revert done on top of 6.8-rc1 fixes the issue.

I'm happy to gather any data to use to properly debug if that is
preferable to a revert.
---
drivers/gpu/drm/scheduler/sched_main.c | 133 +++++++++----------------
include/drm/gpu_scheduler.h | 4 +-
2 files changed, 48 insertions(+), 89 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 550492a7a031..91c96ab53fb5 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -369,32 +369,6 @@ static void drm_sched_run_job_queue(struct drm_gpu_scheduler *sched)
queue_work(sched->submit_wq, &sched->work_run_job);
}

-/**
- * __drm_sched_run_free_queue - enqueue free-job work
- * @sched: scheduler instance
- */
-static void __drm_sched_run_free_queue(struct drm_gpu_scheduler *sched)
-{
- if (!READ_ONCE(sched->pause_submit))
- queue_work(sched->submit_wq, &sched->work_free_job);
-}
-
-/**
- * drm_sched_run_free_queue - enqueue free-job work if ready
- * @sched: scheduler instance
- */
-static void drm_sched_run_free_queue(struct drm_gpu_scheduler *sched)
-{
- struct drm_sched_job *job;
-
- spin_lock(&sched->job_list_lock);
- job = list_first_entry_or_null(&sched->pending_list,
- struct drm_sched_job, list);
- if (job && dma_fence_is_signaled(&job->s_fence->finished))
- __drm_sched_run_free_queue(sched);
- spin_unlock(&sched->job_list_lock);
-}
-
/**
* drm_sched_job_done - complete a job
* @s_job: pointer to the job which is done
@@ -414,7 +388,7 @@ static void drm_sched_job_done(struct drm_sched_job *s_job, int result)
dma_fence_get(&s_fence->finished);
drm_sched_fence_finished(s_fence, result);
dma_fence_put(&s_fence->finished);
- __drm_sched_run_free_queue(sched);
+ drm_sched_run_job_queue(sched);
}

/**
@@ -1092,10 +1066,8 @@ drm_sched_get_finished_job(struct drm_gpu_scheduler *sched)
typeof(*next), list);

if (next) {
- if (test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT,
- &next->s_fence->scheduled.flags))
- next->s_fence->scheduled.timestamp =
- dma_fence_timestamp(&job->s_fence->finished);
+ next->s_fence->scheduled.timestamp =
+ dma_fence_timestamp(&job->s_fence->finished);
/* start TO timer for next job */
drm_sched_start_timeout(sched);
}
@@ -1145,29 +1117,7 @@ drm_sched_pick_best(struct drm_gpu_scheduler **sched_list,
EXPORT_SYMBOL(drm_sched_pick_best);

/**
- * drm_sched_free_job_work - worker to call free_job
- *
- * @w: free job work
- */
-static void drm_sched_free_job_work(struct work_struct *w)
-{
- struct drm_gpu_scheduler *sched =
- container_of(w, struct drm_gpu_scheduler, work_free_job);
- struct drm_sched_job *job;
-
- if (READ_ONCE(sched->pause_submit))
- return;
-
- job = drm_sched_get_finished_job(sched);
- if (job)
- sched->ops->free_job(job);
-
- drm_sched_run_free_queue(sched);
- drm_sched_run_job_queue(sched);
-}
-
-/**
- * drm_sched_run_job_work - worker to call run_job
+ * drm_sched_run_job_work - main scheduler thread
*
* @w: run job work
*/
@@ -1176,50 +1126,64 @@ static void drm_sched_run_job_work(struct work_struct *w)
struct drm_gpu_scheduler *sched =
container_of(w, struct drm_gpu_scheduler, work_run_job);
struct drm_sched_entity *entity;
- struct dma_fence *fence;
- struct drm_sched_fence *s_fence;
- struct drm_sched_job *sched_job;
+ struct drm_sched_job *cleanup_job;
int r;

if (READ_ONCE(sched->pause_submit))
return;

+ cleanup_job = drm_sched_get_finished_job(sched);
entity = drm_sched_select_entity(sched);
- if (!entity)
- return;

- sched_job = drm_sched_entity_pop_job(entity);
- if (!sched_job) {
- complete_all(&entity->entity_idle);
+ if (!entity && !cleanup_job)
return; /* No more work */
- }

- s_fence = sched_job->s_fence;
+ if (cleanup_job)
+ sched->ops->free_job(cleanup_job);

- atomic_add(sched_job->credits, &sched->credit_count);
- drm_sched_job_begin(sched_job);
+ if (entity) {
+ struct dma_fence *fence;
+ struct drm_sched_fence *s_fence;
+ struct drm_sched_job *sched_job;
+
+ sched_job = drm_sched_entity_pop_job(entity);
+ if (!sched_job) {
+ complete_all(&entity->entity_idle);
+ if (!cleanup_job)
+ return; /* No more work */
+ goto again;
+ }

- trace_drm_run_job(sched_job, entity);
- fence = sched->ops->run_job(sched_job);
- complete_all(&entity->entity_idle);
- drm_sched_fence_scheduled(s_fence, fence);
+ s_fence = sched_job->s_fence;

- if (!IS_ERR_OR_NULL(fence)) {
- /* Drop for original kref_init of the fence */
- dma_fence_put(fence);
+ atomic_inc(&sched->credit_count);
+ drm_sched_job_begin(sched_job);

- r = dma_fence_add_callback(fence, &sched_job->cb,
- drm_sched_job_done_cb);
- if (r == -ENOENT)
- drm_sched_job_done(sched_job, fence->error);
- else if (r)
- DRM_DEV_ERROR(sched->dev, "fence add callback failed (%d)\n", r);
- } else {
- drm_sched_job_done(sched_job, IS_ERR(fence) ?
- PTR_ERR(fence) : 0);
+ trace_drm_run_job(sched_job, entity);
+ fence = sched->ops->run_job(sched_job);
+ complete_all(&entity->entity_idle);
+ drm_sched_fence_scheduled(s_fence, fence);
+
+ if (!IS_ERR_OR_NULL(fence)) {
+ /* Drop for original kref_init of the fence */
+ dma_fence_put(fence);
+
+ r = dma_fence_add_callback(fence, &sched_job->cb,
+ drm_sched_job_done_cb);
+ if (r == -ENOENT)
+ drm_sched_job_done(sched_job, fence->error);
+ else if (r)
+ DRM_DEV_ERROR(sched->dev, "fence add callback failed (%d)\n",
+ r);
+ } else {
+ drm_sched_job_done(sched_job, IS_ERR(fence) ?
+ PTR_ERR(fence) : 0);
+ }
+
+ wake_up(&sched->job_scheduled);
}

- wake_up(&sched->job_scheduled);
+again:
drm_sched_run_job_queue(sched);
}

@@ -1304,7 +1268,6 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
atomic_set(&sched->credit_count, 0);
INIT_DELAYED_WORK(&sched->work_tdr, drm_sched_job_timedout);
INIT_WORK(&sched->work_run_job, drm_sched_run_job_work);
- INIT_WORK(&sched->work_free_job, drm_sched_free_job_work);
atomic_set(&sched->_score, 0);
atomic64_set(&sched->job_id_count, 0);
sched->pause_submit = false;
@@ -1432,7 +1395,6 @@ void drm_sched_wqueue_stop(struct drm_gpu_scheduler *sched)
{
WRITE_ONCE(sched->pause_submit, true);
cancel_work_sync(&sched->work_run_job);
- cancel_work_sync(&sched->work_free_job);
}
EXPORT_SYMBOL(drm_sched_wqueue_stop);

@@ -1445,6 +1407,5 @@ void drm_sched_wqueue_start(struct drm_gpu_scheduler *sched)
{
WRITE_ONCE(sched->pause_submit, false);
queue_work(sched->submit_wq, &sched->work_run_job);
- queue_work(sched->submit_wq, &sched->work_free_job);
}
EXPORT_SYMBOL(drm_sched_wqueue_start);
diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index 5acc64954a88..72f64bd0a6eb 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -495,10 +495,9 @@ struct drm_sched_backend_ops {
* waits on this wait queue until all the scheduled jobs are
* finished.
* @job_id_count: used to assign unique id to the each job.
- * @submit_wq: workqueue used to queue @work_run_job and @work_free_job
+ * @submit_wq: workqueue used to queue @work_run_job
* @timeout_wq: workqueue used to queue @work_tdr
* @work_run_job: work which calls run_job op of each scheduler.
- * @work_free_job: work which calls free_job op of each scheduler.
* @work_tdr: schedules a delayed call to @drm_sched_job_timedout after the
* timeout interval is over.
* @pending_list: the list of jobs which are currently in the job queue.
@@ -528,7 +527,6 @@ struct drm_gpu_scheduler {
struct workqueue_struct *submit_wq;
struct workqueue_struct *timeout_wq;
struct work_struct work_run_job;
- struct work_struct work_free_job;
struct delayed_work work_tdr;
struct list_head pending_list;
spinlock_t job_list_lock;
--
2.34.1