On 03/06/2025 10:31, Philipp Stanner wrote:
Since its inception, the GPU scheduler can leak memory if the driver
calls drm_sched_fini() while there are still jobs in flight.
The simplest way to solve this in a backwards compatible manner is by
adding a new callback, drm_sched_backend_ops.cancel_job(), which
instructs the driver to signal the hardware fence associated with the
job. Afterwards, the scheduler can savely use the established free_job()
callback for freeing the job.
Implement the new backend_ops callback cancel_job().
Suggested-by: Tvrtko Ursulin <tvrtko.ursu...@igalia.com>
Signed-off-by: Philipp Stanner <pha...@kernel.org>
---
drivers/gpu/drm/scheduler/sched_main.c | 34 ++++++++++++++++----------
include/drm/gpu_scheduler.h | 9 +++++++
2 files changed, 30 insertions(+), 13 deletions(-)
diff --git a/drivers/gpu/drm/scheduler/sched_main.c
b/drivers/gpu/drm/scheduler/sched_main.c
index d20726d7adf0..3f14f1e151fa 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -1352,6 +1352,18 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
const struct drm_sched_init_
}
EXPORT_SYMBOL(drm_sched_init);
+static void drm_sched_kill_remaining_jobs(struct drm_gpu_scheduler *sched)
Only some bikeshedding comments, no need to act on them.
1)
I would maybe s/kill/cancel/ to align with the ->cancel_job naming.
2)
Would the callback presence check look better inside this helper so it
is all consolidated and streamlined?
Regards,
Tvrtko
+{
+ struct drm_sched_job *job, *tmp;
+
+ /* All other accessors are stopped. No locking necessary. */
+ list_for_each_entry_safe_reverse(job, tmp, &sched->pending_list, list) {
+ sched->ops->cancel_job(job);
+ list_del(&job->list);
+ sched->ops->free_job(job);
+ }
+}
+
/**
* drm_sched_fini - Destroy a gpu scheduler
*
@@ -1359,19 +1371,11 @@ EXPORT_SYMBOL(drm_sched_init);
*
* Tears down and cleans up the scheduler.
*
- * This stops submission of new jobs to the hardware through
- * drm_sched_backend_ops.run_job(). Consequently,
drm_sched_backend_ops.free_job()
- * will not be called for all jobs still in drm_gpu_scheduler.pending_list.
- * There is no solution for this currently. Thus, it is up to the driver to
make
- * sure that:
- *
- * a) drm_sched_fini() is only called after for all submitted jobs
- * drm_sched_backend_ops.free_job() has been called or that
- * b) the jobs for which drm_sched_backend_ops.free_job() has not been called
- * after drm_sched_fini() ran are freed manually.
- *
- * FIXME: Take care of the above problem and prevent this function from leaking
- * the jobs in drm_gpu_scheduler.pending_list under any circumstances.
+ * This stops submission of new jobs to the hardware through &struct
+ * drm_sched_backend_ops.run_job. If &struct drm_sched_backend_ops.cancel_job
+ * is implemented, all jobs will be canceled through it and afterwards cleaned
+ * up through &struct drm_sched_backend_ops.free_job. If cancel_job is not
+ * implemented, memory could leak.
*/
void drm_sched_fini(struct drm_gpu_scheduler *sched)
{
@@ -1401,6 +1405,10 @@ void drm_sched_fini(struct drm_gpu_scheduler *sched)
/* Confirm no work left behind accessing device structures */
cancel_delayed_work_sync(&sched->work_tdr);
+ /* Avoid memory leaks if supported by the driver. */
+ if (sched->ops->cancel_job)
+ drm_sched_kill_remaining_jobs(sched);
+
if (sched->own_submit_wq)
destroy_workqueue(sched->submit_wq);
sched->ready = false;
diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index e62a7214e052..81dcbfc8c223 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -512,6 +512,15 @@ struct drm_sched_backend_ops {
* and it's time to clean it up.
*/
void (*free_job)(struct drm_sched_job *sched_job);
+
+ /**
+ * @cancel_job: Used by the scheduler to guarantee remaining jobs'
fences
+ * get signaled in drm_sched_fini().
+ *
+ * Drivers need to signal the passed job's hardware fence with
+ * -ECANCELED in this callback. They must not free the job.
+ */
+ void (*cancel_job)(struct drm_sched_job *sched_job);
};
/**
