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.ursulin@igalia.com>
Link: https://lore.kernel.org/dri-devel/20250418113211.69956-1-tvrtko.ursulin@igalia.com/
Signed-off-by: Philipp Stanner <phasta@kernel.org>
---
drivers/gpu/drm/scheduler/sched_main.c | 34 ++++++++++++++++----------
include/drm/gpu_scheduler.h | 18 ++++++++++++++
2 files changed, 39 insertions(+), 13 deletions(-)
diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index c63543132f9d..1239954f5f7c 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -1353,6 +1353,18 @@ int drm_sched_init(struct drm_gpu_scheduler *sched, const struct drm_sched_init_
}
EXPORT_SYMBOL(drm_sched_init);
+static void drm_sched_cancel_remaining_jobs(struct drm_gpu_scheduler *sched)
+{
+ 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
*
@@ -1360,19 +1372,11 @@ 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)
{
@@ -1402,6 +1406,10 @@ 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_cancel_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..190844370f48 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -512,6 +512,24 @@ 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().
+ *
+ * Used by the scheduler to cancel all jobs that have not been executed
+ * with &struct drm_sched_backend_ops.run_job by the time
+ * drm_sched_fini() gets invoked.
+ *
+ * Drivers need to signal the passed job's hardware fence with an
+ * appropriate error code (e.g., -ECANCELED) in this callback. They
+ * must not free the job.
+ *
+ * The scheduler will only call this callback once it stopped calling
+ * all other callbacks forever, with the exception of &struct
+ * drm_sched_backend_ops.free_job.
+ */
+ void (*cancel_job)(struct drm_sched_job *sched_job);
};
/**
--
2.49.0Hi Philipp, On 01/07/25 10:21, 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() s/savely/safely > callback for freeing the job. > > Implement the new backend_ops callback cancel_job(). > > Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com> > Link: https://lore.kernel.org/dri-devel/20250418113211.69956-1-tvrtko.ursulin@igalia.com/ > Signed-off-by: Philipp Stanner <phasta@kernel.org> Reviewed-by: Maíra Canal <mcanal@igalia.com> Best Regards, - Maíra
On 01/07/2025 14:21, 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.ursulin@igalia.com>
> Link: https://lore.kernel.org/dri-devel/20250418113211.69956-1-tvrtko.ursulin@igalia.com/
> Signed-off-by: Philipp Stanner <phasta@kernel.org>
> ---
> drivers/gpu/drm/scheduler/sched_main.c | 34 ++++++++++++++++----------
> include/drm/gpu_scheduler.h | 18 ++++++++++++++
> 2 files changed, 39 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index c63543132f9d..1239954f5f7c 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -1353,6 +1353,18 @@ int drm_sched_init(struct drm_gpu_scheduler *sched, const struct drm_sched_init_
> }
> EXPORT_SYMBOL(drm_sched_init);
>
> +static void drm_sched_cancel_remaining_jobs(struct drm_gpu_scheduler *sched)
> +{
> + 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);
List_del is just for the warning in 3/6 I guess? You could in theory zap
the whole list in one go and avoid the safe iterator. Not that it
matters really so:
Acked-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Regards,
Tvrtko
> + sched->ops->free_job(job);
> + }
> +}
> +
> /**
> * drm_sched_fini - Destroy a gpu scheduler
> *
> @@ -1360,19 +1372,11 @@ 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)
> {
> @@ -1402,6 +1406,10 @@ 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_cancel_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..190844370f48 100644
> --- a/include/drm/gpu_scheduler.h
> +++ b/include/drm/gpu_scheduler.h
> @@ -512,6 +512,24 @@ 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().
> + *
> + * Used by the scheduler to cancel all jobs that have not been executed
> + * with &struct drm_sched_backend_ops.run_job by the time
> + * drm_sched_fini() gets invoked.
> + *
> + * Drivers need to signal the passed job's hardware fence with an
> + * appropriate error code (e.g., -ECANCELED) in this callback. They
> + * must not free the job.
> + *
> + * The scheduler will only call this callback once it stopped calling
> + * all other callbacks forever, with the exception of &struct
> + * drm_sched_backend_ops.free_job.
> + */
> + void (*cancel_job)(struct drm_sched_job *sched_job);
> };
>
> /**
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