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drm/sched: Avoid memory leaks with cancel_job() callback 

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 safely 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/
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Acked-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://lore.kernel.org/r/20250710125412.128476-4-phasta@kernel.org
This commit is contained in:
Philipp Stanner 2025-07-10 14:54:06 +02:00
parent fe69a39180
commit bf8bbaefaa
2 changed files with 39 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
drivers/gpu/drm/scheduler/sched_main.c
View File

@ -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_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
*
@ -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_cancel_remaining_jobs(sched);
if (sched->own_submit_wq)
destroy_workqueue(sched->submit_wq);
sched->ready = false;

18
include/drm/gpu_scheduler.h
View File

@ -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);
};
/**