From baf4afc5831438b35de4b0e951b9cd58435a6d99 Mon Sep 17 00:00:00 2001 From: Philipp Stanner Date: Tue, 5 Nov 2024 15:31:38 +0100 Subject: [PATCH] drm/sched: Improve teardown documentation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit If jobs are still enqueued in struct drm_gpu_scheduler.pending_list when drm_sched_fini() gets called, those jobs will be leaked since that function stops both job-submission and (automatic) job-cleanup. It is, thus, up to the driver to take care of preventing leaks. The related function drm_sched_wqueue_stop() also prevents automatic job cleanup. Those pitfals are not reflected in the documentation, currently. Explicitly inform about the leak problem in the docstring of drm_sched_fini(). Additionally, detail the purpose of drm_sched_wqueue_{start,stop} and hint at the consequences for automatic cleanup. Signed-off-by: Philipp Stanner Reviewed-by: Christian König Link: https://patchwork.freedesktop.org/patch/msgid/20241105143137.71893-2-pstanner@redhat.com --- drivers/gpu/drm/scheduler/sched_main.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c index eeaf71d431916..7ce25281c74ce 100644 --- a/drivers/gpu/drm/scheduler/sched_main.c +++ b/drivers/gpu/drm/scheduler/sched_main.c @@ -1350,6 +1350,19 @@ EXPORT_SYMBOL(drm_sched_init); * @sched: scheduler instance * * 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. */ void drm_sched_fini(struct drm_gpu_scheduler *sched) { @@ -1445,8 +1458,10 @@ EXPORT_SYMBOL(drm_sched_wqueue_ready); /** * drm_sched_wqueue_stop - stop scheduler submission - * * @sched: scheduler instance + * + * Stops the scheduler from pulling new jobs from entities. It also stops + * freeing jobs automatically through drm_sched_backend_ops.free_job(). */ void drm_sched_wqueue_stop(struct drm_gpu_scheduler *sched) { @@ -1458,8 +1473,12 @@ EXPORT_SYMBOL(drm_sched_wqueue_stop); /** * drm_sched_wqueue_start - start scheduler submission - * * @sched: scheduler instance + * + * Restarts the scheduler after drm_sched_wqueue_stop() has stopped it. + * + * This function is not necessary for 'conventional' startup. The scheduler is + * fully operational after drm_sched_init() succeeded. */ void drm_sched_wqueue_start(struct drm_gpu_scheduler *sched) {