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The scheduler is only woken up again when the > next job gets pushed with drm_sched_entity_push_job(). > > If someone submits a job that needs too many credits and doesn't submit > more jobs afterwards, this would lead to the scheduler never pulling the > too-expensive job, effectively hanging forever. > > Document this problem as a FIXME. > > Signed-off-by: Philipp Stanner > --- > drivers/gpu/drm/scheduler/sched_main.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c > index 492e8af639db..eaf8d17b2a66 100644 > --- a/drivers/gpu/drm/scheduler/sched_main.c > +++ b/drivers/gpu/drm/scheduler/sched_main.c > @@ -1237,6 +1237,16 @@ static void drm_sched_run_job_work(struct work_struct *w) > > /* Find entity with a ready job */ > entity = drm_sched_select_entity(sched); > + /* > + * FIXME: > + * The entity can be NULL when the scheduler currently has no capacity > + * (credits) for more jobs. If that happens, the work item terminates > + * itself here, without rescheduling itself. > + * > + * It only gets started again in drm_sched_entity_push_job(). IOW, the > + * scheduler might hang forever if a job that needs too many credits > + * gets submitted to an entity and no other, subsequent jobs are. > + */ drm_sched_job_done frees the credits, which triggers drm_sched_free_job_work, and that in turn triggers drm_sched_run_job_work. This flow could be refined a bit, but I do believe it works—unless I'm missing something. I'm pretty sure we have tests in Xe that exhaust the credits, though it might be continuous submissions; I'd have to check. Matt > if (!entity) { > /* > * Either no more work to do, or the next ready job needs more > -- > 2.49.0 >