On Tue, 2025-10-28 at 12:43 -0700, Matthew Brost wrote: > On Tue, Oct 28, 2025 at 02:46:02PM +0100, Philipp Stanner wrote: > > If a job from a ready entity needs more credits than are currently > > available, drm_sched_run_job_work() (a work item) simply returns and > > doesn't reschedule itself. 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 <[email protected]> > > --- > > 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.
Sounds correct to me. We can still merge #1, though, for a bit more clearness. P.
