On Mon, May 06, 2019 at 06:48:33AM +0200, Luca Abeni wrote:
> @@ -1223,8 +1250,17 @@ static void update_curr_dl(struct rq *rq)
> dl_se->dl_overrun = 1;
>
> __dequeue_task_dl(rq, curr, 0);
> - if (unlikely(dl_se->dl_boosted || !start_dl_timer(curr)))
> + if (unlikely(dl_se->dl_boosted || !start_dl_timer(curr))) {
> enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
> +#ifdef CONFIG_SMP
> + } else if (dl_se->dl_adjust) {
> + if (rq->migrating_task == NULL) {
> + queue_balance_callback(rq,
> &per_cpu(dl_migrate_head, rq->cpu), migrate_dl_task);
I'm not entirely sure about this one.
That is, we only do those callbacks from:
schedule_tail()
__schedule()
rt_mutex_setprio()
__sched_setscheduler()
and the above looks like it can happen outside of those.
The pattern in those sites is:
rq_lock();
... do crap that leads to queue_balance_callback()
rq_unlock()
if (rq->balance_callback) {
raw_spin_lock_irqsave(rq->lock, flags);
... do callbacks
raw_spin_unlock_irqrestore(rq->lock, flags);
}
So I suppose can catch abuse of this API by doing something like the
below; can you validate?
---
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index aaca0e743776..89e615f1eae6 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1134,6 +1134,14 @@ static inline void rq_pin_lock(struct rq *rq, struct
rq_flags *rf)
rf->cookie = lockdep_pin_lock(&rq->lock);
#ifdef CONFIG_SCHED_DEBUG
+#ifdef CONFIG_SMP
+ /*
+ * There should not be pending callbacks at the start of rq_lock();
+ * all sites that handle them flush them at the end.
+ */
+ WARN_ON_ONCE(rq->balance_callback);
+#endif
+
rq->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP);
rf->clock_update_flags = 0;
#endif
