Re: [PATCH 12/24] sched/fair: Prepare exit/cleanup paths for delayed_dequeue

Valentin Schneider
2024-08-13T12:43:53Z

On 27/07/24 12:27, Peter Zijlstra wrote:
> @@ -12817,10 +12830,26 @@ static void attach_task_cfs_rq(struct ta
> static void switched_from_fair(struct rq *rq, struct task_struct *p)
> {
> detach_task_cfs_rq(p);
> + /*
> + * Since this is called after changing class, this isn't quite right.
> + * Specifically, this causes the task to get queued in the target class
> + * and experience a 'spurious' wakeup.
> + *
> + * However, since 'spurious' wakeups are harmless, this shouldn't be a
> + * problem.
> + */
> + p->se.sched_delayed = 0;
> + /*
> + * While here, also clear the vlag, it makes little sense to carry that
> + * over the excursion into the new class.
> + */
> + p->se.vlag = 0;

RQ lock is held, the task can't be current if it's ->sched_delayed; is a
dequeue_task() not possible at this point? Or just not worth it?