Re: [PATCH 08/18] sched: Introduce WF_ON_RQ wake flag

[Peter Zijlstra]

On Wed, Sep 16, 2026 at 03:57:54PM +0530, K Prateek Nayak wrote:

> > @@ -2393,8 +2393,8 @@ unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state
> >  		 * If task is sched_delayed, force dequeue it, to avoid always
> >  		 * hitting the tick timeout in the queued case
> >  		 */
> > -		if (p->se.sched_delayed)
> > -			dequeue_task(rq, p, DEQUEUE_SLEEP | DEQUEUE_DELAYED);
> > +		if (p->is_blocked)
> > +			dequeue_task(rq, p, DEQUEUE_SLEEP | DEQUEUE_BLOCKED);
> 
> For proxy donors, this will simply dequeue the task without
> transitioning p->on_rq to 0.
> 
> If we want to break proxy at this point, maybe we want to bring
> that __block_task() into dequeue task and do it for
> DEQUEUE_BLOCKED?
> 
> >  		trace_sched_wait_task(p);
> >  		running = task_on_cpu(rq, p);
> >  		queued = task_on_rq_queued(p);
> > @@ -3889,8 +3889,7 @@ static int ttwu_runnable(struct task_struct *p, int wake_flags)
> >  
> >  	update_rq_clock(rq);
> >  	if (p->is_blocked) {
> > -		if (p->se.sched_delayed)
> > -			enqueue_task(rq, p, ENQUEUE_NOCLOCK | ENQUEUE_DELAYED);
> > +		enqueue_task(rq, p, ENQUEUE_NOCLOCK | ENQUEUE_BLOCKED);
> 
> For proxy donors on rq that don't belong to fair, this will enqueue
> an already enqueued task.

For both the idea would be that {EN,DE}QUEUE_BLOCKED would be ignored
when inappropriate.

Eg. fair will no-op when !sched_delayed.

I did mention none of the other classes behave properly in this regard,
although the note was perhaps a little cryptic.