Re: [PATCH 07/18] sched/fair: Add push task mechanism for fair

[Kayra Cizmeci]

On Fri, Oct 02, 2026 at 05:44:04PM +0200, Vincent Guittot wrote:
> +static void __fair_add_pushable_task(struct rq *rq, struct task_struct *p)
> +{
> +	plist_del(&p->pushable_tasks, &rq->cfs.pushable_tasks);
> +	plist_node_init(&p->pushable_tasks, p->prio);
> +	plist_add(&p->pushable_tasks, &rq->cfs.pushable_tasks);
> +}
> +
> +static void fair_add_pushable_prev(struct rq *rq, struct task_struct *prev, struct task_struct *next)
> +{
> +	if (sched_push_task_enabled() && fair_check_pushable_task(rq, prev, next))
> +		__fair_add_pushable_task(rq, prev);
> +}
> +
>  /*
>   * select_task_rq_fair: Select a target runqueue for the task.
>   * There are 2 ways to select the target runqueue:
> @@ -10272,6 +10426,12 @@ static void put_prev_task_fair(struct rq *rq, struct task_struct *prev, struct t
>  	cfs_rq->curr = NULL;
>  	if (se->on_rq)
>  		__enqueue_entity(cfs_rq, se);
> +
> +	/*
> +	 * The previous task might be eligible for being pushed on another cpu
> +	 * if it is still active.
> +	 */
> +	fair_add_pushable_prev(rq, prev, next);
>  }
>  
>  /*



Re-reviewed this :-)

On our rq, we have a fair task TA that holds M mutex. we have a RT task TB blocked on M. 
we enter __schedule() and from there pick_next_task(). it chooses TB as next, but it adds 
TA to the pushable task list. then we enter the proxy exec path. 
donor is set to TB. but when we enter find_proxy_task(), next is changed to
TA. so right now, TA is on the push list even if its still curr.

(With the whole series applied.)

Am I missing something? Should curr not be pushed?

Thanks,


Kayra