Re: [RFC][PATCH 2/4] sched: Push put_prev_task() into pick_next_task()

[Michael Wang <wangyun@linux.vnet.ibm.com>]

> +pick_next_task_fair(struct rq *rq, struct task_struct *prev)
>  {
>  	struct task_struct *p;
>  	struct cfs_rq *cfs_rq = &rq->cfs;
> @@ -2999,6 +3000,9 @@ static struct task_struct *pick_next_tas
>  	if (!cfs_rq->nr_running)
>  		return NULL;
> 
> +	if (prev)
> +		prev->sched_class->put_prev_task(rq, prev);
> +
>  	do {
>  		se = pick_next_entity(cfs_rq);
>  		set_next_entity(cfs_rq, se);
> --- a/kernel/sched/idle_task.c
> +++ b/kernel/sched/idle_task.c
> @@ -22,8 +22,12 @@ static void check_preempt_curr_idle(stru
>  	resched_task(rq->idle);
>  }

Will it cause trouble when the last task on cfs_rq was dequeued before
been putted?

The cfs_rq->nr_running will be 0 and we will miss the chance to put
prev, will we?

Regards,
Michael Wang