linux-kernel - Re: [PATCH] sched/dl : return accurate release rq lock info

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Date:   Fri, 5 Oct 2018 13:50:35 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peng Hao <peng.hao2@....com.cn>
Cc:     mingo@...hat.com, peterz@...radead.org,
        andrea.parri@...rulasolutions.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH]  sched/dl : return accurate release rq lock info

On Sat, 6 Oct 2018 09:08:37 +0800
Peng Hao <peng.hao2@....com.cn> wrote:

> find_lock_later_rq may or not releease rq lock when return
> later_rq=NULL, but it is fuzzy.
> If not releasing rq lock, it is unnecessary to re-call
> pick_next_pushable_dl_task.
> 
> Signed-off-by: Peng Hao <peng.hao2@....com.cn>


Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve

> ---
>  kernel/sched/deadline.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 997ea7b..8e875ec 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1979,7 +1979,7 @@ static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
>  				     !dl_task(task) ||
>  				     !task_on_rq_queued(task))) {
>  				double_unlock_balance(rq, later_rq);
> -				later_rq = NULL;
> +				later_rq = RETRY_TASK;
>  				break;
>  			}
>  		}
> @@ -2063,7 +2063,9 @@ static int push_dl_task(struct rq *rq)
>  
>  	/* Will lock the rq it'll find */
>  	later_rq = find_lock_later_rq(next_task, rq);
> -	if (!later_rq) {
> +	if (!later_rq)
> +		goto out;
> +	if (later_rq == RETRY_TASK) {
>  		struct task_struct *task;
>  
>  		/*