linux-kernel - Re: [PATCH] sched: rename __prepare_to_swait() to add_swait_queue

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Date:   Wed, 17 Mar 2021 06:12:41 +0100
From:   Mike Galbraith <efault@....de>
To:     Wang Qing <wangqing@...o.com>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: rename __prepare_to_swait() to
 add_swait_queue_locked()

On Tue, 2021-03-16 at 19:59 +0800, Wang Qing wrote:
> This function just puts wait into queue, and does not do an operation similar
> to prepare_to_wait() in wait.c.
> And during the operation, the caller needs to hold the lock to protect.

I see zero benefit to churn like this.  You're taking a dinky little
file that's perfectly clear (and pretty), and restating the obvious.

>
> Signed-off-by: Wang Qing <wangqing@...o.com>
> ---
>  kernel/sched/completion.c | 2 +-
>  kernel/sched/sched.h      | 2 +-
>  kernel/sched/swait.c      | 6 +++---
>  3 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/sched/completion.c b/kernel/sched/completion.c
> index a778554..3d28a5a
> --- a/kernel/sched/completion.c
> +++ b/kernel/sched/completion.c
> @@ -79,7 +79,7 @@ do_wait_for_common(struct completion *x,
>  				timeout = -ERESTARTSYS;
>  				break;
>  			}
> -			__prepare_to_swait(&x->wait, &wait);
> +			add_swait_queue_locked(&x->wait, &wait);
>  			__set_current_state(state);
>  			raw_spin_unlock_irq(&x->wait.lock);
>  			timeout = action(timeout);
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 10a1522..0516f50
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2719,4 +2719,4 @@ static inline bool is_per_cpu_kthread(struct task_struct *p)
>  #endif
>
>  void swake_up_all_locked(struct swait_queue_head *q);
> -void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait);
> +void add_swait_queue_locked(struct swait_queue_head *q, struct swait_queue *wait);
> diff --git a/kernel/sched/swait.c b/kernel/sched/swait.c
> index 7a24925..f48a544
> --- a/kernel/sched/swait.c
> +++ b/kernel/sched/swait.c
> @@ -82,7 +82,7 @@ void swake_up_all(struct swait_queue_head *q)
>  }
>  EXPORT_SYMBOL(swake_up_all);
>
> -void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
> +void add_swait_queue_locked(struct swait_queue_head *q, struct swait_queue *wait)
>  {
>  	wait->task = current;
>  	if (list_empty(&wait->task_list))
> @@ -94,7 +94,7 @@ void prepare_to_swait_exclusive(struct swait_queue_head *q, struct swait_queue *
>  	unsigned long flags;
>
>  	raw_spin_lock_irqsave(&q->lock, flags);
> -	__prepare_to_swait(q, wait);
> +	add_swait_queue_locked(q, wait);
>  	set_current_state(state);
>  	raw_spin_unlock_irqrestore(&q->lock, flags);
>  }
> @@ -114,7 +114,7 @@ long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait
>  		list_del_init(&wait->task_list);
>  		ret = -ERESTARTSYS;
>  	} else {
> -		__prepare_to_swait(q, wait);
> +		add_swait_queue_locked(q, wait);
>  		set_current_state(state);
>  	}
>  	raw_spin_unlock_irqrestore(&q->lock, flags);