linux-kernel - Re: [PATCH] sched/fair: remove the spin

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Date:   Fri, 30 Oct 2020 11:48:00 -0700
From:   Benjamin Segall <bsegall@...gle.com>
To:     Hui Su <sh_def@....com>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, mgorman@...e.de, bristot@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/fair: remove the spin_lock operations

Hui Su <sh_def@....com> writes:

> Since 'ab93a4bc955b ("sched/fair: Remove
> distribute_running fromCFS bandwidth")',there is
> nothing to protect between raw_spin_lock_irqsave/store()
> in do_sched_cfs_slack_timer().
>
> So remove it.

Reviewed-by: Ben Segall <bsegall@...gle.com>

(I might nitpick the subject to be clear that it should be trivial
because the lock area is empty, or call them dead or something, but it's
not all that important)

>
> Signed-off-by: Hui Su <sh_def@....com>
> ---
>  kernel/sched/fair.c | 3 ---
>  1 file changed, 3 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 290f9e38378c..5ecbf5e63198 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5105,9 +5105,6 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
>  		return;
>  
>  	distribute_cfs_runtime(cfs_b);
> -
> -	raw_spin_lock_irqsave(&cfs_b->lock, flags);
> -	raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
>  }
>  
>  /*