linux-kernel - Re: [PATCH] cpu/hotplug: simplify access percpu cpuhp

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Date:   Tue, 25 May 2021 11:19:27 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Yuan ZhaoXiong <yuanzhaoxiong@...du.com>, peterz@...radead.org,
        vincent.donnefort@....com, mingo@...nel.org, bristot@...hat.com,
        npiggin@...il.com, tglx@...utronix.de
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpu/hotplug: simplify access percpu cpuhp_state

On 23/05/21 21:31, Yuan ZhaoXiong wrote:
> It is unnecessary to invoke per_cpu_ptr() function everytime to access
> percpu cpuhp_state and use the variable st instead.
>
> Signed-off-by: Yuan ZhaoXiong <yuanzhaoxiong@...du.com>

Reviewed-by: Valentin Schneider <valentin.schneider@....com>

> ---
>  kernel/cpu.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index e538518..2942cb4 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -961,7 +961,7 @@ static int takedown_cpu(unsigned int cpu)
>       int err;
>
>       /* Park the smpboot threads */
> -	kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
> +	kthread_park(st->thread);
>
>       /*
>        * Prevent irq alloc/free while the dying cpu reorganizes the
> @@ -977,7 +977,7 @@ static int takedown_cpu(unsigned int cpu)
>               /* CPU refused to die */
>               irq_unlock_sparse();
>               /* Unpark the hotplug thread so we can rollback there */
> -		kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
> +		kthread_unpark(st->thread);
>               return err;
>       }
>       BUG_ON(cpu_online(cpu));
> --
> 1.7.1