linux-kernel - Re: [PATCH 07/22] mm/vmstat: Drop get_online_cpus() from init_cpu_node_state/vmstat_cpu

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Message-ID: <20161128092415.GB14835@dhcp22.suse.cz>
Date:   Mon, 28 Nov 2016 10:24:17 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, rt@...utronix.de, tglx@...utronix.de,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org
Subject: Re: [PATCH 07/22] mm/vmstat: Drop get_online_cpus() from
 init_cpu_node_state/vmstat_cpu_dead()

On Sun 27-11-16 00:13:35, Sebastian Andrzej Siewior wrote:
> Both functions are called with protection against cpu hotplug already so
> *_online_cpus() could be dropped.
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: linux-mm@...ck.org
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  mm/vmstat.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 604f26a4f696..0b63ffb5c407 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1722,24 +1722,19 @@ static void __init init_cpu_node_state(void)
>  {
>  	int cpu;
>  
> -	get_online_cpus();
>  	for_each_online_cpu(cpu)
>  		node_set_state(cpu_to_node(cpu), N_CPU);
> -	put_online_cpus();
>  }
>  
>  static void vmstat_cpu_dead(int node)
>  {
>  	int cpu;
>  
> -	get_online_cpus();
>  	for_each_online_cpu(cpu)
>  		if (cpu_to_node(cpu) == node)
> -			goto end;
> +			return;
>  
>  	node_clear_state(node, N_CPU);
> -end:
> -	put_online_cpus();
>  }
>  
>  /*
> -- 
> 2.10.2
> 
> --
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-- 
Michal Hocko
SUSE Labs