linux-kernel - Re: [PATCH 2/2] Use num_possible_cpus() instead of direct use of NR

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Message-ID: <5693B22E.3070409@suse.cz>
Date:	Mon, 11 Jan 2016 14:46:22 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Ameen <ameenali023@...il.com>, mingo@...nel.org,
	peterz@...radead.org, mhocko@...e.com
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] Use num_possible_cpus() instead of direct use of
 NR_CPUS.

On 01/10/2016 04:13 PM, Ameen wrote:
> WARNING: usage of NR_CPUS is often wrong - consider using cpu_possible(), num_possible_cpus()..

Is that a checkpatch warning? Notice the word "often". You need to provide info
why it's the case here (and I doubt the change will be corect in this case).

> Signed-off-by : Ameen Ali <Ameenali023@...il.com>
> ---
>  kernel/smp.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/smp.c b/kernel/smp.c
> index d903c02..94033ac 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -549,13 +549,13 @@ static int __init maxcpus(char *str)
>  early_param("maxcpus", maxcpus);
>  
>  /* Setup number of possible processor ids */
> -int nr_cpu_ids __read_mostly = NR_CPUS;
> +int nr_cpu_ids __read_mostly = num_possible_cpus();
>  EXPORT_SYMBOL(nr_cpu_ids);
>  
>  /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
>  void __init setup_nr_cpu_ids(void)
>  {
> -	nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
> +	nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),num_possible_cpus()) + 1;
>  }
>  
>  void __weak smp_announce(void)
>