linux-kernel - Re: [PATCH] x86: remove the useless branch in c

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Date:	Wed, 26 Sep 2012 11:43:52 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	Michael Wang <wangyun@...ux.vnet.ibm.com>
CC:	linux-kernel@...r.kernel.org, x86@...nel.org,
	kjwinchester@...il.com, borislav.petkov@....com,
	ak@...ux.intel.com, hpa@...or.com, mingo@...hat.com,
	tglx@...utronix.de
Subject: Re: [PATCH] x86: remove the useless branch in c_start()

On 09/19/2012 01:42 PM, Michael Wang wrote:
> Since 'cpu == -1' in cpumask_next() is legal, no need to handle '*pos == 0'
> specially.
> 
> About the comments:
> 	/* just in case, cpu 0 is not the first */
> A test with a cpumask in which cpu 0 is not the first has been done, and it
> works well.

Could I get some comments on this patch?

Regards,
Michael Wang

> 
> This patch will remove that useless branch to clean the code.
> 
> Signed-off-by: Michael Wang <wangyun@...ux.vnet.ibm.com>
> ---
>  arch/x86/kernel/cpu/proc.c |    5 +----
>  1 files changed, 1 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
> index 8022c66..fbd8955 100644
> --- a/arch/x86/kernel/cpu/proc.c
> +++ b/arch/x86/kernel/cpu/proc.c
> @@ -140,10 +140,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
> 
>  static void *c_start(struct seq_file *m, loff_t *pos)
>  {
> -	if (*pos == 0)	/* just in case, cpu 0 is not the first */
> -		*pos = cpumask_first(cpu_online_mask);
> -	else
> -		*pos = cpumask_next(*pos - 1, cpu_online_mask);
> +	*pos = cpumask_next(*pos - 1, cpu_online_mask);
>  	if ((*pos) < nr_cpu_ids)
>  		return &cpu_data(*pos);
>  	return NULL;
> 

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