linux-kernel - Re: [PATCH 1/2 RESEND] cpumask: Add for_each_cpu

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Date: Wed, 10 Apr 2024 09:26:08 +0200
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Kyle Meyer <kyle.meyer@....com>
Cc: linux-kernel@...r.kernel.org, yury.norov@...il.com, 
	andriy.shevchenko@...ux.intel.com, linux@...musvillemoes.dk, mingo@...hat.com, 
	peterz@...radead.org, juri.lelli@...hat.com, dietmar.eggemann@....com, 
	rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de, bristot@...hat.com, 
	vschneid@...hat.com, russ.anderson@....com, dimitri.sivanich@....com, 
	steve.wahl@....com
Subject: Re: [PATCH 1/2 RESEND] cpumask: Add for_each_cpu_from()

On Tue, 9 Apr 2024 at 17:54, Kyle Meyer <kyle.meyer@....com> wrote:
>
> Add for_each_cpu_from() as a generic cpumask macro.
>
> for_each_cpu_from() is the same as for_each_cpu(), except it starts at
> @cpu instead of zero.
>
> Signed-off-by: Kyle Meyer <kyle.meyer@....com>
> Acked-by: Yury Norov <yury.norov@...il.com>
> ---
>  include/linux/cpumask.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> index 1c29947db848..655211db38ff 100644
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -368,6 +368,16 @@ unsigned int __pure cpumask_next_wrap(int n, const struct cpumask *mask, int sta
>  #define for_each_cpu_or(cpu, mask1, mask2)                             \
>         for_each_or_bit(cpu, cpumask_bits(mask1), cpumask_bits(mask2), small_cpumask_bits)
>
> +/**
> + * for_each_cpu_from - iterate over every cpu present in @mask, starting at @cpu

So I was confused why you were not using for_each_cpu_wrap while
reading the description which has the same comment :
"
 * for_each_cpu_wrap - iterate over every cpu in a mask, starting at a
specified location
"
Could you clarify that it's not "every cpu present in @mask" but only
those after @cpu ?

> + * @cpu: the (optionally unsigned) integer iterator
> + * @mask: the cpumask pointer
> + *
> + * After the loop, cpu is >= nr_cpu_ids.
> + */
> +#define for_each_cpu_from(cpu, mask)                           \
> +       for_each_set_bit_from(cpu, cpumask_bits(mask), small_cpumask_bits)
> +
>  /**
>   * cpumask_any_but - return a "random" in a cpumask, but not this one.
>   * @mask: the cpumask to search
> --
> 2.44.0
>