linux-kernel - Re: [PATCH 3/4] cpumask: add cpumask_{first,next}

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Message-ID: <c96bade5-200a-4812-8df6-d6dcf2984a01@intel.com>
Date: Wed, 23 Apr 2025 14:28:38 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Yury Norov <yury.norov@...il.com>, Tony Luck <tony.luck@...el.com>,
	"Thomas Gleixner" <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	"Borislav Petkov" <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, Rasmus Villemoes
	<linux@...musvillemoes.dk>, <x86@...nel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] cpumask: add cpumask_{first,next}_andnot() API

Hi Yury,

On 4/7/25 8:38 AM, Yury Norov wrote:

...

> @@ -284,6 +297,25 @@ unsigned int cpumask_next_and(int n, const struct cpumask *src1p,
>  		small_cpumask_bits, n + 1);
>  }
>  
> +/**
> + * cpumask_next_andnot - get the next cpu in *src1p & ~*src2p
> + * @n: the cpu prior to the place to search (i.e. return will be > @n)
> + * @src1p: the first cpumask pointer
> + * @src2p: the second cpumask pointer
> + *
> + * Return: >= nr_cpu_ids if no further cpus set in both.
> + */
> +static __always_inline
> +unsigned int cpumask_next_andnot(int n, const struct cpumask *src1p,
> +				 const struct cpumask *src2p)

Looks like the custom followed here is to name parameter that can have
-1 as value "n" and let it have type "int". Should this also apply to
cpumask_andnot_any_but(), cpumask_any_but(), and cpumask_any_and_but()
modified/introduced in this series?

> +{
> +	/* -1 is a legal arg here. */
> +	if (n != -1)
> +		cpumask_check(n);
> +	return find_next_andnot_bit(cpumask_bits(src1p), cpumask_bits(src2p),
> +		small_cpumask_bits, n + 1);
> +}
> +
>  /**
>   * cpumask_next_and_wrap - get the next cpu in *src1p & *src2p, starting from
>   *			   @n+1. If nothing found, wrap around and start from
> @@ -458,6 +490,33 @@ unsigned int cpumask_any_and_but(const struct cpumask *mask1,
>  	return cpumask_next_and(cpu, mask1, mask2);
>  }
>  
> +/**
> + * cpumask_andnot_any_but - pick an arbitrary cpu from *mask1 & ~*mask2, but not this one.
> + * @mask1: the first input cpumask
> + * @mask2: the second input cpumask
> + * @cpu: the cpu to ignore
> + *
> + * If @cpu == -1, the function returns the first matching cpu.
> + * Returns >= nr_cpu_ids if no cpus set.
> + */
> +static __always_inline
> +unsigned int cpumask_andnot_any_but(const struct cpumask *mask1,
> +				    const struct cpumask *mask2,
> +				    unsigned int cpu)

Since -1 is legal argument I expect "cpu" to be int.

> +{
> +	unsigned int i;
> +
> +	/* -1 is a legal arg here. */
> +	if (cpu != -1)
> +		cpumask_check(cpu);
> +
> +	i = cpumask_first_andnot(mask1, mask2);
> +	if (i != cpu)
> +		return i;
> +
> +	return cpumask_next_andnot(cpu, mask1, mask2);
> +}
> +
>  /**
>   * cpumask_nth - get the Nth cpu in a cpumask
>   * @srcp: the cpumask pointer

Reinette