Re: [PATCH 1/4] cpumask: relax cpumask_any_but()

Reinette Chatre
2025-04-23T21:28:17Z

Hi Yury,

On 4/7/25 8:38 AM, Yury Norov wrote:
> From: Yury Norov [NVIDIA] <yury.norov@gmail.com>
>
> Similarly to other cpumask search functions, accept -1, and consider
> it as 'any cpu' hint. This helps users to avoid coding special cases.
>
> Signed-off-by: Yury Norov [NVIDIA] <yury.norov@gmail.com>
> ---
> include/linux/cpumask.h | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> index beff4d26e605..0f816092c891 100644
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -413,6 +413,7 @@ unsigned int cpumask_next_wrap(int n, const struct cpumask *src)
> * @cpu: the cpu to ignore.
> *
> * Often used to find any cpu but smp_processor_id() in a mask.
> + * If @cpu == -1, the function is equivalent to cpumask_any().

Now that -1 is a legal argument, should the "cpu" parameter be of "int" type (instead of
"unsigned int")?

> * Return: >= nr_cpu_ids if no cpus set.
> */
> static __always_inline
> @@ -420,7 +421,10 @@ unsigned int cpumask_any_but(const struct cpumask *mask, unsigned int cpu)
> {
> unsigned int i;
>
> - cpumask_check(cpu);
> + /* -1 is a legal arg here. */
> + if (cpu != -1)
> + cpumask_check(cpu);
> +
> for_each_cpu(i, mask)
> if (i != cpu)
> break;
> @@ -433,6 +437,7 @@ unsigned int cpumask_any_but(const struct cpumask *mask, unsigned int cpu)
> * @mask2: the second input cpumask
> * @cpu: the cpu to ignore
> *
> + * If @cpu == -1, the function is equivalent to cpumask_any_and().
> * Returns >= nr_cpu_ids if no cpus set.
> */
> static __always_inline
> @@ -442,7 +447,10 @@ unsigned int cpumask_any_and_but(const struct cpumask *mask1,

Same question here regarding type of "cpu" parameter.

> {
> unsigned int i;
>
> - cpumask_check(cpu);
> + /* -1 is a legal arg here. */
> + if (cpu != -1)
> + cpumask_check(cpu);
> +
> i = cpumask_first_and(mask1, mask2);
> if (i != cpu)
> return i;

Reinette