linux-kernel - Re: [PATCH v4 2/7] cpumask: Introduce for_each_cpu

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Date:   Tue, 27 Sep 2022 17:45:04 +0100
From:   Valentin Schneider <vschneid@...hat.com>
To:     Yury Norov <yury.norov@...il.com>
Cc:     netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mel Gorman <mgorman@...e.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Tony Luck <tony.luck@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Gal Pressman <gal@...dia.com>,
        Tariq Toukan <tariqt@...dia.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>
Subject: Re: [PATCH v4 2/7] cpumask: Introduce for_each_cpu_andnot()

On 25/09/22 08:23, Yury Norov wrote:
> On Fri, Sep 23, 2022 at 04:55:37PM +0100, Valentin Schneider wrote:
>> +/**
>> + * for_each_cpu_andnot - iterate over every cpu present in one mask, excluding
>> + *			 those present in another.
>> + * @cpu: the (optionally unsigned) integer iterator
>> + * @mask1: the first cpumask pointer
>> + * @mask2: the second cpumask pointer
>> + *
>> + * This saves a temporary CPU mask in many places.  It is equivalent to:
>> + *	struct cpumask tmp;
>> + *	cpumask_andnot(&tmp, &mask1, &mask2);
>> + *	for_each_cpu(cpu, &tmp)
>> + *		...
>> + *
>> + * After the loop, cpu is >= nr_cpu_ids.
>> + */
>> +#define for_each_cpu_andnot(cpu, mask1, mask2)				\
>> +	for ((cpu) = -1;						\
>> +		(cpu) = cpumask_next_andnot((cpu), (mask1), (mask2)),	\
>> +		(cpu) < nr_cpu_ids;)
>
> This would raise cpumaks_check() warning at the very last iteration.
> Because cpu is initialized insize the loop, you don't need to check it
> at all. You can do it like this:
>
>  #define for_each_cpu_andnot(cpu, mask1, mask2)				\
>          for_each_andnot_bit(...)
>
> Check this series for details (and please review).
> https://lore.kernel.org/all/20220919210559.1509179-8-yury.norov@gmail.com/T/
>

Thanks, I'll have a look.

> Thanks,
> Yury