linux-kernel - Re: [RFC PATCH 2/6] cpumask: Purify cpumask

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Message-ID: <20190525083207.GA102394@gmail.com>
Date:   Sat, 25 May 2019 10:32:07 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Nadav Amit <namit@...are.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [RFC PATCH 2/6] cpumask: Purify cpumask_next()


* Nadav Amit <namit@...are.com> wrote:

> cpumask_next() has no side-effects. Mark it as pure.
> 
> Cc: "David S. Miller" <davem@...emloft.net>
> Signed-off-by: Nadav Amit <namit@...are.com>
> ---
>  include/linux/cpumask.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> index 147bdec42215..20df46705f9c 100644
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -209,7 +209,7 @@ static inline unsigned int cpumask_last(const struct cpumask *srcp)
>  	return find_last_bit(cpumask_bits(srcp), nr_cpumask_bits);
>  }
>  
> -unsigned int cpumask_next(int n, const struct cpumask *srcp);
> +unsigned int __pure cpumask_next(int n, const struct cpumask *srcp);

I suppose this makes a code generation difference somewhere, right?

I'm wondering, couldn't it also be marked a const function? That's 
supposedly an even better category.

Thanks,

	Ingo