linux-kernel - Re: [PATCH] RISC-V: Fix /proc/cpuinfo cpumask warning

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Message-ID: <20221011182356.xbgvpoddhe4st6va@kamzik>
Date:   Tue, 11 Oct 2022 20:23:56 +0200
From:   Andrew Jones <ajones@...tanamicro.com>
To:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Yury Norov <yury.norov@...il.com>
Subject: Re: [PATCH] RISC-V: Fix /proc/cpuinfo cpumask warning


Boris pointed out on my x86 version of this patch that I didn't
give nearly enough information on why I sent it. Sorry about that!
I've tried to fill in some of that information in my reply to him
[1]. Sorry for lazily just pointing to that link here, but I'll
send a v2 with the information properly added tomorrow.

[1] https://lore.kernel.org/all/20221011181715.dpayrpjueha7kxoj@kamzik/

Thanks,
drew

On Tue, Oct 11, 2022 at 07:50:40PM +0200, Andrew Jones wrote:
> Upcoming cpumask changes will start issuing warnings[*] when cpu
> indices equal to nr_cpu_ids are passed to cpumask_next* functions.
> Ensure we don't generate a warning when reading /proc/cpuinfo by
> validating the cpu index before calling cpumask_next().
> 
> [*] Warnings will only appear with DEBUG_PER_CPU_MAPS enabled.
> 
> Signed-off-by: Andrew Jones <ajones@...tanamicro.com>
> Cc: Yury Norov <yury.norov@...il.com>
> ---
>  arch/riscv/kernel/cpu.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> index 4aa8cd749441..592ff065e09f 100644
> --- a/arch/riscv/kernel/cpu.c
> +++ b/arch/riscv/kernel/cpu.c
> @@ -166,9 +166,12 @@ static void print_mmu(struct seq_file *f)
>  
>  static void *c_start(struct seq_file *m, loff_t *pos)
>  {
> -	*pos = cpumask_next(*pos - 1, cpu_online_mask);
> -	if ((*pos) < nr_cpu_ids)
> -		return (void *)(uintptr_t)(1 + *pos);
> +	if (*pos < nr_cpu_ids) {
> +		*pos = cpumask_next(*pos - 1, cpu_online_mask);
> +		if (*pos < nr_cpu_ids)
> +			return (void *)(uintptr_t)(1 + *pos);
> +	}
> +
>  	return NULL;
>  }
>  
> -- 
> 2.37.3
>