linux-kernel - Re: [PATCH] cpu: mark cpu_possible_mask as __ro_after

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Message-ID: <a1fafb71-cbd9-4d0b-8c3c-2b69be97db3e@roeck-us.net>
Date: Wed, 21 Feb 2024 22:00:26 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Alexey Dobriyan <adobriyan@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpu: mark cpu_possible_mask as __ro_after_init

On Mon, Feb 05, 2024 at 01:01:19PM +0300, Alexey Dobriyan wrote:
> cpu_possible_mask is by definition "cpus which could be hotplugged
> without reboot" -- property which is fixed after kernel enumerates
> motheboard capabilities and hardware configuration.
> 
> Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
> ---
> 
>  kernel/cpu.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -3107,10 +3107,10 @@ const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
>  EXPORT_SYMBOL(cpu_all_bits);
>  
>  #ifdef CONFIG_INIT_ALL_POSSIBLE
> -struct cpumask __cpu_possible_mask __read_mostly
> +struct cpumask __cpu_possible_mask __ro_after_init;
>  	= {CPU_BITS_ALL};

I guess you didn't compile test this code.

Guenter

>  #else
> -struct cpumask __cpu_possible_mask __read_mostly;
> +struct cpumask __cpu_possible_mask __ro_after_init;
>  #endif
>  EXPORT_SYMBOL(__cpu_possible_mask);
>