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

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Date: Thu, 22 Feb 2024 13:26:44 +0300
From: Alexey Dobriyan <adobriyan@...il.com>
To: Guenter Roeck <linux@...ck-us.net>
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 Wed, Feb 21, 2024 at 10:00:26PM -0800, Guenter Roeck wrote:
> 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.

On parisc, no. Oh well.

> >  #else
> > -struct cpumask __cpu_possible_mask __read_mostly;
> > +struct cpumask __cpu_possible_mask __ro_after_init;