linux-kernel - Re: [PATCH v2 5/6] powerpc/smp: Add read

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Message-ID: <87mswf5i8j.fsf@mail.lhotse>
Date:   Thu, 19 Oct 2023 15:49:48 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Nicholas Piggin <npiggin@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rohan McLure <rmclure@...ux.ibm.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        "ndesaulniers@...gle.com" <ndesaulniers@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/6] powerpc/smp: Add read_mostly attribute

Srikar Dronamraju <srikar@...ux.vnet.ibm.com> writes:
> There are some variables that are only updated at boot time.
> So add read_mostly attribute to such variables

If they're only updated at boot time then __ro_after_init would be the
better annotation.

cheers

> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 29da9262cb17..b1eb11a66902 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -77,10 +77,10 @@ static DEFINE_PER_CPU(int, cpu_state) = { 0 };
>  #endif
>  
>  struct task_struct *secondary_current;
> -bool has_big_cores;
> -bool coregroup_enabled;
> -bool thread_group_shares_l2;
> -bool thread_group_shares_l3;
> +bool has_big_cores __read_mostly;
> +bool coregroup_enabled __read_mostly;
> +bool thread_group_shares_l2 __read_mostly;
> +bool thread_group_shares_l3 __read_mostly;
>  
>  DEFINE_PER_CPU(cpumask_var_t, cpu_sibling_map);
>  DEFINE_PER_CPU(cpumask_var_t, cpu_smallcore_map);
> @@ -987,7 +987,7 @@ static int __init init_thread_group_cache_map(int cpu, int cache_property)
>  	return 0;
>  }
>  
> -static bool shared_caches;
> +static bool shared_caches __read_mostly;
>  DEFINE_STATIC_KEY_FALSE(powerpc_asym_packing);
>  
>  #ifdef CONFIG_SCHED_SMT
> -- 
> 2.31.1