linux-kernel - Re: [PATCH] RISC-V: Use a local variable instead of smp_processor

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Message-ID: <mhng-99e5afcf-d8c7-4660-a9e7-eb515e9aa55b@palmerdabbelt-glaptop1>
Date:   Thu, 25 Jun 2020 14:27:50 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     Atish Patra <Atish.Patra@....com>
CC:     linux-kernel@...r.kernel.org, greentime.hu@...ive.com,
        Atish Patra <Atish.Patra@....com>, aou@...s.berkeley.edu,
        anup@...infault.org, linux-riscv@...ts.infradead.org,
        Paul Walmsley <paul.walmsley@...ive.com>
Subject:     Re: [PATCH] RISC-V: Use a local variable instead of smp_processor_id()

On Mon, 22 Jun 2020 16:47:25 PDT (-0700), Atish Patra wrote:
> From: Greentime Hu <greentime.hu@...ive.com>
>
> Store the smp_processor_id() in a local variable to save some
> pointer chasing.
>
> Signed-off-by: Greentime Hu <greentime.hu@...ive.com>
> Signed-off-by: Atish Patra <atish.patra@....com>
> ---
>  arch/riscv/kernel/smpboot.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> index 4e9922790f6e..3e033e97dd08 100644
> --- a/arch/riscv/kernel/smpboot.c
> +++ b/arch/riscv/kernel/smpboot.c
> @@ -146,6 +146,7 @@ void __init smp_cpus_done(unsigned int max_cpus)
>  asmlinkage __visible void smp_callin(void)
>  {
>  	struct mm_struct *mm = &init_mm;
> +	unsigned int curr_cpuid = smp_processor_id();
>
>  	if (!IS_ENABLED(CONFIG_RISCV_SBI))
>  		clint_clear_ipi(cpuid_to_hartid_map(smp_processor_id()));
> @@ -155,9 +156,9 @@ asmlinkage __visible void smp_callin(void)
>  	current->active_mm = mm;
>
>  	trap_init();
> -	notify_cpu_starting(smp_processor_id());
> -	update_siblings_masks(smp_processor_id());
> -	set_cpu_online(smp_processor_id(), 1);
> +	notify_cpu_starting(curr_cpuid);
> +	update_siblings_masks(curr_cpuid);
> +	set_cpu_online(curr_cpuid, 1);
>  	/*
>  	 * Remote TLB flushes are ignored while the CPU is offline, so emit
>  	 * a local TLB flush right now just in case.

Thanks.  This is on for-next.