linux-kernel - Re: [PATCH 04/12] ia64: Replace cpu_down with freeze_secondary

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Date:   Tue, 19 Nov 2019 23:21:21 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Qais Yousef <qais.yousef@....com>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>, linux-ia64@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/12] ia64: Replace cpu_down with
 freeze_secondary_cpus

On Wed, 30 Oct 2019, Qais Yousef wrote:

> Use freeze_secondary_cpus() instead of open coding using cpu_down()
> directly.
> 
> This also prepares to make cpu_up/down a private interface for anything
> but the cpu subsystem.
> 
> Signed-off-by: Qais Yousef <qais.yousef@....com>
> CC: Tony Luck <tony.luck@...el.com>
> CC: Fenghua Yu <fenghua.yu@...el.com>
> CC: linux-ia64@...r.kernel.org
> CC: linux-kernel@...r.kernel.org
> ---
>  arch/ia64/kernel/process.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
> index 968b5f33e725..70b433eafa5c 100644
> --- a/arch/ia64/kernel/process.c
> +++ b/arch/ia64/kernel/process.c
> @@ -647,12 +647,8 @@ cpu_halt (void)
>  void machine_shutdown(void)
>  {
>  #ifdef CONFIG_HOTPLUG_CPU
> -	int cpu;
> -
> -	for_each_online_cpu(cpu) {
> -		if (cpu != smp_processor_id())
> -			cpu_down(cpu);
> -	}
> +	/* TODO: Can we use disable_nonboot_cpus()? */
> +	freeze_secondary_cpus(smp_processor_id());

freeze_secondary_cpus() is only available for CONFIG_PM_SLEEP_SMP=y and
disable_nonboot_cpus() is a NOOP for CONFIG_PM_SLEEP_SMP=n :)

Thanks,

	tglx