linux-kernel - Re: [PATCH v3 04/15] arm: Don't use disable_nonboot

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Message-ID: <20200320110430.jozfyrqqx272266u@e107158-lin.cambridge.arm.com>
Date:   Fri, 20 Mar 2020 11:04:31 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     Russell King <linux@...linux.org.uk>
Cc:     "Paul E . McKenney" <paulmck@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v3 04/15] arm: Don't use disable_nonboot_cpus()

On 02/23/20 19:29, Qais Yousef wrote:
> disable_nonboot_cpus() is not safe to use when doing machine_down(),
> because it relies on freeze_secondary_cpus() which in turn is
> a suspend/resume related freeze and could abort if the logic detects any
> pending activities that can prevent finishing the offlining process.
> 
> Beside disable_nonboot_cpus() is dependent on CONFIG_PM_SLEEP_SMP which
> is an othogonal config to rely on to ensure this function works
> correctly.
> 
> Use `reboot_cpu` variable instead of hardcoding 0 as the reboot cpu.
> 
> Signed-off-by: Qais Yousef <qais.yousef@....com>
> CC: Russell King <linux@...linux.org.uk>
> CC: linux-arm-kernel@...ts.infradead.org
> CC: linux-kernel@...r.kernel.org
> ---

Hi Russel

Does the updated version look good to you now?

Thanks

--
Qais Yousef

>  arch/arm/kernel/reboot.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/kernel/reboot.c b/arch/arm/kernel/reboot.c
> index bb18ed0539f4..0ce388f15422 100644
> --- a/arch/arm/kernel/reboot.c
> +++ b/arch/arm/kernel/reboot.c
> @@ -88,11 +88,11 @@ void soft_restart(unsigned long addr)
>   * to execute e.g. a RAM-based pin loop is not sufficient. This allows the
>   * kexec'd kernel to use any and all RAM as it sees fit, without having to
>   * avoid any code or data used by any SW CPU pin loop. The CPU hotplug
> - * functionality embodied in disable_nonboot_cpus() to achieve this.
> + * functionality embodied in smp_shutdown_nonboot_cpus() to achieve this.
>   */
>  void machine_shutdown(void)
>  {
> -	disable_nonboot_cpus();
> +	smp_shutdown_nonboot_cpus(reboot_cpu);
>  }
>  
>  /*
> -- 
> 2.17.1
>