linux-kernel - Re: [PATCH v2 03/14] arm: arm64: Don't use disable_nonboot

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Message-ID: <20200121165030.xksivf6mrhsaynq2@e107158-lin.cambridge.arm.com>
Date:   Tue, 21 Jan 2020 16:50:31 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 03/14] arm: arm64: Don't use disable_nonboot_cpus()

On 11/25/19 11:27, Qais Yousef wrote:
> disable_nonboot_cpus() is not safe to use when doing machine_down(),
> because it relies on freeze_secondary_cpus() which in return 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.
> 
> Signed-off-by: Qais Yousef <qais.yousef@....com>
> CC: Russell King <linux@...linux.org.uk>
> CC: Catalin Marinas <catalin.marinas@....com>
> CC: Will Deacon <will@...nel.org>
> CC: linux-arm-kernel@...ts.infradead.org
> CC: linux-kernel@...r.kernel.org
> ---

Ping :)

I'm missing ACKs on this patch and patch 4 for arm64. Hopefully none should be
controversial.

Thanks!

--
Qais Yousef

>  arch/arm/kernel/reboot.c    | 4 ++--
>  arch/arm64/kernel/process.c | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/kernel/reboot.c b/arch/arm/kernel/reboot.c
> index bb18ed0539f4..58ad1a70f770 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(0);
>  }
>  
>  /*
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 71f788cd2b18..3bcc9bfc581e 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -141,11 +141,11 @@ void arch_cpu_idle_dead(void)
>   * 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 smpt_shutdown_nonboot_cpus() to achieve this.
>   */
>  void machine_shutdown(void)
>  {
> -	disable_nonboot_cpus();
> +	smp_shutdown_nonboot_cpus(0);
>  }
>  
>  /*
> -- 
> 2.17.1
>