linux-kernel - Re: [PATCH 06/12] parisc: Replace cpu_up/down with device

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Message-ID: <20191120110933.wjtmpc4pmqmxhmma@e107158-lin.cambridge.arm.com>
Date:   Wed, 20 Nov 2019 11:09:34 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>
Cc:     Richard Fontana <rfontana@...hat.com>,
        Armijn Hemel <armijn@...ldur.nl>, linux-parisc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 06/12] parisc: Replace cpu_up/down with
 device_online/offline

On 10/30/19 15:38, Qais Yousef wrote:
> The core device API performs extra housekeeping bits that are missing
> from directly calling cpu_up/down.
> 
> See commit a6717c01ddc2 ("powerpc/rtas: use device model APIs and
> serialization during LPM") for an example description of what might go
> wrong.
> 
> 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: "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>
> CC: Helge Deller <deller@....de>
> CC: Richard Fontana <rfontana@...hat.com>
> CC: Armijn Hemel <armijn@...ldur.nl>
> CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> CC: Thomas Gleixner <tglx@...utronix.de>
> CC: linux-parisc@...r.kernel.org
> CC: linux-kernel@...r.kernel.org
> ---
> 
> Couldn't compile test this one.
> 
> I'm not confident that this is a correct patch to be honest. This __init
> indicates we're booting the secondary cpus and that might be too early in the
> process to use the core API..?

Helge, James

Do you have any comment on this? I have no means to test it and I'd
appreciate if you can spin it through one of your systems.

Thanks

--
Qais Yousef

> 
> 
>  arch/parisc/kernel/processor.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/parisc/kernel/processor.c b/arch/parisc/kernel/processor.c
> index 13f771f74ee3..4dde5fe78f0c 100644
> --- a/arch/parisc/kernel/processor.c
> +++ b/arch/parisc/kernel/processor.c
> @@ -212,7 +212,9 @@ static int __init processor_probe(struct parisc_device *dev)
>  #ifdef CONFIG_SMP
>  	if (cpuid) {
>  		set_cpu_present(cpuid, true);
> -		cpu_up(cpuid);
> +		lock_device_hotplug();
> +		device_online(get_cpu_device(cpuid));
> +		unlock_device_hotplug();
>  	}
>  #endif
>  
> -- 
> 2.17.1
>