linux-kernel - Re: [PATCH v8 2/2] ARM: Enable selection of SMP operations at boot time

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Message-ID: <20130425084933.GB12848@mudshark.cambridge.arm.com>
Date:	Thu, 25 Apr 2013 09:49:33 +0100
From:	Will Deacon <will.deacon@....com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"arnd@...db.de" <arnd@...db.de>,
	"nicolas.pitre@...aro.org" <nicolas.pitre@...aro.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"olof@...om.net" <olof@...om.net>, Jon Medhurst <tixy@...aro.org>
Subject: Re: [PATCH v8 2/2] ARM: Enable selection of SMP operations at boot
 time

On Wed, Apr 24, 2013 at 07:40:19PM +0100, Stefano Stabellini wrote:
> From: Jon Medhurst <tixy@...aro.org>
> 
> Add a new 'smp_init' hook to machine_desc so platforms can specify a
> function to be used to setup smp ops instead of having a statically
> defined value.  The hook must return true when smp_ops are initialized.
> If false the static mdesc->smp_ops will be used by default.
> 
> Signed-off-by: Jon Medhurst <tixy@...aro.org>
> Signed-off-by: Nicolas Pitre <nicolas.pitre@...aro.org>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> Reviewed-by: Santosh Shilimkar <santosh.shilimkar@...com>
> ---
>  arch/arm/include/asm/mach/arch.h |    4 ++++
>  arch/arm/kernel/setup.c          |   10 ++++++----
>  2 files changed, 10 insertions(+), 4 deletions(-)

[...]

>  	if (is_smp()) {
> -		if (psci_smp_available())
> -			smp_set_ops(&psci_smp_ops);
> -		else if (mdesc->smp)
> -			smp_set_ops(mdesc->smp);
> +		if (!mdesc->smp_init || !mdesc->smp_init()) {

Minor nit, but this feels backwards to me. We usually return 0 on success,
yet we're saying here that if mdesc->smp_init() returns 0, then we go and
override the smp ops.

Will

> +			if (psci_smp_available())
> +				smp_set_ops(&psci_smp_ops);
> +			else if (mdesc->smp)
> +				smp_set_ops(mdesc->smp);
> +		}
>  		smp_init_cpus();
>  	}
>  #endif
> -- 
> 1.7.2.5
> 
> 
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