linux-kernel - Re: [RFC/PATCH] arm: do not skip SMP init calls on SMP_ON

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Message-ID: <20151123120317.GN8644@n2100.arm.linux.org.uk>
Date:	Mon, 23 Nov 2015 12:03:18 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	nyushchenko@....rtsoft.ru
Cc:	Will Deacon <will.deacon@....com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Rob Herring <robh@...nel.org>,
	Ian Campbell <ian.campbell@...rix.com>,
	Pavel Machek <pavel@....cz>, Mason <slash.tmp@...e.fr>,
	Paul Kocialkowski <contact@...lk.fr>,
	Masahiro Yamada <yamada.m@...panasonic.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kuznetsovg@....rtsoft.ru
Subject: Re: [RFC/PATCH] arm: do not skip SMP init calls on SMP_ON_UP case

On Mon, Nov 23, 2015 at 02:59:06PM +0300, nyushchenko@....rtsoft.ru wrote:
> From: Nikita Yushchenko <nyushchenko@....rtsoft.ru>
> 
> While running an imx6s boasrd, I got following message in boot log:
> 
> [    0.032414] CPU1: failed to boot: -38
> 
> This looked strange: imx6s is singe-core and kernel perfectly knows
> that. However, for some reason it tries to initialize CPU 1?
> 
> I found this to be caused by
> - CONFIG_SMP_ON_UP successfully detects that system is single core,
> - this causes is_smp() to return false,
> - this causes setup_arch() to skip smp_init_cpus() call,
> - this skips board-specific code that sets cpu_possible mask.

Right, so you should end up with the possible and present masks
containing just one CPU, which should prevent the kernel trying to
bring any secondary CPUs online.

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