Re: [RFC/PATCH] arm: do not skip SMP init calls on SMP_ON_UP case - Russell King

From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: nyushchenko@dev.rtsoft.ru
Cc: Will Deacon <will.deacon@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Rob Herring <robh@kernel.org>,
	Ian Campbell <ian.campbell@citrix.com>,
	Pavel Machek <pavel@ucw.cz>, Mason <slash.tmp@free.fr>,
	Paul Kocialkowski <contact@paulk.fr>,
	Masahiro Yamada <yamada.m@jp.panasonic.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, kuznetsovg@dev.rtsoft.ru
Subject: Re: [RFC/PATCH] arm: do not skip SMP init calls on SMP_ON_UP case
Date: Mon, 23 Nov 2015 12:03:18 +0000	[thread overview]
Message-ID: <20151123120317.GN8644@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <1448279946-19975-1-git-send-email-nyushchenko@dev.rtsoft.ru>

On Mon, Nov 23, 2015 at 02:59:06PM +0300, nyushchenko@dev.rtsoft.ru wrote:
> From: Nikita Yushchenko <nyushchenko@dev.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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