From mboxrd@z Thu Jan  1 00:00:00 1970
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
Date: Fri, 13 Feb 2015 22:58:54 +0000
Subject: Re: [PATCH v2] ARM: smp: Only expose /sys/.../cpuX/online if hotpluggable
Message-Id: <20150213225854.GG8656@n2100.arm.linux.org.uk>
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On Fri, Feb 13, 2015 at 08:54:22PM +0000, Magnus Damm wrote:
> Thanks for your efforts. Can you please tell me where that limitation
> is located? I'm quite sure I've brought CPU cores up and down
> including CPU0, but maybe something is missing?

If you don't provide a cpu_disable function, by default only the non-boot
(iow, non-CPU0) CPUs can be hotplugged.

If you provide a cpu_disable function, it can instruct the system that
fewer or more CPUs can be hotplugged, including the boot CPU.  The system
will then restrict you to a minimum of any one CPU online.

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