linux-kernel - Re: [PATCHv2] arm: platsmp: Allow secondary cpu hotplug with maxcpus=1

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Date:	Wed, 6 Jul 2011 23:55:50 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-sh@...r.kernel.org, linux-tegra@...r.kernel.org,
	Paul Mundt <lethal@...ux-sh.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	David Brown <davidb@...eaurora.org>,
	Tony Lindgren <tony@...mide.com>,
	Srinidhi Kasagar <srinidhi.kasagar@...ricsson.com>,
	Linus Walleij <linus.walleij@...ricsson.com>
Subject: Re: [PATCHv2] arm: platsmp: Allow secondary cpu hotplug with
	maxcpus=1

On Tue, Jul 05, 2011 at 10:29:17AM -0700, Stephen Boyd wrote:
> If an ARM system has multiple cpus in the same socket and the
> kernel is booted with maxcpus=1, secondary cpus are possible but
> not present due to how platform_smp_prepare_cpus() is called.
> Since most typical ARM processors don't actually support physical
> hotplug, initialize the present map to be equal to the possible
> map in generic ARM SMP code. Also, always call
> platform_smp_prepare_cpus() as long as max_cpus is non-zero (0
> means no SMP) to allow platform code to do any SMP setup.
> 
> After applying this patch it's possible to boot an ARM system
> with maxcpus=1 on the command line and then hotplug in secondary
> cpus via sysfs. This is more in line with how x86 does things.

Ok - how about putting this in the patch system?

Thanks.
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