linux-kernel - Re: [Suggestion] about calling debug_hotplug_cpu() which enabled by 'allmodconfig' for a x86

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Message-ID: <1380727725.5429.13.camel@misato.fc.hp.com>
Date:	Wed, 02 Oct 2013 09:28:45 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Chen Gang <gang.chen@...anux.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	"Yu, Fenghua" <fenghua.yu@...el.com>,
	"rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
	"isimatu.yasuaki@...fujitsu.com" <isimatu.yasuaki@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Suggestion] about calling debug_hotplug_cpu() which enabled by
 'allmodconfig' for a x86_64 dual core laptop.

On Wed, 2013-10-02 at 03:10 +0000, Chen Gang wrote:
> Hello Maintainers:
> 
> Under my x86_64 dual core laptop, I build kernel next-20130927 with
> 'allmodconfig', and install it, the machine can not start. Related
> information is:
> 
>   after call debug_hotplug_cpu(), output "cpu 0 is offline" .... and then "Failed to execute /init".
> 
> After remove "_debug_hotplug_cpu(0, 0);", can pass the issue (but will
> fail in another place). I guess, the reason is my laptop cpu is not
> 'hotplug', but have to call debug_hotplug_cpu() with allmodconfig.
> 
> 
> I will continue analyzing, welcome any additional suggestions or
> completions.

allmodconfig sets CONFIG_DEBUG_HOTPLUG_CPU0 to y (which is defined as
"def_bool n"), which puts CPU0 offline during boot for testing.  This
debug feature is causing the problem on your laptop.  I am not familiar
with allmodconfig, but it seems that it enables all the config options,
preferably with 'm'.

Thanks,
-Toshi

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