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

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Date:	Thu, 03 Oct 2013 09:07:23 -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 Thu, 2013-10-03 at 22:21 +0800, Chen Gang wrote:
> One root cause found (but not only one), allmodconfig will enable
> CONFIG_SYSFS_DEPRECATED which for new kernel on old distribution.
> 
> 
> I am comparing from allmodconfig config file to defconfig config file,
> the attachments are middle files (one enable CONFIG_SYSFS_DEPRECATED
> which can not boot up, the other disable it which can boot up).
> 
> The related information in "init/Kconfig"
> 
>   config SYSFS_DEPRECATED
>     bool "Enable deprecated sysfs features to support old userspace tools"
>     depends on SYSFS
>     default n
>     help
>       This option adds code that switches the layout of the "block" class
>       devices, to not show up in /sys/class/block/, but only in
>       /sys/block/.
> 
>       This switch is only active when the sysfs.deprecated=1 boot option is
>       passed or the SYSFS_DEPRECATED_V2 option is set.
> 
>       This option allows new kernels to run on old distributions and tools,
>       which might get confused by /sys/class/block/. Since 2007/2008 all
>       major distributions and tools handle this just fine.
> 
>       Recent distributions and userspace tools after 2009/2010 depend on
>       the existence of /sys/class/block/, and will not work with this
>       option enabled.
> 
>       Only if you are using a new kernel on an old distribution, you might
>       need to say Y here.
> 
> 
> I will continue to analyze another related issues for allmodconfig on
> my laptop (after disable SYSFS_DEPRECATED, for allmodconfig, it still
> can not boot up successfully, although my 'middle' config file can).

Since this is no longer a hotplug issue, I'd suggest you change the
subject line and resend it to the folks who worked on this config
option.  I won't be able to help on this one.

-Toshi


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