From: Toshi Kani <toshi.kani@hp.com>
To: Chen Gang F T <chen.gang.flying.transformer@gmail.com>
Cc: Chen Gang <gang.chen@asianux.com>,
Thomas Gleixner <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>,
the arch/x86 maintainers <x86@kernel.org>,
"Yu, Fenghua" <fenghua.yu@intel.com>,
"rafael.j.wysocki@intel.com" <rafael.j.wysocki@intel.com>,
"isimatu.yasuaki@jp.fujitsu.com" <isimatu.yasuaki@jp.fujitsu.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [Suggestion] about calling debug_hotplug_cpu() which enabled by 'allmodconfig' for a x86_64 dual core laptop.
Date: Wed, 02 Oct 2013 13:33:11 -0600 [thread overview]
Message-ID: <1380742391.5429.37.camel@misato.fc.hp.com> (raw)
In-Reply-To: <524C4CC9.3080402@gmail.com>
On Thu, 2013-10-03 at 00:41 +0800, Chen Gang F T wrote:
> On 10/02/2013 11:28 PM, Toshi Kani wrote:
> > 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'.
> >
>
> Hmm... excuse me, I don't know: for laptop, if cpu0 is offline, whether
> it still can work or not. If any members know about it, please tell me,
> thanks.
CPU online/offline works on laptops as long as they have more than one
CPU. You can boot with other kernel and test this feature
with /sys/devices/system/cpu/cpuX/online on your laptop. cpu0 is a
special case and you may need to specify "cpu0_hotplug" boot option.
> In my opinion, if enable DEBUG_HOTPLUG_CPU0, but "should not let cpu0
> offline for laptop", we need let 'offline' operation fail.
Whether it is a laptop or not should not be a matter here. But I agree
with you that enabling CONFIG_DEBUG_HOTPLUG_CPU0 is not useful (and can
be harmful) unless a user really intends to test this feature.
Thanks,
-Toshi
> And I am analyzing (just constructing environments: KVM, kgdb ...),
> before let kernel start successfully, only according to my current
> proofs, we can not say "let laptop cpu0 offline" must be an issue.
next prev parent reply other threads:[~2013-10-02 19:36 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-02 3:10 [Suggestion] about calling debug_hotplug_cpu() which enabled by 'allmodconfig' for a x86_64 dual core laptop Chen Gang
2013-10-02 15:28 ` Toshi Kani
2013-10-02 16:41 ` Chen Gang F T
2013-10-02 19:33 ` Toshi Kani [this message]
2013-10-03 0:49 ` Chen Gang
2013-10-03 14:21 ` Chen Gang
2013-10-03 15:07 ` Toshi Kani
2013-10-04 9:27 ` Chen Gang
2013-10-03 14:51 ` Toshi Kani
2013-10-04 10:54 ` Chen Gang F T
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