Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753933Ab3JCAue (ORCPT ); Wed, 2 Oct 2013 20:50:34 -0400 Received: from intranet.asianux.com ([58.214.24.6]:38702 "EHLO intranet.asianux.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753326Ab3JCAud (ORCPT ); Wed, 2 Oct 2013 20:50:33 -0400 X-Spam-Score: -100.9 Message-ID: <524CBF19.2030708@asianux.com> Date: Thu, 03 Oct 2013 08:49:29 +0800 From: Chen Gang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: Toshi Kani CC: Thomas Gleixner , "mingo@redhat.com" , "H. Peter Anvin" , the arch/x86 maintainers , "Yu, Fenghua" , "rafael.j.wysocki@intel.com" , "isimatu.yasuaki@jp.fujitsu.com" , "linux-kernel@vger.kernel.org" Subject: Re: [Suggestion] about calling debug_hotplug_cpu() which enabled by 'allmodconfig' for a x86_64 dual core laptop. References: <524B8E97.1030707@asianux.com> <1380727725.5429.13.camel@misato.fc.hp.com> <524C4CC9.3080402@gmail.com> <1380742391.5429.37.camel@misato.fc.hp.com> In-Reply-To: <1380742391.5429.37.camel@misato.fc.hp.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2879 Lines: 77 On 10/03/2013 03:33 AM, Toshi Kani wrote: > 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. > Thank you for your confirmation, "for dual core (although laptop), after system boot up, can let cpu0 offline". :-) >> 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. > Hmm... I will continue analyzing. After finish analyzing (let kernel boot up OK), I should give a confirmation: "during boot up, can we still let cpu0 offline for dual core?". In fact, 'allmodconfig' is just a mad user which often does useless things to intend to find issues. Thanks. > 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. > > > > > -- Chen Gang -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/