Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754275Ab3JBTgn (ORCPT ); Wed, 2 Oct 2013 15:36:43 -0400 Received: from g4t0015.houston.hp.com ([15.201.24.18]:26685 "EHLO g4t0015.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753610Ab3JBTgl (ORCPT ); Wed, 2 Oct 2013 15:36:41 -0400 Message-ID: <1380742391.5429.37.camel@misato.fc.hp.com> Subject: Re: [Suggestion] about calling debug_hotplug_cpu() which enabled by 'allmodconfig' for a x86_64 dual core laptop. From: Toshi Kani To: Chen Gang F T Cc: Chen Gang , 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" Date: Wed, 02 Oct 2013 13:33:11 -0600 In-Reply-To: <524C4CC9.3080402@gmail.com> References: <524B8E97.1030707@asianux.com> <1380727725.5429.13.camel@misato.fc.hp.com> <524C4CC9.3080402@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.8.5 (3.8.5-2.fc19) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2365 Lines: 56 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. -- 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/