On Thu, 2013-10-03 at 00:49 +0000, Chen Gang wrote: > 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". :-)
Good. :) > >> 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. I see. If this option is used for testing, enabling DEBUG_HOTPLUG_CPU0 does make sense. Thanks, -Toshi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
