Messages in this thread | | | Date | Thu, 03 Oct 2013 08:49:29 +0800 | From | Chen Gang <> | Subject | Re: [Suggestion] about calling debug_hotplug_cpu() which enabled by 'allmodconfig' for a x86_64 dual core laptop. |
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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
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