Messages in this thread | | | Subject | Re: [Suggestion] about calling debug_hotplug_cpu() which enabled by 'allmodconfig' for a x86_64 dual core laptop. | From | Toshi Kani <> | Date | Wed, 02 Oct 2013 13:33:11 -0600 |
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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.
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