Thomas Gleixner <t...@linutronix.de> writes:
> On Wed, 26 Jul 2017, Michael Ellerman wrote:
>
>> Hi Thomas,
>>
>> I'm seeing the lockdep barf below on some bare metal Power8 machines.
>>
>> This seems to be caused by our smp_cpus_done(), which does:
>>
>> void __init smp_cpus_done(unsigned int max_cpus)
>> {
>> /*
>> * We want the setup_cpu() here to be called on the boot CPU, but
>> * init might run on any CPU, so make sure it's invoked on the boot
>> * CPU.
>> */
>> if (smp_ops && smp_ops->setup_cpu)
>> work_on_cpu_safe(boot_cpuid, smp_setup_cpu_workfn, NULL);
>>
>>
>> I don't think CPU hotplug can happen at this point, so I don't think
>> there's really a bug.
>>
>> But it looks like the work_on_cpu_safe() call could just go away, since
>> you pinned init to the boot CPU in 8fb12156b8db ("init: Pin init task to
>> the boot CPU, initially"). Though I can't see where init is unpinned, so
>> maybe we do still need to do it?
>
> It's undone in sched_init_smp(). So it looks safe. The call order is:
>
> smp_init()
> ...
> smp_cpus_done()
>
> sched_init_smp()
Great thanks.
Patch on the way.
cheers
