Re: [PATCH V2] MIPS: Fix poweroff failure when HOTPLUG_CPU configured.

[Kevin Cernekee <cernekee@gmail.com>]

On Mon, Aug 13, 2012 at 5:52 AM, Huacai Chen <chenhc@lemote.com> wrote:
> When poweroff machine, kernel_power_off() call disable_nonboot_cpus().
> And if we have HOTPLUG_CPU configured, disable_nonboot_cpus() is not an
> empty function but attempt to actually disable the nonboot cpus. Since
> system state is SYSTEM_POWER_OFF, play_dead() won't be called and thus
> disable_nonboot_cpus() hangs. Therefore, we make this patch to avoid
> poweroff failure.

I have seen the same problem; sometimes it causes a kernel oops too.

>  #ifdef CONFIG_HOTPLUG_CPU
> -               if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map) &&
> -                   (system_state == SYSTEM_RUNNING ||
> -                    system_state == SYSTEM_BOOTING))
> +               if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map))
>                         play_dead();

This fix works for me.

Acked-by: Kevin Cernekee <cernekee@gmail.com>

I do see SMP boot problems ("Attempted to kill the idle task!" panic)
on a 4-way box if the !cpu_isset() check is removed.