Re: [PATCH V2] MIPS: CPU#0 is not hotpluggable

[Huacai Chen <chenhuacai@gmail.com>]

Hi, Thomas,

What do you think about this patch? Other archs also do the same thing
except those support hotplug CPU#0.

grep hotpluggable arch -rwI
arch/riscv/kernel/setup.c:        cpu->hotpluggable = cpu_has_hotplug(i);
arch/powerpc/kernel/sysfs.c:    BUG_ON(!c->hotpluggable);
arch/powerpc/kernel/sysfs.c:            c->hotpluggable = 1;
arch/powerpc/kernel/sysfs.c:        if (cpu_online(cpu) || c->hotpluggable) {
arch/arm/kernel/setup.c:        cpuinfo->cpu.hotpluggable =
platform_can_hotplug_cpu(cpu);
arch/sh/kernel/topology.c:        c->hotpluggable = 1;
arch/ia64/kernel/topology.c:     * CPEI target, then it is hotpluggable
arch/ia64/kernel/topology.c:        sysfs_cpus[num].cpu.hotpluggable = 1;
arch/xtensa/kernel/setup.c:        cpu->hotpluggable = !!i;
arch/s390/kernel/smp.c:    c->hotpluggable = 1;
arch/mips/kernel/topology.c:        c->hotpluggable = 1;
arch/arm64/kernel/cpuinfo.c: * In case the boot CPU is hotpluggable,
we record its initial state and
arch/arm64/kernel/setup.c:        cpu->hotpluggable = cpu_can_disable(i);
arch/x86/kernel/topology.c:        per_cpu(cpu_devices,
num).cpu.hotpluggable = 1;

On Thu, Jul 16, 2020 at 6:38 PM Huacai Chen <chenhc@lemote.com> wrote:
>
> Now CPU#0 is not hotpluggable on MIPS, so prevent to create /sys/devices
> /system/cpu/cpu0/online which confuses some user-space tools.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Huacai Chen <chenhc@lemote.com>
> ---
>  arch/mips/kernel/topology.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/mips/kernel/topology.c b/arch/mips/kernel/topology.c
> index cd3e1f8..08ad637 100644
> --- a/arch/mips/kernel/topology.c
> +++ b/arch/mips/kernel/topology.c
> @@ -20,7 +20,7 @@ static int __init topology_init(void)
>         for_each_present_cpu(i) {
>                 struct cpu *c = &per_cpu(cpu_devices, i);
>
> -               c->hotpluggable = 1;
> +               c->hotpluggable = !!i;
>                 ret = register_cpu(c, i);
>                 if (ret)
>                         printk(KERN_WARNING "topology_init: register_cpu %d "
> --
> 2.7.0
>