# Re: \[PATCH 2/3\] powerpc/cpuhp: BUG -\> WARN conversion in offline path

- From: Christophe Leroy \<hidden\>
- Date: 2021-09-20 14:27:05 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2021/09/9524448
- Thread: https://ratatoskr.run/linuxppc-dev/2021/09/9524444/t.md

```text


Le 20/09/2021 à 15:55, Nathan Lynch a écrit :
> If, due to bugs elsewhere, we get into unregister_cpu_online() with a CPU
> that isn't marked hotpluggable, we can emit a warning and return an
> appropriate error instead of crashing.

Is it only a bug situation, or is it something that can happen in real life ?

If it can happen in real life, kernels with panic_on_warn will still be impacted.

>
> Signed-off-by: Nathan Lynch <redacted>
> ---
>   arch/powerpc/kernel/sysfs.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
> index defecb3b1b15..08d8072d6e7a 100644
> --- a/arch/powerpc/kernel/sysfs.c
> +++ b/arch/powerpc/kernel/sysfs.c
> @@ -928,7 +928,8 @@ static int unregister_cpu_online(unsigned int cpu)
>   	struct device_attribute *attrs, *pmc_attrs;
>   	int i, nattrs;
>   
> -	BUG_ON(!c->hotpluggable);
> +	if (WARN_RATELIMIT(!c->hotpluggable, "cpu %d can't be offlined\n", cpu))
> +		return -EBUSY;
>   
>   #ifdef CONFIG_PPC64
>   	if (cpu_has_feature(CPU_FTR_SMT))
>
```