# \[PATCH v2 2/4\] powerpc/cpuhp: BUG -\> WARN conversion in offline path

- From: Nathan Lynch \<hidden\>
- Date: 2021-09-27 20:23:13 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2021/09/9524525
- Thread: https://ratatoskr.run/linuxppc-dev/2021/09/9524522/t.md

```text
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.

Signed-off-by: Nathan Lynch <redacted>
Reviewed-by: Daniel Henrique Barboza <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))
-- 
2.31.1

```