# Re: \[RFC PATCH v1 08/16\] unwind\_user: Enable archs that save RA/FP in other registers

- From: Steven Rostedt \<rostedt@goodmis.org\>
- Date: 2025-07-17 12:10:08 
- List: linux-trace-kernel
- Page: https://ratatoskr.run/linux-trace-kernel/2025/07/3138548
- Thread: https://ratatoskr.run/linux-trace-kernel/2025/07/3129870/t.md

```text
On Thu, 17 Jul 2025 13:28:25 +0200
Jens Remus [ref] wrote:

> >> +	default:
> >> +		WARN_ON_ONCE(1);
> >> +		goto done;  
> > 
> > The default case will never happen, can we make it a BUG()?  
> 
> Whatever Steve and you agree on.  I am new to Kernel development.

Keep the WARN_ON(). Linus has yelled at people for using BUG() when a
WARN_ON() would do.

WARN_ON() is meant for things that should never happen. BUG() is reserved
for places in the kernel that is dangerous to continue.

It's even documented:

  https://docs.kernel.org/process/deprecated.html#bug-and-bug-on

-- Steve
```