# 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 03:57:39 
- List: linux-trace-kernel
- Page: https://ratatoskr.run/linux-trace-kernel/2025/07/3137949
- Thread: https://ratatoskr.run/linux-trace-kernel/2025/07/3129870/t.md

```text
On Wed, 16 Jul 2025 19:01:06 -0700
Josh Poimboeuf [ref] wrote:

> > +		if (unwind_user_get_reg(&ra, frame->ra.regnum))
> > +			goto done;
> > +		break;
> > +	default:
> > +		WARN_ON_ONCE(1);
> > +		goto done;  
> 
> The default case will never happen, can we make it a BUG()?

Is this really serious enough to crash the system? WARN_ON_ONCE() *is* for
things that will never happen.

The only time I ever use BUG() is if it's too dangerous to continue (like a
function graph trampoline that gets corrupted and has no place to return
to). In general, usage of BUG() should be avoided.

-- Steve
```