[BUG] Threaded printk breaks early debugging

[John Ogness]

Hi Peter,

On 2022-06-10, Peter Geis <pgwipeout at gmail.com> wrote:
> However I've run into an issue debugging early boot issues. Anything
> that causes the kernel threading system to die (for example here, a
> NPE) causes the boot console to halt before it outputs the error.

A null pointer exception should trigger a panic, which will cause printk
to enter direct mode for the oops. It should be just as effective as
before introducing the printing kthreads.

Can you please provide a test case or patch that will trigger the
problem you refer to?

> Would it be possible to have both a kconfig option and a runtime
> option to toggle printk_fallback_preferred_direct()? Currently I've
> had to force it at all times while debugging.

It would be trivial to provide a boot parameter for this behavior, but I
think we first need to see a real problem and also see if we can fix
that problem.

John Ogness