Re: [PATCH RFC printk] printk: Postpone kthread startup

[John Ogness]

On 2026-10-15, John Ogness <john.ogness@xxxxxxxxxxxxx> wrote:
> There have been various bug reports related to SMP systems hanging
> on boot. The reports vary wildly but seem to have some overlap with
> regard to missed IPI's during SMP setup. The reports also show that
> reverting NBCON console usage allows the bugs to disappear.
>
> The NBCON kthreads for console printing are started very early
> during boot using early_initcall(). Since these kthreads are
> actively enabling/disabling interrupts during early boot, they may
> be interfering with SMP setup.
>
> Postpone kthread starting until after all arch initcalls have
> completed.

This should also contain:

Reported-by: Derek Barbosa <debarbos@xxxxxxxxxx>
Closes: https://lore.kernel.org/linux-rt-users/arPmYPbFLf2EldIl@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 5f1b414ca027 ("printk: nbcon: Start printing threads")