Re: [PATCH] nbcon/reboot: Flush nbcon consoles synchronously on reboot

[Petr Mladek <pmladek@suse.com>]

On Fri 2026-10-09 15:34:30, John Ogness wrote:
> On 2026-10-09, Petr Mladek <pmladek@suse.com> wrote:
> > Anyway, IMHO, we should switch to NBCON_PRIO_EMERGENCY for the post-running
> > states and flush the pending messages immediately. It is more
> > reliable. It is easy to find the locations when system_state() is set.
> > And all follow-up printk() calls will try the direct flush so that
> > they won't rely on an explicit flush.
> 
> We need to be careful about abusing CPU state in order to get certain
> functionality. We already have things in place to gracefully switch to
> atomic after shutting down the printing kthreads.

This explains why I see the messages even without this patch.
I wonder what is actually going on in the test.

The log contains:

</paste>
LKP: ttyS0: 256: LKP: tbox cant kexec and rebooting forcely
</paste>

I see this message in lkp-tests/bin/lkp-setup-rootfs:

<cat lkp-tests/bin/lkp-setup-rootfs>
lkp_reboot()
{
	local tbox_state="rebooting"
	[ -n "$1" ] && tbox_state="rebooting_$1"

	set_tbox_wtmp $tbox_state

	# Avoid get stuck in yocto minimal rootfs.
	# LKP: rebooting
	# [    8.124081] LKP: rebooting
	# # (shell prompt)
	is_virt && [ -e '/proc/sysrq-trigger' ] && {
		sync
		echo s >/proc/sysrq-trigger
		echo b >/proc/sysrq-trigger
	}

	start_reboot_watchdog
	reboot_tbox 2>/dev/null

	exit
}
[...]
	if tbox_cant_kexec; then
		echo_to_tty "LKP: tbox cant kexec and rebooting forcely"
		lkp_reboot "cant_kexec"
	fi
</cat lkp-tests/bin/lkp-setup-rootfs>

so, it ends with reboot_tbox which is:

<cat lkp-tests/lib/reboot.sh>
reboot_tbox()
{
	reboot
}
</cat lkp-tests/lib/reboot.sh

which is classic reboot. I am not sure where it expects the warning.
I actually can't find the code which prints:

<paste>
BUG: kernel reboot-without-warning in test stage
</paste>

I might need to try reproducing it with the lkp-test framework.
But it has to wait for the next week.

Best Regards,
Petr