nbcon/reboot: Switch NBCON consoles into the emergency mode in emergency_restart()

When the system is going down a normal way, the NBCON kthreads are
flushed and stopped properly via a syscore shutdown callback, see
printk_kthreads_shutdown().

One missing piece is emergency_restart() where the kthreads are not
stopped. It might be called from several non-panic code paths,
e.g. sysrq-o, kdb_reboot(), or some watchdogs.

Fix it by explicitly entering the emergency (atomic) mode and trying
to flush the consoles there.

Note that printk_trigger_flush() must be used instead of pr_flush()
because the later is not safe in an atomic context.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/all/202608061008.48a1e76e-lkp@intel.com/
Suggested-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Link: https://patch.msgid.link/20261013154141.94016-1-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>

0 files changed, 0 insertions, 0 deletions