Re: [linux-next:master] [serial] d353934702: BUG:kernel_reboot-without-warning_in_test_stage

[John Ogness <john.ogness@linutronix.de>]

Hi Petr,

On 2026-09-23, John Ogness <john.ogness@linutronix.de> wrote:
>> diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
>> index d17704fe93ae..48446926dc50 100644
>> --- a/kernel/printk/nbcon.c
>> +++ b/kernel/printk/nbcon.c
>> @@ -1446,6 +1446,10 @@ enum nbcon_prio nbcon_get_default_prio(void)
>>  	if (panic_on_this_cpu())
>>  		return NBCON_PRIO_PANIC;
>>  
>> +	/* Do not rely on kthreads when the system is going down. */
>> +	if (system_state > SYSTEM_RUNNING)
>> +		return NBCON_PRIO_EMERGENCY;
>> +
>>  	cpu_emergency_nesting = nbcon_get_cpu_emergency_nesting();
>>  	if (*cpu_emergency_nesting)
>>  		return NBCON_PRIO_EMERGENCY;
>> diff --git a/kernel/reboot.c b/kernel/reboot.c
>> index d177d89fcc33..776784a82499 100644
>> --- a/kernel/reboot.c
>> +++ b/kernel/reboot.c
>> @@ -8,6 +8,7 @@
>>  #define pr_fmt(fmt)	"reboot: " fmt
>>  
>>  #include <linux/atomic.h>
>> +#include <linux/console.h>
>>  #include <linux/ctype.h>
>>  #include <linux/export.h>
>>  #include <linux/kexec.h>
>> @@ -94,6 +95,7 @@ void emergency_restart(void)
>>  {
>>  	kmsg_dump(KMSG_DUMP_EMERG);
>>  	system_state = SYSTEM_RESTART;
>> +	printk_trigger_flush();
>>  	machine_emergency_restart();
>>  }
>>  EXPORT_SYMBOL_GPL(emergency_restart);
>> @@ -102,6 +104,7 @@ void kernel_restart_prepare(char *cmd)
>>  {
>>  	blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
>>  	system_state = SYSTEM_RESTART;
>> +	printk_trigger_flush();
>>  	usermodehelper_disable();
>>  	device_shutdown();
>>  }
>> @@ -305,6 +308,7 @@ static void kernel_shutdown_prepare(enum system_states state)
>>  	blocking_notifier_call_chain(&reboot_notifier_list,
>>  		(state == SYSTEM_HALT) ? SYS_HALT : SYS_POWER_OFF, NULL);
>>  	system_state = state;
>> +	printk_trigger_flush();
>>  	usermodehelper_disable();
>>  	device_shutdown();
>>  }
>
> I am OK with this change.

If you want to roll this into an official patch:

Reviewed-by: John Ogness <john.ogness@linutronix.de>