Re: [PATCH v3 3/4] printk: nbcon: Allow KDB to acquire the NBCON context

[John Ogness]

On 2025-09-08, Petr Mladek <pmladek@xxxxxxxx> wrote:
> On Fri 2025-09-05 16:58:34, John Ogness wrote:
>> On 2025-09-02, Marcos Paulo de Souza <mpdesouza@xxxxxxxx> wrote:
>> > diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
>> > index ff218e95a505fd10521c2c4dfb00ad5ec5773953..352235a0eb4a484caccf86d3a57d1a149218ecec 100644
>> > --- a/kernel/printk/nbcon.c
>> > +++ b/kernel/printk/nbcon.c
>> > @@ -255,6 +258,7 @@ static int nbcon_context_try_acquire_direct(struct nbcon_context *ctxt,
>> >  		 * interrupted by the panic CPU while printing.
>> >  		 */
>> >  		if (other_cpu_in_panic() &&
>> > +		    READ_ONCE(kdb_printf_cpu) != raw_smp_processor_id() &&
>> 
>> This needs some sort of ifdef CONFIG_KGDB_KDB wrapped around it. Maybe
>> it would be cleaner to have some macro.
>
> Great catch!
>
>> #ifdef CONFIG_KGDB_KDB
>> #define KGDB_IS_ACTIVE() (READ_ONCE(kdb_printf_cpu) == raw_smp_processor_id())
>> #else
>> #define KGDB_IS_ACTIVE() false
>> #endif
>
> I like this. It would fit into include/linux/kdb.h which already
> contains the #ifdef CONFIG_KGDB_KDB / #else / #endif sections.

BTW, if there is such a macro created, it should be KDB_IS_ACTIVE()
rather than KGDB_IS_ACTIVE().

John