On 2023-09-15, Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx> wrote:
>> @@ -3403,9 +3403,9 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
>> touch_nmi_watchdog();
>>
>> if (oops_in_progress)
>> - locked = spin_trylock_irqsave(&port->lock, flags);
>> + locked = uart_port_trylock_irqsave(port, &flags);
>> else
>> - spin_lock_irqsave(&port->lock, flags);
>> + uart_port_lock_irqsave(port, &flags);
>
> Not related to any problem (with this patch) but I'm a bit curious is
> this construct going to remain there after the follow-up work?
Yes. The uart port lock already provides excellent coverage of unsafe
regions in uart drivers. We want to take advantage of that.
> And there's the similar one in some other drivers (with some
> variations related to local_irq_save()):
>
> if (port->sysrq) {
> locked = 0;
> } else if (oops_in_progress) {
> locked = spin_trylock(&port->lock);
> } else {
> spin_lock(&port->lock);
> locked = 1;
> }
With the follow-up work we are introducing a new type of console
(CON_NBCON) that supports atomic and threaded printing. Current console
drivers must be converted if they want these features. When converting a
driver to NBCON, such variations as above will need to be addressed. The
follow-up work provides new functions and semantics to allow drivers to
implement more reliable code than just: "trylock and keep going no
matter what".
For console drivers that are _not_ converted to NBCON, the uart port
lock wrappers will not provide any changed functionality.
John Ogness
