On 2018-05-03 09:43:33 [+0200], Geert Uytterhoeven wrote:
> > --- a/drivers/tty/serial/sh-sci.c
> > +++ b/drivers/tty/serial/sh-sci.c
> > @@ -2516,13 +2516,12 @@ static void serial_console_write(struct console *co, const char *s,
> > unsigned long flags;
> > int locked = 1;
> >
> > - local_irq_save(flags);
>
> Hence the below now runs with local interrupts enabled.
>
> For checking port->sysrq or oops_in_progress that probably isn't an issue.
> If oops_in_progress is set, you have other problems, and the race condition
> between checking the flag and calling spin_lock{,_irqsave}() existed before,
> and is hard to avoid.
while oops_in_progress is an issue of its own, the port->sysrq isn't
avoided by by local_irq_save(). On SMP systems you can still receive a
`break' signal on the UART and have a `printk()' issued on another CPU.
> For actual console printing, I think you want to keep interrupts disabled.
why? They should be disabled as part of getting the lock and not for any
other reason.
> > if (port->sysrq)
> > locked = 0;
> > else if (oops_in_progress)
> > - locked = spin_trylock(&port->lock);
> > + locked = spin_trylock_irqsave(&port->lock, flags);
> > else
> > - spin_lock(&port->lock);
> > + spin_lock_irqsave(&port->lock, flags);
>
> Add
>
> if (!locked
> local_irq_save(flags)
>
> here?
So for oops_in_progress you get here with interrupts disabled. And if
not, I don't see the point in disabling the interrupts without any kind
of locking.
> Gr{oetje,eeting}s,
>
> Geert
>
Sebastian
--
To unsubscribe from this list: send the line "unsubscribe linux-serial" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
