Messages in this thread | | | Date | Tue, 15 Aug 2023 12:10:17 +0200 | Subject | Re: [PATCH] serial: 8250: drop lockdep annotation from serial8250_clear_IER() | From | Jiri Slaby <> |
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On 15. 08. 23, 11:27, Petr Mladek wrote: > On Mon 2023-08-14 12:21:23, Jiri Slaby wrote: >> On 14. 08. 23, 12:00, Petr Mladek wrote: >>> I personally vote to keep it as is unless people see this warning >>> on daily basis. After all, the lockdep splat is correct. The serial >>> console might not work correctly in panic() when there is the race. >> >> Sorry, but no, the warning is not correct at all. The code path deliberately >> does NOT take the lock and calls a function which is currently annotated >> that the lock is _always_ taken. Therefore, the warning is clearly a false >> positive and I see no reason in keeping it. > > There might be a misunderstanding. I only want to keep panic() > implementation as it is for now. I mean to keep calling > debug_locks_off() right before console_flush_on_panic(). > The lockdep should stay on before to report potential problems > in non-printk code, like kexec, panic notifiers. > > But I am fine with disabling the particular lockdep_assert_held_once() > during panic(). > > It should stay during the normal system state to catch not > yet discovered races. John is working hard on preventing any > races which might blow up after introducing the printk kthreads. > > I mean something like: > > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c > index ecfdc4534123..9533c1eedfb1 100644 > --- a/drivers/tty/serial/8250/8250_port.c > +++ b/drivers/tty/serial/8250/8250_port.c > @@ -704,7 +704,8 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) > static void serial8250_clear_IER(struct uart_8250_port *up) > { > /* Port locked to synchronize UART_IER access against the console. */ > - lockdep_assert_held_once(&up->port.lock); > + if (!oops_in_progress) > + lockdep_assert_held_once(&up->port.lock);
Yes, this is one of my suggestions ;). (Which I thought are not worth it, but I am not opposing either.)
thanks, -- js suse labs
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