From: Sebastian Andrzej Siewior Date: Mon, 11 Apr 2016 16:55:02 +0200 Subject: [PATCH] tty: serial: 8250: don't take the trylock during oops Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.25-rt16.tar.xz An oops with irqs off (panic() from irqsafe hrtimer like the watchdog timer) will lead to a lockdep warning on each invocation and as such never completes. Therefore we skip the trylock in the oops case. Signed-off-by: Sebastian Andrzej Siewior --- drivers/tty/serial/8250/8250_port.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -3239,10 +3239,8 @@ void serial8250_console_write(struct uar serial8250_rpm_get(up); - if (port->sysrq) + if (port->sysrq || oops_in_progress) locked = 0; - else if (oops_in_progress) - locked = spin_trylock_irqsave(&port->lock, flags); else spin_lock_irqsave(&port->lock, flags);