From: Sebastian Andrzej Siewior Date: Mon, 11 Apr 2016 16:55:02 +0200 Subject: [PATCH 168/353] tty: serial: 8250: don't take the trylock during oops Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=fedac9e5838862f2a77d0d8a34b4b0bffca76c83 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(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index cba4888bc482..af7df5ca17a5 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -3316,10 +3316,8 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, 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);