From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Andrzej Siewior Subject: [RFC RT] tty: serial: 8250: don't take the lock on OOPs Date: Fri, 11 Mar 2016 19:05:04 +0100 Message-ID: <20160311180504.GB29850@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org To: tglx@linutronix.de, rostedt@goodmis.org Return-path: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org On panic() from IRQ (for instance from the lockup detector) we will end up in an endless loop on -RT. Each time we invoke spin_trylock_irqsave() we will trigger the WARN_ON() in rt_mutex_trylock(). The WARN_ON() will stuff more data into the printk buffer than we can print on one iteration and so we never end the printing loop. Signed-off-by: Sebastian Andrzej Siewior --- drivers/tty/serial/8250/8250_port.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 5568d70eee0c..138b1b985063 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2850,9 +2850,9 @@ 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 || in_kdb_printk()) + else if (in_kdb_printk()) locked = spin_trylock_irqsave(&port->lock, flags); else spin_lock_irqsave(&port->lock, flags); -- 2.7.0