From 42b6a1baa3ec18de2eb15baa250da6203eeb2d39 Mon Sep 17 00:00:00 2001 From: Randy Witt Date: Thu, 17 Oct 2013 16:56:47 -0400 Subject: serial_core: Don't re-initialize a previously initialized spinlock. The uart_set_options() code unconditionally initalizes the spinlock on the port. This can cause a deadlock in some situations. One instance that exposed the problem, was when writing to /sys/module/kgdboc/parameters/kgdboc to use ttyS0 when the console is already running on ttyS0. If the spinlock is re-initialized while the lock is held due to output to the console, there is a deadlock. Assume the spinlock is initialized if the port is a console. Signed-off-by: Randy Witt Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/serial_core.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'drivers/tty/serial/serial_core.c') diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 0f02351..ece2049 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1830,9 +1830,13 @@ uart_set_options(struct uart_port *port, struct console *co, /* * Ensure that the serial console lock is initialised * early. + * If this port is a console, then the spinlock is already + * initialised. */ - spin_lock_init(&port->lock); - lockdep_set_class(&port->lock, &port_lock_key); + if (!(uart_console(port) && (port->cons->flags & CON_ENABLED))) { + spin_lock_init(&port->lock); + lockdep_set_class(&port->lock, &port_lock_key); + } memset(&termios, 0, sizeof(struct ktermios)); -- cgit v1.1