From: Randy Witt Date: Thu, 17 Oct 2013 20:56:47 +0000 (-0400) Subject: serial_core: Don't re-initialize a previously initialized spinlock. X-Git-Tag: firefly_0821_release~176^2~4543^2~62 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=42b6a1baa3ec18de2eb15baa250da6203eeb2d39;p=firefly-linux-kernel-4.4.55.git 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 --- diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 0f02351c9239..ece2049bd270 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));