[PATCH] Serial: Adjust serial locking

This patch changes the way serial ports are locked when getting modem
status.  This change is necessary because we will need to atomically
read the modem status and take action depending on the CTS status.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 36b1ae083fb..f5ce58d0514 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -828,7 +828,10 @@ static int uart_tiocmget(struct tty_struct *tty, struct file *file)
         if ((!file || !tty_hung_up_p(file)) &&
             !(tty->flags & (1 << TTY_IO_ERROR))) {
                 result = port->mctrl;
+
+                spin_lock_irq(&port->lock);
                 result |= port->ops->get_mctrl(port);
+                spin_unlock_irq(&port->lock);
         }
         up(&state->sem);
 
@@ -1369,6 +1372,7 @@ uart_block_til_ready(struct file *filp, struct uart_state *state)
         DECLARE_WAITQUEUE(wait, current);
         struct uart_info *info = state->info;
         struct uart_port *port = state->port;
+        unsigned int mctrl;
 
         info->blocked_open++;
         state->count--;
@@ -1416,7 +1420,10 @@ uart_block_til_ready(struct file *filp, struct uart_state *state)
                  * and wait for the carrier to indicate that the
                  * modem is ready for us.
                  */
-                if (port->ops->get_mctrl(port) & TIOCM_CAR)
+                spin_lock_irq(&port->lock);
+                mctrl = port->ops->get_mctrl(port);
+                spin_unlock_irq(&port->lock);
+                if (mctrl & TIOCM_CAR)
                         break;
 
                 up(&state->sem);
@@ -1618,7 +1625,9 @@ static int uart_line_info(char *buf, struct uart_driver *drv, int i)
 
         if(capable(CAP_SYS_ADMIN))
         {
+                spin_lock_irq(&port->lock);
                 status = port->ops->get_mctrl(port);
+                spin_unlock_irq(&port->lock);
 
                 ret += sprintf(buf + ret, " tx:%d rx:%d",
                                 port->icount.tx, port->icount.rx);