[SERIAL] Fix clocal wakeup problem

Jim Alexander reported a problem where "if one calls open() in
blocking mode with CLOCAL off, the 8250.c driver under the 2.6
kernel (or at least 2.6.8 and 2.6.10) does not wake up the
blocked process when DCD is asserted."

Fix this by enabling modem status interrupts immediately before
we read the carrier detect status.

Thanks to Jim for reporting the problem and testing the fix.

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

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 34c576dfad8d..9589509fc5bd 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -1440,6 +1440,7 @@ uart_block_til_ready(struct file *filp, struct uart_state *state)
                  * modem is ready for us.
                  */
                 spin_lock_irq(&port->lock);
+                port->ops->enable_ms(port);
                 mctrl = port->ops->get_mctrl(port);
                 spin_unlock_irq(&port->lock);
                 if (mctrl & TIOCM_CAR)