serial-uartlite: fix missing locking in isr

The uartlite driver suffers from missing/duplicate/corrupted character
data when the interrupt handler runs concurrently with access to the
device from another cpu. Take the port spinlock to exclude concurrent
access.

Signed-off-by: Rich Felker <dalias@libc.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/tty/serial/uartlite.c b/drivers/tty/serial/uartlite.c
index c249aee887d2..ee2e8efdea4a 100644
--- a/drivers/tty/serial/uartlite.c
+++ b/drivers/tty/serial/uartlite.c
@@ -194,7 +194,9 @@ static irqreturn_t ulite_isr(int irq, void *dev_id)
 {
         struct uart_port *port = dev_id;
         int busy, n = 0;
+        unsigned long flags;
 
+        spin_lock_irqsave(&port->lock, flags);
         do {
                 int stat = uart_in32(ULITE_STATUS, port);
                 busy  = ulite_receive(port, stat);
@@ -202,6 +204,8 @@ static irqreturn_t ulite_isr(int irq, void *dev_id)
                 n++;
         } while (busy);
 
+        spin_unlock_irqrestore(&port->lock, flags);
+
         /* work done? */
         if (n > 1) {
                 tty_flip_buffer_push(&port->state->port);