serial: mrst_max3110: Fix race condition between spi transfers

There is a race between termios configuration and xmit that can cause the
intel_mid_ssp_spi driver to stall.

Serializing spi transactions fixes the problem.

Signed-off-by: Bin Gao <bin.gao@intel.com>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/tty/serial/mrst_max3110.c b/drivers/tty/serial/mrst_max3110.c
index ee77e7366ed6..565779dc7aac 100644
--- a/drivers/tty/serial/mrst_max3110.c
+++ b/drivers/tty/serial/mrst_max3110.c
@@ -61,6 +61,7 @@ struct uart_max3110 {
         struct task_struct *main_thread;
         struct task_struct *read_thread;
         struct mutex thread_mutex;
+        struct mutex io_mutex;
 
         u32 baud;
         u16 cur_conf;
@@ -90,6 +91,7 @@ static int max3110_write_then_read(struct uart_max3110 *max,
         struct spi_transfer     x;
         int ret;
 
+        mutex_lock(&max->io_mutex);
         spi_message_init(&message);
         memset(&x, 0, sizeof x);
         x.len = len;
@@ -104,6 +106,7 @@ static int max3110_write_then_read(struct uart_max3110 *max,
 
         /* Do the i/o */
         ret = spi_sync(spi, &message);
+        mutex_unlock(&max->io_mutex);
         return ret;
 }
 
@@ -805,6 +808,7 @@ static int serial_m3110_probe(struct spi_device *spi)
         max->irq = (u16)spi->irq;
 
         mutex_init(&max->thread_mutex);
+        mutex_init(&max->io_mutex);
 
         max->word_7bits = 0;
         max->parity = 0;