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>

diff --git a/drivers/tty/serial/mrst_max3110.c b/drivers/tty/serial/mrst_max3110.c
index ee77e7366ed6ffad4420a4e57694a7b6d1cbc865..565779dc7aac80c6a8ce7a20ac53bc6ef76c56fb 100644 (file)
--- 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;