[PATCH 3.10 011/103] serial: 8250: Fix thread unsafe __dma_tx_complete function

Greg Kroah-Hartman
2014-06-04T23:47:31Z

From: Loic Poulain <loic.poulain@intel.com>

commit f8fd1b0350d3a4581125f5eda6528f5a2c5f9183 upstream.

__dma_tx_complete is not protected against concurrent
call of serial8250_tx_dma. it can lead to circular tail
index corruption or parallel call of serial_tx_dma on the
same data portion.

This patch fixes this issue by holding the port lock.

Signed-off-by: Loic Poulain <loic.poulain@intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/tty/serial/8250/8250_dma.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -20,12 +20,15 @@ static void __dma_tx_complete(void *para
struct uart_8250_port *p = param;
struct uart_8250_dma *dma = p->dma;
struct circ_buf *xmit = &p->port.state->xmit;
-
- dma->tx_running = 0;
+ unsigned long flags;

dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
UART_XMIT_SIZE, DMA_TO_DEVICE);

+ spin_lock_irqsave(&p->port.lock, flags);
+
+ dma->tx_running = 0;
+
xmit->tail += dma->tx_size;
xmit->tail &= UART_XMIT_SIZE - 1;
p->port.icount.tx += dma->tx_size;
@@ -35,6 +38,8 @@ static void __dma_tx_complete(void *para

if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port))
serial8250_tx_dma(p);
+
+ spin_unlock_irqrestore(&p->port.lock, flags);
}

static void __dma_rx_complete(void *param)