__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 taking port lock before
call of serial8250_tx_dma.
Moreover it moves the "dma->tx_running = 0" after updating
tail index to avoid any dma tx with obsolete data.
The best solution should consist in locking the port for
all the function life. however, doing this leads to random
platform freezes. don't know why.
While waiting to get a better fix, this patch does the
job and avoid any perilous concurrent dma tx.
Signed-off-by: Loic Poulain <loic.poulain@xxxxxxxxx>
---
drivers/tty/serial/8250/8250_dma.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index 7046769..3a7b89f 100644
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -20,8 +20,7 @@ static void __dma_tx_complete(void *param)
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);
@@ -30,11 +29,16 @@ static void __dma_tx_complete(void *param)
xmit->tail &= UART_XMIT_SIZE - 1;
p->port.icount.tx += dma->tx_size;
+ dma->tx_running = 0;
+
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(&p->port);
- if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port))
+ if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port)) {
+ spin_lock_irqsave(&p->port.lock, flags);
serial8250_tx_dma(p);
+ spin_unlock_irqrestore(&p->port.lock, flags);
+ }
}
static void __dma_rx_complete(void *param)
--
1.8.3.2
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