tegra_uart_rx_dma_complete (via DMA callback) and
tegra_uart_handle_rx_dma (via uart isr) can happen concurrently.
tegra_uart_rx_complete gives up the port lock temporarily to call
tty_flip_buffer_push. Since tegra_uart_start_rx_dma has not been
called yet in that context, tegra_uart_handle_rx_dma has the chance
to operate on the same DMA cookie. This allows for the same DMA
transaction to be processed twice.
The solution is to postpone tty_flip_buffer_push until after the next
DMA is started in both routines. That way when the lock is released
in either context, the other context will operate on a new DMA
transaction.
Signed-off-by: Christopher Freeman <cfreeman@xxxxxxxxxx>
---
drivers/tty/serial/serial-tegra.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
index cf0133a..f9bd378 100644
--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -606,12 +606,6 @@ static void tegra_uart_rx_dma_complete(void *args)
tegra_uart_copy_rx_to_tty(tup, port, count);
tegra_uart_handle_rx_pio(tup, port);
- if (tty) {
- spin_unlock_irqrestore(&u->lock, flags);
- tty_flip_buffer_push(port);
- spin_lock_irqsave(&u->lock, flags);
- tty_kref_put(tty);
- }
tegra_uart_start_rx_dma(tup);
/* Activate flow control to start transfer */
@@ -620,6 +614,10 @@ static void tegra_uart_rx_dma_complete(void *args)
done:
spin_unlock_irqrestore(&u->lock, flags);
+ if (tty) {
+ tty_flip_buffer_push(port);
+ tty_kref_put(tty);
+ }
}
static void tegra_uart_handle_rx_dma(struct tegra_uart_port *tup,
@@ -644,16 +642,17 @@ static void tegra_uart_handle_rx_dma(struct tegra_uart_port *tup,
tegra_uart_copy_rx_to_tty(tup, port, count);
tegra_uart_handle_rx_pio(tup, port);
+ tegra_uart_start_rx_dma(tup);
+
+ if (tup->rts_active)
+ set_rts(tup, true);
+
if (tty) {
spin_unlock_irqrestore(&u->lock, *flags);
tty_flip_buffer_push(port);
spin_lock_irqsave(&u->lock, *flags);
tty_kref_put(tty);
}
- tegra_uart_start_rx_dma(tup);
-
- if (tup->rts_active)
- set_rts(tup, true);
}
static int tegra_uart_start_rx_dma(struct tegra_uart_port *tup)
--
2.1.4
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