slip/slcan: added locking in wakeup function

The locking is needed, since the the internal buffer for the CAN frames is
changed during the wakeup call. This could cause buffer inconsistencies
under high loads, especially for the outgoing short CAN packet skbuffs.

The needed locks led to deadlocks before commit
"5ede52538ee2b2202d9dff5b06c33bfde421e6e4 tty: Remove extra wakeup from pty
write() path", which removed the direct callback to the wakeup function from the
tty layer.

As slcan.c is based on slip.c the issue in the original code is fixed, too.

Signed-off-by: Andre Naujoks <nautsch2@gmail.com>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Acked-by: Marc Kleine-Budde  <mkl@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c
index 874188ba06f7172fed36b93db05be06ae0e2bd59..d571e2e9708f4cd8fbd862b582446c1e6efae40d 100644 (file)
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -286,11 +286,13 @@ static void slcan_write_wakeup(struct tty_struct *tty)
        if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
                return;
 
+       spin_lock(&sl->lock);
        if (sl->xleft <= 0)  {
                /* Now serial buffer is almost free & we can start
                 * transmission of another packet */
                sl->dev->stats.tx_packets++;
                clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+               spin_unlock(&sl->lock);
                netif_wake_queue(sl->dev);
                return;
        }
@@ -298,6 +300,7 @@ static void slcan_write_wakeup(struct tty_struct *tty)
        actual = tty->ops->write(tty, sl->xhead, sl->xleft);
        sl->xleft -= actual;
        sl->xhead += actual;
+       spin_unlock(&sl->lock);
 }
 
 /* Send a can_frame to a TTY queue. */

diff --git a/drivers/net/slip/slip.c b/drivers/net/slip/slip.c
index a34d6bf5e43b5b29325215e358cca9ee3fc734ee..cc70ecfc70626789183e462c8b51d13f0c7fc8aa 100644 (file)
--- a/drivers/net/slip/slip.c
+++ b/drivers/net/slip/slip.c
@@ -429,11 +429,13 @@ static void slip_write_wakeup(struct tty_struct *tty)
        if (!sl || sl->magic != SLIP_MAGIC || !netif_running(sl->dev))
                return;
 
+       spin_lock(&sl->lock);
        if (sl->xleft <= 0)  {
                /* Now serial buffer is almost free & we can start
                 * transmission of another packet */
                sl->dev->stats.tx_packets++;
                clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+               spin_unlock(&sl->lock);
                sl_unlock(sl);
                return;
        }
@@ -441,6 +443,7 @@ static void slip_write_wakeup(struct tty_struct *tty)
        actual = tty->ops->write(tty, sl->xhead, sl->xleft);
        sl->xleft -= actual;
        sl->xhead += actual;
+       spin_unlock(&sl->lock);
 }
 
 static void sl_tx_timeout(struct net_device *dev)