can: slcan: Fix spinlock variant

slc_xmit is called within softirq context and locks sl->lock, but
slcan_write_wakeup is not softirq context, so we need to use
spin_[un]lock_bh!
Detected using kernel lock debugging mechanism.

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c
index f5b16e0..dcf9196 100644 (file)
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -322,13 +322,13 @@ static void slcan_write_wakeup(struct tty_struct *tty)
        if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
                return;
 
-       spin_lock(&sl->lock);
+       spin_lock_bh(&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);
+               spin_unlock_bh(&sl->lock);
                netif_wake_queue(sl->dev);
                return;
        }
@@ -336,7 +336,7 @@ 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);
+       spin_unlock_bh(&sl->lock);
 }
 
 /* Send a can_frame to a TTY queue. */