From 1e6651638b35fa10a91f1a45ebb9d9ff72baec1d Mon Sep 17 00:00:00 2001 From: Andre Naujoks Date: Fri, 13 Sep 2013 19:37:11 +0200 Subject: [PATCH] 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 "524693f1511708c427f893bdf1008fb4e97cb6ec 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 Acked-by: Oliver Hartkopp Acked-by: Marc Kleine-Budde Signed-off-by: David S. Miller --- drivers/net/can/slcan.c | 3 +++ drivers/net/slip/slip.c | 3 +++ 2 files changed, 6 insertions(+) diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c index 874188ba06f71..d571e2e9708f4 100644 --- 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 a34d6bf5e43b5..cc70ecfc70626 100644 --- 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) -- 2.39.5