From cc9fa74e2a195f7bab27fbbc4896d2fe3ec32150 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 "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 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 874188ba06f7..d571e2e9708f 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 a34d6bf5e43b..cc70ecfc7062 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) -- 2.20.1