net: Add a WARN_ON_ONCE() to the transmit timeout function

WARN_ON_ONCE() gives a stack trace including the full module list.
Having this in the kernel dump for the timeout case in the
generic netdev watchdog will help us see quicker which driver
is involved. It also allows us to collect statistics 
and patterns in terms of which drivers have this event occuring.

Suggested by Andrew Morton

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index b741618e4d54..d355e5e47fe3 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -219,6 +219,7 @@ static void dev_watchdog(unsigned long arg)
                                 printk(KERN_INFO "NETDEV WATCHDOG: %s: transmit timed out\n",
                                        dev->name);
                                 dev->tx_timeout(dev);
+                                WARN_ON_ONCE(1);
                         }
                         if (!mod_timer(&dev->watchdog_timer, round_jiffies(jiffies + dev->watchdog_timeo)))
                                 dev_hold(dev);