net: add a generic tracepoint for TX queue timeout

Although devlink health report does a nice job on reporting TX
timeout and other NIC errors, unfortunately it requires drivers
to support it but currently only mlx5 has implemented it.
Before other drivers could catch up, it is useful to have a
generic tracepoint to monitor this kind of TX timeout. We have
been suffering TX timeout with different drivers, we plan to
start to monitor it with rasdaemon which just needs a new tracepoint.

Sample output:

  ksoftirqd/1-16    [001] ..s2   144.043173: net_dev_xmit_timeout: dev=ens3 driver=e1000 queue=0

Cc: Eran Ben Elisha <[email protected]>
Cc: Jiri Pirko <[email protected]>
Signed-off-by: Cong Wang <[email protected]>
Acked-by: Jiri Pirko <[email protected]>
Reviewed-by: Eran Ben Elisha <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

include/trace/events/net.h

@@ -95,6 +95,29 @@ TRACE_EVENT(net_dev_xmit,
 		__get_str(name), __entry->skbaddr, __entry->len, __entry->rc)
 );
 
+TRACE_EVENT(net_dev_xmit_timeout,
+
+	TP_PROTO(struct net_device *dev,
+		 int queue_index),
+
+	TP_ARGS(dev, queue_index),
+
+	TP_STRUCT__entry(
+		__string(	name,		dev->name	)
+		__string(	driver,		netdev_drivername(dev))
+		__field(	int,		queue_index	)
+	),
+
+	TP_fast_assign(
+		__assign_str(name, dev->name);
+		__assign_str(driver, netdev_drivername(dev));
+		__entry->queue_index = queue_index;
+	),
+
+	TP_printk("dev=%s driver=%s queue=%d",
+		__get_str(name), __get_str(driver), __entry->queue_index)
+);
+
 DECLARE_EVENT_CLASS(net_dev_template,
 
 	TP_PROTO(struct sk_buff *skb),

net/sched/sch_generic.c

@@ -32,6 +32,7 @@
 #include <net/pkt_sched.h>
 #include <net/dst.h>
 #include <trace/events/qdisc.h>
+#include <trace/events/net.h>
 #include <net/xfrm.h>
 
 /* Qdisc to use by default */
@@ -441,6 +442,7 @@ static void dev_watchdog(struct timer_list *t)
 			}
 
 			if (some_queue_timedout) {
+				trace_net_dev_xmit_timeout(dev, i);
 				WARN_ONCE(1, KERN_INFO "NETDEV WATCHDOG: %s (%s): transmit queue %u timed out\n",
 				       dev->name, netdev_drivername(dev), i);
 				dev->netdev_ops->ndo_tx_timeout(dev);