net: new counter for tx_timeout errors in sysfs

This adds the /sys/class/net/DEV/queues/Q/tx_timeout attribute
containing the total number of timeout events on the given queue. It
is always available with CONFIG_SYSFS, independently of
CONFIG_RPS/XPS.

Credits to Stephen Hemminger for a preliminary version of this patch.

Tested:
  without CONFIG_SYSFS (compilation only)
  with sysfs and without CONFIG_RPS & CONFIG_XPS
  with sysfs and without CONFIG_RPS
  with sysfs and without CONFIG_XPS
  with defaults
Signed-off-by: David Decotigny <david.decotigny@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -532,7 +532,7 @@ struct netdev_queue {
 	struct Qdisc		*qdisc;
 	unsigned long		state;
 	struct Qdisc		*qdisc_sleeping;
-#if defined(CONFIG_RPS) || defined(CONFIG_XPS)
+#ifdef CONFIG_SYSFS
 	struct kobject		kobj;
 #endif
 #if defined(CONFIG_XPS) && defined(CONFIG_NUMA)
@@ -547,6 +547,12 @@ struct netdev_queue {
 	 * please use this field instead of dev->trans_start
 	 */
 	unsigned long		trans_start;
+
+	/*
+	 * Number of TX timeouts for this queue
+	 * (/sys/class/net/DEV/Q/trans_timeout)
+	 */
+	unsigned long		trans_timeout;
 } ____cacheline_aligned_in_smp;
 
 static inline int netdev_queue_numa_node_read(const struct netdev_queue *q)
@@ -1109,9 +1115,11 @@ struct net_device {
 
 	unsigned char		broadcast[MAX_ADDR_LEN];	/* hw bcast add	*/
 
-#if defined(CONFIG_RPS) || defined(CONFIG_XPS)
+#ifdef CONFIG_SYSFS
 	struct kset		*queues_kset;
+#endif
 
+#ifdef CONFIG_RPS
 	struct netdev_rx_queue	*_rx;
 
 	/* Number of RX queues allocated at register_netdev() time */

net/core/net-sysfs.c

@@ -780,7 +780,7 @@ net_rx_queue_update_kobjects(struct net_device *net, int old_num, int new_num)
 #endif
 }
 
-#ifdef CONFIG_XPS
+#ifdef CONFIG_SYSFS
 /*
  * netdev_queue sysfs structures and functions.
  */
@@ -826,6 +826,23 @@ static const struct sysfs_ops netdev_queue_sysfs_ops = {
 	.store = netdev_queue_attr_store,
 };
 
+static ssize_t show_trans_timeout(struct netdev_queue *queue,
+				  struct netdev_queue_attribute *attribute,
+				  char *buf)
+{
+	unsigned long trans_timeout;
+
+	spin_lock_irq(&queue->_xmit_lock);
+	trans_timeout = queue->trans_timeout;
+	spin_unlock_irq(&queue->_xmit_lock);
+
+	return sprintf(buf, "%lu", trans_timeout);
+}
+
+static struct netdev_queue_attribute queue_trans_timeout =
+	__ATTR(tx_timeout, S_IRUGO, show_trans_timeout, NULL);
+
+#ifdef CONFIG_XPS
 static inline unsigned int get_netdev_queue_index(struct netdev_queue *queue)
 {
 	struct net_device *dev = queue->dev;
@@ -1020,12 +1037,17 @@ static ssize_t store_xps_map(struct netdev_queue *queue,
 
 static struct netdev_queue_attribute xps_cpus_attribute =
     __ATTR(xps_cpus, S_IRUGO | S_IWUSR, show_xps_map, store_xps_map);
+#endif /* CONFIG_XPS */
 
 static struct attribute *netdev_queue_default_attrs[] = {
+	&queue_trans_timeout.attr,
+#ifdef CONFIG_XPS
 	&xps_cpus_attribute.attr,
+#endif
 	NULL
 };
 
+#ifdef CONFIG_XPS
 static void netdev_queue_release(struct kobject *kobj)
 {
 	struct netdev_queue *queue = to_netdev_queue(kobj);
@@ -1076,10 +1098,13 @@ static void netdev_queue_release(struct kobject *kobj)
 	memset(kobj, 0, sizeof(*kobj));
 	dev_put(queue->dev);
 }
+#endif /* CONFIG_XPS */
 
 static struct kobj_type netdev_queue_ktype = {
 	.sysfs_ops = &netdev_queue_sysfs_ops,
+#ifdef CONFIG_XPS
 	.release = netdev_queue_release,
+#endif
 	.default_attrs = netdev_queue_default_attrs,
 };
 
@@ -1102,12 +1127,12 @@ static int netdev_queue_add_kobject(struct net_device *net, int index)
 
 	return error;
 }
-#endif /* CONFIG_XPS */
+#endif /* CONFIG_SYSFS */
 
 int
 netdev_queue_update_kobjects(struct net_device *net, int old_num, int new_num)
 {
-#ifdef CONFIG_XPS
+#ifdef CONFIG_SYSFS
 	int i;
 	int error = 0;
 
@@ -1125,14 +1150,14 @@ netdev_queue_update_kobjects(struct net_device *net, int old_num, int new_num)
 	return error;
 #else
 	return 0;
-#endif
+#endif /* CONFIG_SYSFS */
 }
 
 static int register_queue_kobjects(struct net_device *net)
 {
 	int error = 0, txq = 0, rxq = 0, real_rx = 0, real_tx = 0;
 
-#if defined(CONFIG_RPS) || defined(CONFIG_XPS)
+#ifdef CONFIG_SYSFS
 	net->queues_kset = kset_create_and_add("queues",
 	    NULL, &net->dev.kobj);
 	if (!net->queues_kset)
@@ -1173,7 +1198,7 @@ static void remove_queue_kobjects(struct net_device *net)
 
 	net_rx_queue_update_kobjects(net, real_rx, 0);
 	netdev_queue_update_kobjects(net, real_tx, 0);
-#if defined(CONFIG_RPS) || defined(CONFIG_XPS)
+#ifdef CONFIG_SYSFS
 	kset_unregister(net->queues_kset);
 #endif
 }

net/sched/sch_generic.c

@@ -246,6 +246,7 @@ static void dev_watchdog(unsigned long arg)
 				    time_after(jiffies, (trans_start +
 							 dev->watchdog_timeo))) {
 					some_queue_timedout = 1;
+					txq->trans_timeout++;
 					break;
 				}
 			}