pkt_sched: Check the state of tx_queue in dequeue_skb()

Check in dequeue_skb() the state of tx_queue for requeued skb to save
on locking and re-requeuing, and possibly remove the current check in
qdisc_run(). Based on the idea of Alexander Duyck.

Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 4 deletions

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 1b508bd1c06c..5e7e0bd38fe8 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -52,11 +52,21 @@ static inline int dev_requeue_skb(struct sk_buff *skb, struct Qdisc *q)
 
 static inline struct sk_buff *dequeue_skb(struct Qdisc *q)
 {
-        struct sk_buff *skb;
-
-        skb = __skb_dequeue(&q->requeue);
-        if (!skb)
+        struct sk_buff *skb = skb_peek(&q->requeue);
+
+        if (unlikely(skb)) {
+                struct net_device *dev = qdisc_dev(q);
+                struct netdev_queue *txq;
+
+                /* check the reason of requeuing without tx lock first */
+                txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
+                if (!netif_tx_queue_stopped(txq) && !netif_tx_queue_frozen(txq))
+                        __skb_unlink(skb, &q->requeue);
+                else
+                        skb = NULL;
+        } else {
                 skb = q->dequeue(q);
+        }
 
         return skb;
 }