net: Change handling of the __QDISC_STATE_SCHED flag in net_tx_action().

Change handling of the __QDISC_STATE_SCHED flag in net_tx_action() to
enable proper control in dev_deactivate(). Now, if this flag is seen
as unset under root_lock means a qdisc can't be netif_scheduled.
Signed-off-by: NJarek Poplawski <jarkao2@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -1339,19 +1339,23 @@ static void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev)
 }
 
 
-void __netif_schedule(struct Qdisc *q)
+static inline void __netif_reschedule(struct Qdisc *q)
 {
-	if (!test_and_set_bit(__QDISC_STATE_SCHED, &q->state)) {
-		struct softnet_data *sd;
-		unsigned long flags;
+	struct softnet_data *sd;
+	unsigned long flags;
 
-		local_irq_save(flags);
-		sd = &__get_cpu_var(softnet_data);
-		q->next_sched = sd->output_queue;
-		sd->output_queue = q;
-		raise_softirq_irqoff(NET_TX_SOFTIRQ);
-		local_irq_restore(flags);
-	}
+	local_irq_save(flags);
+	sd = &__get_cpu_var(softnet_data);
+	q->next_sched = sd->output_queue;
+	sd->output_queue = q;
+	raise_softirq_irqoff(NET_TX_SOFTIRQ);
+	local_irq_restore(flags);
+}
+
+void __netif_schedule(struct Qdisc *q)
+{
+	if (!test_and_set_bit(__QDISC_STATE_SCHED, &q->state))
+		__netif_reschedule(q);
 }
 EXPORT_SYMBOL(__netif_schedule);
 
@@ -1980,15 +1984,15 @@ static void net_tx_action(struct softirq_action *h)
 
 			head = head->next_sched;
 
-			smp_mb__before_clear_bit();
-			clear_bit(__QDISC_STATE_SCHED, &q->state);
-
 			root_lock = qdisc_lock(q);
 			if (spin_trylock(root_lock)) {
+				smp_mb__before_clear_bit();
+				clear_bit(__QDISC_STATE_SCHED,
+					  &q->state);
 				qdisc_run(q);
 				spin_unlock(root_lock);
 			} else {
-				__netif_schedule(q);
+				__netif_reschedule(q);
 			}
 		}
 	}