[NETEM]: avoid excessive requeues

The netem code would call getnstimeofday() and dequeue/requeue after
every packet, even if it was waiting. Avoid this overhead by using
the throttled flag.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index b06f202..fcaa4ad 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -298,6 +298,7 @@
 						 timer);
 
 	wd->qdisc->flags &= ~TCQ_F_THROTTLED;
+	smp_wmb();
 	netif_schedule(wd->qdisc->dev);
 	return HRTIMER_NORESTART;
 }
@@ -315,6 +316,7 @@
 	ktime_t time;
 
 	wd->qdisc->flags |= TCQ_F_THROTTLED;
+	smp_wmb();
 	time = ktime_set(0, 0);
 	time = ktime_add_ns(time, PSCHED_US2NS(expires));
 	hrtimer_start(&wd->timer, time, HRTIMER_MODE_ABS);
@@ -325,6 +327,7 @@
 {
 	hrtimer_cancel(&wd->timer);
 	wd->qdisc->flags &= ~TCQ_F_THROTTLED;
+	smp_wmb();
 }
 EXPORT_SYMBOL(qdisc_watchdog_cancel);