pkt_sched: Never schedule non-root qdiscs.

Based upon initial discovery and patch by Jarek Poplawski.

The qdisc watchdogs can be attached to any qdisc, not just the root,
so make sure we schedule the correct one.

CBQ has a similar bug.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/sch_api.c

@@ -426,7 +426,7 @@ static enum hrtimer_restart qdisc_watchdog(struct hrtimer *timer)
 
 	wd->qdisc->flags &= ~TCQ_F_THROTTLED;
 	smp_wmb();
-	__netif_schedule(wd->qdisc);
+	__netif_schedule(qdisc_root(wd->qdisc));
 
 	return HRTIMER_NORESTART;
 }

net/sched/sch_cbq.c

@@ -654,7 +654,7 @@ static enum hrtimer_restart cbq_undelay(struct hrtimer *timer)
 	}
 
 	sch->flags &= ~TCQ_F_THROTTLED;
-	__netif_schedule(sch);
+	__netif_schedule(qdisc_root(sch));
 	return HRTIMER_NORESTART;
 }