pkt_sched: No longer destroy qdiscs from RCU.

We can now kill them synchronously with all of the
previous dev_deactivate() cures.

This makes netdev destruction and shutdown saner as
the qdiscs hold references to the device.
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sch_generic.h

@@ -61,7 +61,6 @@ struct Qdisc
 	struct gnet_stats_basic	bstats;
 	struct gnet_stats_queue	qstats;
 	struct gnet_stats_rate_est	rate_est;
-	struct rcu_head 	q_rcu;
 	int			(*reshape_fail)(struct sk_buff *skb,
 					struct Qdisc *q);
 

net/sched/sch_generic.c

@@ -518,14 +518,19 @@ void qdisc_reset(struct Qdisc *qdisc)
 }
 EXPORT_SYMBOL(qdisc_reset);
 
-/* this is the rcu callback function to clean up a qdisc when there
- * are no further references to it */
+/* Under qdisc_lock(qdisc) and BH! */
 
-static void __qdisc_destroy(struct rcu_head *head)
+void qdisc_destroy(struct Qdisc *qdisc)
 {
-	struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);
 	const struct Qdisc_ops  *ops = qdisc->ops;
 
+	if (qdisc->flags & TCQ_F_BUILTIN ||
+	    !atomic_dec_and_test(&qdisc->refcnt))
+		return;
+
+	if (qdisc->parent)
+		list_del(&qdisc->list);
+
 #ifdef CONFIG_NET_SCHED
 	qdisc_put_stab(qdisc->stab);
 #endif
@@ -542,20 +547,6 @@ static void __qdisc_destroy(struct rcu_head *head)
 
 	kfree((char *) qdisc - qdisc->padded);
 }
-
-/* Under qdisc_lock(qdisc) and BH! */
-
-void qdisc_destroy(struct Qdisc *qdisc)
-{
-	if (qdisc->flags & TCQ_F_BUILTIN ||
-	    !atomic_dec_and_test(&qdisc->refcnt))
-		return;
-
-	if (qdisc->parent)
-		list_del(&qdisc->list);
-
-	call_rcu(&qdisc->q_rcu, __qdisc_destroy);
-}
 EXPORT_SYMBOL(qdisc_destroy);
 
 static bool dev_all_qdisc_sleeping_noop(struct net_device *dev)