pkt_sched: Add and use qdisc_root() and qdisc_root_lock().

When code wants to lock the qdisc tree state, the logic
operation it's doing is locking the top-level qdisc that
sits of the root of the netdev_queue.

Add qdisc_root_lock() to represent this and convert the
easiest cases.

In order for this to work out in all cases, we have to
hook up the noop_qdisc to a dummy netdev_queue.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 4 deletions

diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c
index 4efc836cbf38..37ae653db683 100644
--- a/net/sched/sch_cbq.c
+++ b/net/sched/sch_cbq.c
@@ -1744,12 +1744,13 @@ static void cbq_put(struct Qdisc *sch, unsigned long arg)
 
         if (--cl->refcnt == 0) {
 #ifdef CONFIG_NET_CLS_ACT
+                spinlock_t *root_lock = qdisc_root_lock(sch);
                 struct cbq_sched_data *q = qdisc_priv(sch);
 
-                spin_lock_bh(&sch->dev_queue->lock);
+                spin_lock_bh(root_lock);
                 if (q->rx_class == cl)
                         q->rx_class = NULL;
-                spin_unlock_bh(&sch->dev_queue->lock);
+                spin_unlock_bh(root_lock);
 #endif
 
                 cbq_destroy_class(sch, cl);
@@ -1828,7 +1829,7 @@ cbq_change_class(struct Qdisc *sch, u32 classid, u32 parentid, struct nlattr **t
 
                 if (tca[TCA_RATE])
                         gen_replace_estimator(&cl->bstats, &cl->rate_est,
-                                              &sch->dev_queue->lock,
+                                              qdisc_root_lock(sch),
                                               tca[TCA_RATE]);
                 return 0;
         }
@@ -1919,7 +1920,7 @@ cbq_change_class(struct Qdisc *sch, u32 classid, u32 parentid, struct nlattr **t
 
         if (tca[TCA_RATE])
                 gen_new_estimator(&cl->bstats, &cl->rate_est,
-                                  &sch->dev_queue->lock, tca[TCA_RATE]);
+                                  qdisc_root_lock(sch), tca[TCA_RATE]);
 
         *arg = (unsigned long)cl;
         return 0;