net: qdisc: use rcu prefix and silence sparse warnings

Add __rcu notation to qdisc handling by doing this we can make
smatch output more legible. And anyways some of the cases should
be using rcu_dereference() see qdisc_all_tx_empty(),
qdisc_tx_chainging(), and so on.

Also *wake_queue() API is commonly called from driver timer routines
without rcu lock or rtnl lock. So I added rcu_read_lock() blocks
around netif_wake_subqueue and netif_tx_wake_queue.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 6 deletions

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index a3cfb8ebeb53..56838ab29b42 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -259,7 +259,9 @@ static inline spinlock_t *qdisc_lock(struct Qdisc *qdisc)
 
 static inline struct Qdisc *qdisc_root(const struct Qdisc *qdisc)
 {
-        return qdisc->dev_queue->qdisc;
+        struct Qdisc *q = rcu_dereference_rtnl(qdisc->dev_queue->qdisc);
+
+        return q;
 }
 
 static inline struct Qdisc *qdisc_root_sleeping(const struct Qdisc *qdisc)
@@ -384,7 +386,7 @@ static inline void qdisc_reset_all_tx_gt(struct net_device *dev, unsigned int i)
         struct Qdisc *qdisc;
 
         for (; i < dev->num_tx_queues; i++) {
-                qdisc = netdev_get_tx_queue(dev, i)->qdisc;
+                qdisc = rtnl_dereference(netdev_get_tx_queue(dev, i)->qdisc);
                 if (qdisc) {
                         spin_lock_bh(qdisc_lock(qdisc));
                         qdisc_reset(qdisc);
@@ -402,13 +404,18 @@ static inline void qdisc_reset_all_tx(struct net_device *dev)
 static inline bool qdisc_all_tx_empty(const struct net_device *dev)
 {
         unsigned int i;
+
+        rcu_read_lock();
         for (i = 0; i < dev->num_tx_queues; i++) {
                 struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
-                const struct Qdisc *q = txq->qdisc;
+                const struct Qdisc *q = rcu_dereference(txq->qdisc);
 
-                if (q->q.qlen)
+                if (q->q.qlen) {
+                        rcu_read_unlock();
                         return false;
+                }
         }
+        rcu_read_unlock();
         return true;
 }
 
@@ -416,9 +423,10 @@ static inline bool qdisc_all_tx_empty(const struct net_device *dev)
 static inline bool qdisc_tx_changing(const struct net_device *dev)
 {
         unsigned int i;
+
         for (i = 0; i < dev->num_tx_queues; i++) {
                 struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
-                if (txq->qdisc != txq->qdisc_sleeping)
+                if (rcu_access_pointer(txq->qdisc) != txq->qdisc_sleeping)
                         return true;
         }
         return false;
@@ -428,9 +436,10 @@ static inline bool qdisc_tx_changing(const struct net_device *dev)
 static inline bool qdisc_tx_is_noop(const struct net_device *dev)
 {
         unsigned int i;
+
         for (i = 0; i < dev->num_tx_queues; i++) {
                 struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
-                if (txq->qdisc != &noop_qdisc)
+                if (rcu_access_pointer(txq->qdisc) != &noop_qdisc)
                         return false;
         }
         return true;