pkt_sched: Add 'deactivated' state.

This new state lets dev_deactivate() mark a qdisc as having been
deactivated.

dev_queue_xmit() and ing_filter() check for this bit and do not
try to process the qdisc if the bit is set.

dev_deactivate() polls the qdisc after setting the bit, waiting
for both __QDISC_STATE_RUNNING and __QDISC_STATE_SCHED to clear.

This isn't perfect yet, but subsequent changesets will make it so.
This part is just one piece of the puzzle.

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

2 files changed, 14 insertions, 1 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 600bb23c4c2e..d9e31f63aded 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1800,6 +1800,12 @@ gso:
 
                 spin_lock(root_lock);
 
+                if (unlikely(test_bit(__QDISC_STATE_DEACTIVATED, &q->state))) {
+                        spin_unlock(root_lock);
+                        rc = NET_XMIT_DROP;
+                        goto out_kfree_skb;
+                }
+
                 rc = qdisc_enqueue_root(skb, q);
                 qdisc_run(q);
 
@@ -2084,7 +2090,8 @@ static int ing_filter(struct sk_buff *skb)
         q = rxq->qdisc;
         if (q != &noop_qdisc) {
                 spin_lock(qdisc_lock(q));
-                result = qdisc_enqueue_root(skb, q);
+                if (likely(!test_bit(__QDISC_STATE_DEACTIVATED, &q->state)))
+                        result = qdisc_enqueue_root(skb, q);
                 spin_unlock(qdisc_lock(q));
         }
 
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 468574682caa..ff1c4557e5f8 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -597,6 +597,9 @@ static void transition_one_qdisc(struct net_device *dev,
         struct Qdisc *new_qdisc = dev_queue->qdisc_sleeping;
         int *need_watchdog_p = _need_watchdog;
 
+        if (!(new_qdisc->flags & TCQ_F_BUILTIN))
+                clear_bit(__QDISC_STATE_DEACTIVATED, &new_qdisc->state);
+
         rcu_assign_pointer(dev_queue->qdisc, new_qdisc);
         if (need_watchdog_p && new_qdisc != &noqueue_qdisc)
                 *need_watchdog_p = 1;
@@ -640,6 +643,9 @@ static void dev_deactivate_queue(struct net_device *dev,
         if (qdisc) {
                 spin_lock_bh(qdisc_lock(qdisc));
 
+                if (!(qdisc->flags & TCQ_F_BUILTIN))
+                        set_bit(__QDISC_STATE_DEACTIVATED, &qdisc->state);
+
                 dev_queue->qdisc = qdisc_default;
                 qdisc_reset(qdisc);