net_sched: get rid of unnecessary dev_qdisc_reset()

Resetting old qdisc on dev_queue->qdisc_sleeping in
dev_qdisc_reset() is redundant, because this qdisc,
even if not same with dev_queue->qdisc, is reset via
qdisc_put() right after calling dev_graft_qdisc() when
hitting refcnt 0.

This is very easy to observe with qdisc_reset() tracepoint
and stack traces.

Reported-by: Václav Zindulka <vaclav.zindulka@tlapnet.cz>
Tested-by: Václav Zindulka <vaclav.zindulka@tlapnet.cz>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index d13e27467470d1abcd5c99870197d45ee4f7889b..b19a0021a0bd1a7e20721690402952ae26bb68b6 100644 (file)
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -1191,16 +1191,6 @@ static bool some_qdisc_is_busy(struct net_device *dev)
        return false;
 }
 
-static void dev_qdisc_reset(struct net_device *dev,
-                           struct netdev_queue *dev_queue,
-                           void *none)
-{
-       struct Qdisc *qdisc = dev_queue->qdisc_sleeping;
-
-       if (qdisc)
-               qdisc_reset(qdisc);
-}
-
 /**
  *     dev_deactivate_many - deactivate transmissions on several devices
  *     @head: list of devices to deactivate
@@ -1237,12 +1227,6 @@ void dev_deactivate_many(struct list_head *head)
                         */
                        schedule_timeout_uninterruptible(1);
                }
-               /* The new qdisc is assigned at this point so we can safely
-                * unwind stale skb lists and qdisc statistics
-                */
-               netdev_for_each_tx_queue(dev, dev_qdisc_reset, NULL);
-               if (dev_ingress_queue(dev))
-                       dev_qdisc_reset(dev, dev_ingress_queue(dev), NULL);
        }
 }