pkt_sched: Don't hold qdisc lock over qdisc_destroy().

Based upon reports by Denys Fedoryshchenko, and feedback
and help from Jarek Poplawski and Herbert Xu.

We always either:

1) Never made an external reference to this qdisc.

or

2) Did a dev_deactivate() which purged all asynchronous
   references.

So do not lock the qdisc when we call qdisc_destroy(),
it's illegal anyways as when we drop the lock this is
free'd memory.

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

1 files changed, 0 insertions, 6 deletions

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 6f96b7bc080..c3ed4d44fc1 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -518,8 +518,6 @@ void qdisc_reset(struct Qdisc *qdisc)
 }
 EXPORT_SYMBOL(qdisc_reset);
 
-/* Under qdisc_lock(qdisc) and BH! */
-
 void qdisc_destroy(struct Qdisc *qdisc)
 {
 	const struct Qdisc_ops  *ops = qdisc->ops;
@@ -712,14 +710,10 @@ static void shutdown_scheduler_queue(struct net_device *dev,
 	struct Qdisc *qdisc_default = _qdisc_default;
 
 	if (qdisc) {
-		spinlock_t *root_lock = qdisc_lock(qdisc);
-
 		dev_queue->qdisc = qdisc_default;
 		dev_queue->qdisc_sleeping = qdisc_default;
 
-		spin_lock_bh(root_lock);
 		qdisc_destroy(qdisc);
-		spin_unlock_bh(root_lock);
 	}
 }