From: David Miller

Date: Mon, 18 Aug 2008 17:11:24 -0700 (PDT)
> Especially since we've bullet-proof'd dev_deactivate(), there

quoted text
> should be absolutely no more references to the qdisc any

> longer.

>

> I'll look into doing it this way, thanks.

Ok, here it is.  I'll push this out to net-2.6 after I do

some testing here.
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

---

 net/sched/sch_api.c     |   13 ++-----------

 net/sched/sch_generic.c |    6 ------

 2 files changed, 2 insertions(+), 17 deletions(-)
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c

index 7d7070b..d91a233 100644

--- a/net/sched/sch_api.c

+++ b/net/sched/sch_api.c

@@ -638,11 +638,8 @@ static void notify_and_destroy(struct sk_buff *skb, struct nlmsghdr *n, u32 clid

 	if (new || old)

 		qdisc_notify(skb, n, clid, old, new);
-	if (old) {

-		sch_tree_lock(old);

+	if (old)

 		qdisc_destroy(old);

-		sch_tree_unlock(old);

-	}

 }
 /* Graft qdisc "new" to class "classid" of qdisc "parent" or

@@ -1092,16 +1089,10 @@ create_n_graft:
 graft:

 	if (1) {

-		spinlock_t *root_lock;

-

 		err = qdisc_graft(dev, p, skb, n, clid, q, NULL);

 		if (err) {

-			if (q) {

-				root_lock = qdisc_root_lock(q);

-				spin_lock_bh(root_lock);

+			if (q)

 				qdisc_destroy(q);

-				spin_unlock_bh(root_lock);

-			}

 			return err;

 		}

 	}

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c

index 6f96b7b..c3ed4d4 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);

 	}

 }
--

1.5.6.5.GIT
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