From 43effa1e57fc4635e0301b27d78f9d83afe78974 Mon Sep 17 00:00:00 2001 From: Patrick McHardy Date: Wed, 29 Nov 2006 17:35:48 -0800 Subject: [NET_SCHED]: Fix endless loops caused by inaccurate qlen counters (part 1) There are multiple problems related to qlen adjustment that can lead to an upper qdisc getting out of sync with the real number of packets queued, leading to endless dequeueing attempts by the upper layer code. All qdiscs must maintain an accurate q.qlen counter. There are basically two groups of operations affecting the qlen: operations that propagate down the tree (enqueue, dequeue, requeue, drop, reset) beginning at the root qdisc and operations only affecting a subtree or single qdisc (change, graft, delete class). Since qlen changes during operations from the second group don't propagate to ancestor qdiscs, their qlen values become desynchronized. This patch adds a function to propagate qlen changes up the qdisc tree, optionally calling a callback function to perform qdisc-internal maintenance when the child qdisc becomes empty. The follow-up patches will convert all qdiscs to use this function where necessary. Noticed by Timo Steinbach . Signed-off-by: Patrick McHardy Signed-off-by: David S. Miller --- net/sched/sch_api.c | 38 ++++++++++++++++++++++++++++++++------ 1 file changed, 32 insertions(+), 6 deletions(-) (limited to 'net') diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index d99802f3023d..05a93da6f057 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -191,21 +191,27 @@ int unregister_qdisc(struct Qdisc_ops *qops) (root qdisc, all its children, children of children etc.) */ -struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle) +static struct Qdisc *__qdisc_lookup(struct net_device *dev, u32 handle) { struct Qdisc *q; - read_lock(&qdisc_tree_lock); list_for_each_entry(q, &dev->qdisc_list, list) { - if (q->handle == handle) { - read_unlock(&qdisc_tree_lock); + if (q->handle == handle) return q; - } } - read_unlock(&qdisc_tree_lock); return NULL; } +struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle) +{ + struct Qdisc *q; + + read_lock(&qdisc_tree_lock); + q = __qdisc_lookup(dev, handle); + read_unlock(&qdisc_tree_lock); + return q; +} + static struct Qdisc *qdisc_leaf(struct Qdisc *p, u32 classid) { unsigned long cl; @@ -348,6 +354,26 @@ dev_graft_qdisc(struct net_device *dev, struct Qdisc *qdisc) return oqdisc; } +void qdisc_tree_decrease_qlen(struct Qdisc *sch, unsigned int n) +{ + struct Qdisc_class_ops *cops; + unsigned long cl; + u32 parentid; + + if (n == 0) + return; + while ((parentid = sch->parent)) { + sch = __qdisc_lookup(sch->dev, TC_H_MAJ(parentid)); + cops = sch->ops->cl_ops; + if (cops->qlen_notify) { + cl = cops->get(sch, parentid); + cops->qlen_notify(sch, cl); + cops->put(sch, cl); + } + sch->q.qlen -= n; + } +} +EXPORT_SYMBOL(qdisc_tree_decrease_qlen); /* Graft qdisc "new" to class "classid" of qdisc "parent" or to device "dev". -- cgit v1.2.1