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Date: Fri, 22 Aug 2008 08:41:50 +0000
From: Jarek Poplawski <jarkao2@...il.com>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
denys@...p.net.lb
Subject: [PATCH] pkt_sched: Fix qdisc list locking
On Fri, Aug 22, 2008 at 08:24:47AM +1000, Herbert Xu wrote:
...
> Feel free to fix this up into a real patch with a new lock.
It looks like adding to the list needs similar protection, but if I
exagerated here let me know.
Thanks,
Jarek P.
--------------->
pkt_sched: Fix qdisc list locking
Since some qdiscs call qdisc_tree_decrease_qlen() (so qdisc_lookup())
without rtnl_lock(), adding and deleting from a qdisc list needs
additional locking. This patch adds global spinlock qdisc_list_lock
and wrapper functions for modifying the list. It is considered as a
temporary solution until hfsc_dequeue(), netem_dequeue() and
tbf_dequeue() (or qdisc_tree_decrease_qlen()) are redone.
With feedback from Herbert Xu and David S. Miller.
Signed-off-by: Jarek Poplawski <jarkao2@...il.com>
---
include/net/pkt_sched.h | 1 +
net/sched/sch_api.c | 44 +++++++++++++++++++++++++++++++++++++++-----
net/sched/sch_generic.c | 5 ++---
3 files changed, 42 insertions(+), 8 deletions(-)
diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index 853fe83..b786a5b 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -78,6 +78,7 @@ extern struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
extern int register_qdisc(struct Qdisc_ops *qops);
extern int unregister_qdisc(struct Qdisc_ops *qops);
+extern void qdisc_list_del(struct Qdisc *q);
extern struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle);
extern struct Qdisc *qdisc_lookup_class(struct net_device *dev, u32 handle);
extern struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r,
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 45f442d..e35b8d8 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -199,19 +199,53 @@ struct Qdisc *qdisc_match_from_root(struct Qdisc *root, u32 handle)
return NULL;
}
+/*
+ * This lock is needed until some qdiscs stop calling qdisc_tree_decrease_qlen()
+ * without rtnl_lock(); currently hfsc_dequeue(), netem_dequeue(), tbf_dequeue()
+ */
+static DEFINE_SPINLOCK(qdisc_lookup_lock);
+
+static void qdisc_list_add(struct Qdisc *q)
+{
+ if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS)) {
+ spin_lock_bh(&qdisc_lookup_lock);
+ list_add_tail(&q->list, &qdisc_root_sleeping(q)->list);
+ spin_unlock_bh(&qdisc_lookup_lock);
+ }
+}
+
+void qdisc_list_del(struct Qdisc *q)
+{
+ if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS)) {
+ spin_lock_bh(&qdisc_lookup_lock);
+ list_del(&q->list);
+ spin_unlock_bh(&qdisc_lookup_lock);
+ }
+}
+EXPORT_SYMBOL(qdisc_list_del);
+
struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle)
{
unsigned int i;
+ struct Qdisc *q;
+
+ spin_lock_bh(&qdisc_lookup_lock);
for (i = 0; i < dev->num_tx_queues; i++) {
struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
- struct Qdisc *q, *txq_root = txq->qdisc_sleeping;
+ struct Qdisc *txq_root = txq->qdisc_sleeping;
q = qdisc_match_from_root(txq_root, handle);
if (q)
- return q;
+ goto unlock;
}
- return qdisc_match_from_root(dev->rx_queue.qdisc_sleeping, handle);
+
+ q = qdisc_match_from_root(dev->rx_queue.qdisc_sleeping, handle);
+
+unlock:
+ spin_unlock_bh(&qdisc_lookup_lock);
+
+ return q;
}
static struct Qdisc *qdisc_leaf(struct Qdisc *p, u32 classid)
@@ -810,8 +844,8 @@ qdisc_create(struct net_device *dev, struct netdev_queue *dev_queue,
goto err_out3;
}
}
- if ((parent != TC_H_ROOT) && !(sch->flags & TCQ_F_INGRESS))
- list_add_tail(&sch->list, &dev_queue->qdisc_sleeping->list);
+
+ qdisc_list_add(sch);
return sch;
}
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index c3ed4d4..5f0ade7 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -526,10 +526,9 @@ void qdisc_destroy(struct Qdisc *qdisc)
!atomic_dec_and_test(&qdisc->refcnt))
return;
- if (qdisc->parent)
- list_del(&qdisc->list);
-
#ifdef CONFIG_NET_SCHED
+ qdisc_list_del(qdisc);
+
qdisc_put_stab(qdisc->stab);
#endif
gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);
--
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