net_sched: transform qdisc running bit into a seqcount
Instead of using a single bit (__QDISC___STATE_RUNNING)
in sch->__state, use a seqcount.
This adds lockdep support, but more importantly it will allow us
to sample qdisc/class statistics without having to grab qdisc root lock.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.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 269dd71..cebea73 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -110,7 +110,7 @@
/*
* Transmit possibly several skbs, and handle the return status as
- * required. Holding the __QDISC___STATE_RUNNING bit guarantees that
+ * required. Owning running seqcount bit guarantees that
* only one CPU can execute this function.
*
* Returns to the caller:
@@ -137,10 +137,10 @@
HARD_TX_UNLOCK(dev, txq);
} else {
- spin_lock(root_lock);
+ spin_lock_nested(root_lock, SINGLE_DEPTH_NESTING);
return qdisc_qlen(q);
}
- spin_lock(root_lock);
+ spin_lock_nested(root_lock, SINGLE_DEPTH_NESTING);
if (dev_xmit_complete(ret)) {
/* Driver sent out skb successfully or skb was consumed */
@@ -163,7 +163,7 @@
/*
* NOTE: Called under qdisc_lock(q) with locally disabled BH.
*
- * __QDISC___STATE_RUNNING guarantees only one CPU can process
+ * running seqcount guarantees only one CPU can process
* this qdisc at a time. qdisc_lock(q) serializes queue accesses for
* this queue.
*
@@ -379,6 +379,7 @@
.list = LIST_HEAD_INIT(noop_qdisc.list),
.q.lock = __SPIN_LOCK_UNLOCKED(noop_qdisc.q.lock),
.dev_queue = &noop_netdev_queue,
+ .running = SEQCNT_ZERO(noop_qdisc.running),
.busylock = __SPIN_LOCK_UNLOCKED(noop_qdisc.busylock),
};
EXPORT_SYMBOL(noop_qdisc);
@@ -537,6 +538,7 @@
EXPORT_SYMBOL(pfifo_fast_ops);
static struct lock_class_key qdisc_tx_busylock;
+static struct lock_class_key qdisc_running_key;
struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
const struct Qdisc_ops *ops)
@@ -570,6 +572,10 @@
lockdep_set_class(&sch->busylock,
dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);
+ seqcount_init(&sch->running);
+ lockdep_set_class(&sch->running,
+ dev->qdisc_running_key ?: &qdisc_running_key);
+
sch->ops = ops;
sch->enqueue = ops->enqueue;
sch->dequeue = ops->dequeue;