netdev - [PATCH net-next 1/2] pkt_sched: do not use rcu in tc_dump

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Date:	Mon, 10 Mar 2014 17:11:42 -0700
From:	Eric Dumazet <edumazet@...gle.com>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 1/2] pkt_sched: do not use rcu in tc_dump_qdisc()

Like all rtnetlink dump operations, we hold RTNL in tc_dump_qdisc(),
so we do not need to use rcu protection to protect list of netdevices.

This will allow preemption to occur, thus reducing latencies.
Following patch adds explicit cond_resched() calls.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/sched/sch_api.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 1313145e3b86..272292efa7f0 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1434,9 +1434,9 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
 	s_idx = cb->args[0];
 	s_q_idx = q_idx = cb->args[1];

-	rcu_read_lock();
 	idx = 0;
-	for_each_netdev_rcu(net, dev) {
+	ASSERT_RTNL();
+	for_each_netdev(net, dev) {
 		struct netdev_queue *dev_queue;

 		if (idx < s_idx)
@@ -1459,8 +1459,6 @@ cont:
 	}

 done:
-	rcu_read_unlock();
-
 	cb->args[0] = idx;
 	cb->args[1] = q_idx;

-- 
1.9.0.279.gdc9e3eb

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