From e67f88dd12f610da98ca838822f2c9b4e7c6100e Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 27 Apr 2011 22:56:07 +0000 Subject: net: dont hold rtnl mutex during netlink dump callbacks Four years ago, Patrick made a change to hold rtnl mutex during netlink dump callbacks. I believe it was a wrong move. This slows down concurrent dumps, making good old /proc/net/ files faster than rtnetlink in some situations. This occurred to me because one "ip link show dev ..." was _very_ slow on a workload adding/removing network devices in background. All dump callbacks are able to use RCU locking now, so this patch does roughly a revert of commits : 1c2d670f366 : [RTNETLINK]: Hold rtnl_mutex during netlink dump callbacks 6313c1e0992 : [RTNETLINK]: Remove unnecessary locking in dump callbacks This let writers fight for rtnl mutex and readers going full speed. It also takes care of phonet : phonet_route_get() is now called from rcu read section. I renamed it to phonet_route_get_rcu() Signed-off-by: Eric Dumazet Cc: Patrick McHardy Cc: Remi Denis-Courmont Acked-by: Stephen Hemminger Signed-off-by: David S. Miller --- net/decnet/dn_dev.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) (limited to 'net/decnet') diff --git a/net/decnet/dn_dev.c b/net/decnet/dn_dev.c index 0dcaa903e00e..404fa1591027 100644 --- a/net/decnet/dn_dev.c +++ b/net/decnet/dn_dev.c @@ -752,7 +752,8 @@ static int dn_nl_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb) skip_naddr = cb->args[1]; idx = 0; - for_each_netdev(&init_net, dev) { + rcu_read_lock(); + for_each_netdev_rcu(&init_net, dev) { if (idx < skip_ndevs) goto cont; else if (idx > skip_ndevs) { @@ -761,11 +762,11 @@ static int dn_nl_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb) skip_naddr = 0; } - if ((dn_db = rtnl_dereference(dev->dn_ptr)) == NULL) + if ((dn_db = rcu_dereference(dev->dn_ptr)) == NULL) goto cont; - for (ifa = rtnl_dereference(dn_db->ifa_list), dn_idx = 0; ifa; - ifa = rtnl_dereference(ifa->ifa_next), dn_idx++) { + for (ifa = rcu_dereference(dn_db->ifa_list), dn_idx = 0; ifa; + ifa = rcu_dereference(ifa->ifa_next), dn_idx++) { if (dn_idx < skip_naddr) continue; @@ -778,6 +779,7 @@ cont: idx++; } done: + rcu_read_unlock(); cb->args[0] = idx; cb->args[1] = dn_idx; -- cgit v1.2.3-59-g8ed1b