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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2011-04-27 22:56:07 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2011-05-02 15:26:28 -0700 |
| commit | e67f88dd12f610da98ca838822f2c9b4e7c6100e (patch) | |
| tree | 6cf01b794984aaad97b6e6ff6e5103bc48d68191 /net/decnet | |
| parent | dcfd9cdc1222f14d6180514e533289493a0716fb (diff) | |
| download | lwn-e67f88dd12f610da98ca838822f2c9b4e7c6100e.tar.gz lwn-e67f88dd12f610da98ca838822f2c9b4e7c6100e.zip | |
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 <eric.dumazet@gmail.com>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Remi Denis-Courmont <remi.denis-courmont@nokia.com>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/decnet')
| -rw-r--r-- | net/decnet/dn_dev.c | 10 |
1 files changed, 6 insertions, 4 deletions
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; |