[PATCH] net/dst: dst_dev_event() called after other notifiers

Eric Dumazet
2010-11-09T19:38:02Z

Le lundi 08 novembre 2010 à 16:20 -0800, Ben Greear a écrit :
> This is on an otherwise lightly loaded 2.6.36 + hacks system, 12 physical interfaces,
> and two VETH interfaces.
>
> It's much faster to delete an interface when it has no IPv6 address:
>
> [root@ct503-60 lanforge]# time ip link add link eth5 up name eth5#0 address 00:00:00:00:00:01 type macvlan
>
> real 0m0.005s
> user 0m0.001s
> sys 0m0.004s
> [root@ct503-60 lanforge]# time ip link delete eth5#0
>
> real 0m0.033s
> user 0m0.001s
> sys 0m0.005s
> [root@ct503-60 lanforge]# ip link add link eth5 up name eth5#0 address 00:00:00:00:00:01 type macvlan
>
> [root@ct503-60 lanforge]# ip -6 addr add 2002::1/64 dev eth5#0
> [root@ct503-60 lanforge]# time ip link delete eth5#0
>
> real 0m1.030s
> user 0m0.000s
> sys 0m0.013s
>
>
> Funny enough, if you explicitly remove the IPv6 addr first it seems
> to run at normal speed (adding both operation's times together)
>
> [root@ct503-60 lanforge]# ip link add link eth5 up name eth5#0 address 00:00:00:00:00:01 type macvlan
> [root@ct503-60 lanforge]# ip -6 addr add 2002::1/64 dev eth5#0
> [root@ct503-60 lanforge]# time ip -6 addr delete 2002::1/64 dev eth5#0
>
> real 0m0.001s
> user 0m0.000s
> sys 0m0.001s
> [root@ct503-60 lanforge]# time ip link delete eth5#0
>
> real 0m0.028s
> user 0m0.001s
> sys 0m0.005s
>

OK, I confirm I already knew how to correct the problem.

http://www.spinics.net/lists/netdev/msg140729.html

quote :

I also believe the order of netdevice notifiers is wrong (we dont set
priority), and that we should call fib_netdev_event() _before_
dst_dev_event(). This needs another patch.

Thanks

[PATCH] net/dst: dst_dev_event() called after other notifiers

Followup of commit ef885afbf8a37689 (net: use rcu_barrier() in
rollback_registered_many)

dst_dev_event() scans a garbage dst list that might be feeded by various
network notifiers at device dismantle time.

Its important to call dst_dev_event() after other notifiers, or we might
enter the infamous msleep(250) in netdev_wait_allrefs(), and wait one
second before calling again call_netdevice_notifiers(NETDEV_UNREGISTER,
dev) to properly remove last device references.

Use priority -10 to let dst_dev_notifier be called after other network
notifiers (they have the default 0 priority)

Reported-by: Ben Greear <greearb@candelatech.com>
Reported-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Reported-by: Octavian Purdila <opurdila@ixiacom.com>
Reported-by: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
net/core/dst.c | 1 +
1 files changed, 1 insertion(+)

diff --git a/net/core/dst.c b/net/core/dst.c
index 8abe628..e234bf1 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -370,6 +370,7 @@ static int dst_dev_event(struct notifier_block *this, unsigned long event,

static struct notifier_block dst_dev_notifier = {
.notifier_call = dst_dev_event,
+ .priority = -10, /* must be called after other network notifiers */
};

void __init dst_init(void)