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

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Message-ID: <1289331475.2774.41.camel@edumazet-laptop>
Date:	Tue, 09 Nov 2010 20:37:55 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ben Greear <greearb@...delatech.com>,
	David Miller <davem@...emloft.net>
Cc:	NetDev <netdev@...r.kernel.org>
Subject: [PATCH] net/dst: dst_dev_event() called after other notifiers

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@...03-60 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@...03-60 lanforge]# time ip link delete eth5#0
> 
> real	0m0.033s
> user	0m0.001s
> sys	0m0.005s
> [root@...03-60 lanforge]# ip link add link eth5 up name eth5#0 address 00:00:00:00:00:01 type macvlan
> 
> [root@...03-60 lanforge]# ip -6 addr add 2002::1/64 dev eth5#0
> [root@...03-60 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@...03-60 lanforge]# ip link add link eth5 up name eth5#0 address 00:00:00:00:00:01 type macvlan
> [root@...03-60 lanforge]# ip -6 addr add 2002::1/64 dev eth5#0
> [root@...03-60 lanforge]# time ip -6 addr delete 2002::1/64 dev eth5#0
> 
> real	0m0.001s
> user	0m0.000s
> sys	0m0.001s
> [root@...03-60 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@...delatech.com>
Reported-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>
Reported-by: Octavian Purdila <opurdila@...acom.com>
Reported-by: Benjamin LaHaise <bcrl@...ck.org>
Signed-off-by: Eric Dumazet <eric.dumazet@...il.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)


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