24rc8: unregister_netdevice: waiting for ... to become free. Usage count = 1?

24rc8: unregister_netdevice: waiting for ... to become free. Usage count = 1?

[Soeren Sonnenburg]

Dear all,

since some 2.6.24rc version I suddenly experience such messages on
console when trying to shutdown a vpn connection:

unregister_netdevice: waiting for tun0 to become free. Usage count = 1

or when removing an usb wlan dongle (although it was ifconfig wlan0
down'd before)

unregister_netdevice: waiting for wlan0 to become free. Usage count = 1

Then only when all potential connections going over that iface are gone
these messages disappear (sometimes this does not happen and the kernel
then hangs on reboot...)

Is this intended?

Soeren

Re: 24rc8: unregister_netdevice: waiting for ... to become free. Usage count = 1?

[David Miller]

From: Soeren Sonnenburg <kernel@nn7.de>
Date: Wed, 23 Jan 2008 07:42:21 +0100

> Dear all,
> 
> since some 2.6.24rc version I suddenly experience such messages on
> console when trying to shutdown a vpn connection:
> 
> unregister_netdevice: waiting for tun0 to become free. Usage count = 1
> 
> or when removing an usb wlan dongle (although it was ifconfig wlan0
> down'd before)

Current GIT already has a fix for this, attached below:

[NEIGH]: Revert 'Fix race between neigh_parms_release and neightbl_fill_parms'

Commit 9cd40029423701c376391da59d2c6469672b4bed (Fix race between
neigh_parms_release and neightbl_fill_parms) introduced device
reference counting regressions for several people, see:

	http://bugzilla.kernel.org/show_bug.cgi?id=9778

for example.

Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index cc8a2f1..29b8ee4 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1316,6 +1316,8 @@ void neigh_parms_release(struct neigh_table *tbl, struct neigh_parms *parms)
 			*p = parms->next;
 			parms->dead = 1;
 			write_unlock_bh(&tbl->lock);
+			if (parms->dev)
+				dev_put(parms->dev);
 			call_rcu(&parms->rcu_head, neigh_rcu_free_parms);
 			return;
 		}
@@ -1326,8 +1328,6 @@ void neigh_parms_release(struct neigh_table *tbl, struct neigh_parms *parms)
 
 void neigh_parms_destroy(struct neigh_parms *parms)
 {
-	if (parms->dev)
-		dev_put(parms->dev);
 	kfree(parms);
 }
 

Re: 24rc8: unregister_netdevice: waiting for ... to become free. Usage count = 1?

[Soeren Sonnenburg]

On Tue, 2008-01-22 at 22:44 -0800, David Miller wrote:
> From: Soeren Sonnenburg <kernel@nn7.de>
> Date: Wed, 23 Jan 2008 07:42:21 +0100
> 
> > Dear all,
> > 
> > since some 2.6.24rc version I suddenly experience such messages on
> > console when trying to shutdown a vpn connection:
> > 
> > unregister_netdevice: waiting for tun0 to become free. Usage count = 1
> > 
> > or when removing an usb wlan dongle (although it was ifconfig wlan0
> > down'd before)
> 
> Current GIT already has a fix for this, attached below:

Thank you very much for pointing this out!

git pull ; make ; ...
Soeren

Re: 24rc8: unregister_netdevice: waiting for ... to become free. Usage count = 1?

[Soeren Sonnenburg]

On Tue, 2008-01-22 at 22:44 -0800, David Miller wrote:
> From: Soeren Sonnenburg <kernel@nn7.de>
> Date: Wed, 23 Jan 2008 07:42:21 +0100
> 
> > Dear all,
> > 
> > since some 2.6.24rc version I suddenly experience such messages on
> > console when trying to shutdown a vpn connection:
> > 
> > unregister_netdevice: waiting for tun0 to become free. Usage count = 1
> > 
> > or when removing an usb wlan dongle (although it was ifconfig wlan0
> > down'd before)
> 
> Current GIT already has a fix for this, attached below:

hmmhhh, I am still seeing this problem on 2.6.24 with at least with the
madwifi driver...

Soeren