Linux Ethernet Bridging - Apr 2007 - [Bridge] recent 2.6 kernels hang on bridge shutdown

With recent 2.6 kernels, the command
  brctl delbr br0
hangs during shutdown, and the kernel prints this message again and again:
  unregister_netdevice: waiting for br0 to become free. Usage count = 1

I was able to reproduce this problem with several kernels between 
(and including) 2.6.9-rc1 and 2.6.11-rc2-bk9.
I haven't tried later versions than 2.6.11-rc2-bk9 yet.
2.6.8.1-bk2 still works fine.

My .config was taken from the Debian kernel-image-2.6.10-1-686 package,
adapted to the kernel.org kernels and the processor type set to Pentium
Classic. I can email it on request.

This script should reproduce the problem reliably:
#!/bin/bash
set -x
mount proc -t proc /proc
ifconfig lo 127.0.0.1
brctl addbr br0
modprobe e100   # also works with 3c5x9
brctl addif br0 eth0
ifconfig br0 192.168.1.1
ifconfig eth0 up
sleep 5
ifconfig lo down
lsmod | grep bridge
brctl delif br0 eth0
ifconfig br0 down
brctl delbr br0

To run it, I booted with init=/bin/bash to make sure the distribution's 
startup scripts don't interfere (although it might work anyway).

I already reported this to the linux-kernel list, since I couldn't tell
whether this is a bug in the bridging code or somewhere else.  On second
reading of REPORTING-BUGS, I probably should have sent it here first.

For reference, these are my postings to linux-kernel:
http://www.ussg.iu.edu/hypermail/linux/kernel/0501.3/2222.html
http://www.ussg.iu.edu/hypermail/linux/kernel/0502.0/0139.html

Please let me know if you need any further information,
and please Cc me on replies, since I am not subscribed to the bridge list.

Mirko

On Wed, 2 Feb 2005 18:56:52 +0100
Mirko Parthey <mirko.parthey@informatik.tu-chemnitz.de> wrote:
> With recent 2.6 kernels, the command
>   brctl delbr br0
> hangs during shutdown, and the kernel prints this message again and again:
>   unregister_netdevice: waiting for br0 to become free. Usage count = 1
Are you running IPV6? if so it is most likely related to IPV6.

> I was able to reproduce this problem with several kernels between 
> (and including) 2.6.9-rc1 and 2.6.11-rc2-bk9.
> I haven't tried later versions than 2.6.11-rc2-bk9 yet.
> 2.6.8.1-bk2 still works fine.
> 
> My .config was taken from the Debian kernel-image-2.6.10-1-686 package,
> adapted to the kernel.org kernels and the processor type set to Pentium
> Classic. I can email it on request.
> 
> This script should reproduce the problem reliably:
> #!/bin/bash
> set -x
> mount proc -t proc /proc
> ifconfig lo 127.0.0.1
> brctl addbr br0
> modprobe e100   # also works with 3c5x9
> brctl addif br0 eth0
> ifconfig br0 192.168.1.1
> ifconfig eth0 up
> sleep 5
> ifconfig lo down
> lsmod | grep bridge
> brctl delif br0 eth0
> ifconfig br0 down
> brctl delbr br0
> 
> To run it, I booted with init=/bin/bash to make sure the distribution's
> startup scripts don't interfere (although it might work anyway).
> 
> I already reported this to the linux-kernel list, since I couldn't tell
> whether this is a bug in the bridging code or somewhere else.  On second
> reading of REPORTING-BUGS, I probably should have sent it here first.
> 
> For reference, these are my postings to linux-kernel:
> http://www.ussg.iu.edu/hypermail/linux/kernel/0501.3/2222.html
> http://www.ussg.iu.edu/hypermail/linux/kernel/0502.0/0139.html
> 
> Please let me know if you need any further information,
> and please Cc me on replies, since I am not subscribed to the bridge list.
> 
> Mirko

-- 
Stephen Hemminger	<shemminger@osdl.org>