2.6.10 vlan stuck on vconfig on interface removal

2.6.10 vlan stuck on vconfig on interface removal

[Andre Tomt]

Hi!

Another "unregister_netdevice: waiting for eth0.1 to become free. Usage 
count = 1" issue coming up.. Fun fun fun! And this one also seems to be 
related to the ipv6 stack.

I can reproduce this reliably this by ifdown lo before ifdown'ing 
eth0.1. That is, if lo goes down first, vconfig rem eth0.1 gets stuck 
when run later. This only happens with ipv6.ko loaded. I havn't added 
*any* ipv6 adresses to any interace, the only one are those the 
ipv6-stack adds itself.

This is hitting us often on our routers, as we have ipv6.ko loaded, and 
Debian runs ifdown -a (bring down all configured interfaces, starting 
with lo unfortunatly) on shutdown and reboot.

Bringing down non-vlan interfaces works just fine after killing lo.

a backtrace from vconfing captured with sysrq-T (quickly typed off-screen):

shedule_timeout
process_timeout
netdev_wait_allrefs
netdev_wait_allrefs
netdev_run_todo
unregister_vlan_device [8021q]
vlan_ioctl_handler [8021q]
sock_ioctl
sys_ioctl
syscall_call

The lab machine is running with a minimalist config, no listeners 
besides sshd, ipv6.ko and 8021q.ko loaded.