Comment 21 for bug 1196295

This looks to be the third case we hit with the same symptom (and likely for yet another reason). The complicating issue is that lxc containers make use of net namespaces and if those are released, references to I think the netdevice structures, are temporarily moved over to the loopback device. So anything going wrong with respect of references will show up like what you see (to add non mental note: bug 1021471 and bug 1065434).

Since you say it takes 10-15hrs to hit it feels like this could again be a case of something rarely going on when the container is shut down which then causes a reference to not being dropped. Right now the range between 3.5.0-27 (maybe?) and 3.8.0-25 is quite vast. And at least up to 3.10 we can assume it has not been detected/fixed. So unlikely something that will be easy to spot. I know it is a lot of effort, but it would be really important to narrow down the version delta. If possible, I would suggest to use the mainline kernels to start of a rough manual bisection.

http://kernel.ubuntu.com/~kernel-ppa/mainline/