Quoting Ryota Ozaki (ozaki.ryota@gmail.com):
I've updated the patch. The change includes support for multiple mount points of cgroups that I didn't cope with in the previous patch.
Through the work, I found a bit messy problem. Current lxc controller writes pid in a 'tasks' file multiple times if one mount point has multiple subsystems. It is bad because the first write changes the cgroups path of a controller, and then the second write points a missing file like $CGROUPS_MOUNTPOINT/<path_to_domain>/<path_to_domain>/tasks where the correct file is $CGROUPS_MOUNTPOINT/<path_to_domain>/tasks. I did workaround this problem with a tricky way by truncating the duplicated path. We probably need a more feasible solution.
Seems like the loop in virCgroupAddTask() should just keep track of which hierarchies it has already written to. Just a small temporary hash table or for that matter a small array that you walk linearly... -serge