If it helps, here's the x-0-greeter.log file while running lightdm v1.2.3-0ubuntu2.5 (when the 100% usage doesn't occur).
** Attachment added: "x-0-greeter1.log" https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1431654/+attachment/4343757/+files/x-0-greeter1.log -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1431654 Title: lightdm (1.2.3-0ubuntu2.6) 100%/high cpu usage To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1431654/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs