/sbin/cgmanager --sigstop -m name=systemd stuck for several hours using 100% CPU

I left my notebook running over night, and when I checked in the morning I found:

  PID USER PR NI VIRT RES SHR SWAP S %CPU %MEM TIME+ COMMAND
 5902 root 20 0 35.1m 12.0m 1.1m 1.3m R 97.7 0.2 974:53.44 /sbin/cgmanager --sigstop -m name=systemd

which now (several hours later) still didn't stop

A backtrace from attaching to the process gives:
(gdb) bt full
#0 _dbus_connection_update_dispatch_status_and_unlock (connection=0x7f589ecb2ca0, new_status=DBUS_DISPATCH_COMPLETE) at ../../dbus/dbus-connection.c:4255
        changed = <optimized out>
        function = <optimized out>
        data = <optimized out>
#1 0x00007f589c0e0792 in dbus_connection_dispatch (connection=0x7f589ecb2ca0) at ../../dbus/dbus-connection.c:4522
        message = <optimized out>
        link = <optimized out>
        filter_list_copy = 0x7fffa9045710
        message_link = <optimized out>
        result = <optimized out>
        pending = <optimized out>
        reply_serial = <optimized out>
        status = DBUS_DISPATCH_COMPLETE
        found_object = 32767
        __FUNCTION__ = "dbus_connection_dispatch"
#2 0x00007f589c31a418 in ?? () from /lib/x86_64-linux-gnu/libnih-dbus.so.1
No symbol table info available.
#3 0x00007f589c52e2ba in nih_main_loop () from /lib/x86_64-linux-gnu/libnih.so.1
No symbol table info available.
#4 0x00007f589c962639 in ?? ()
No symbol table info available.
#5 0x00007f589bd2dec5 in __libc_start_main (main=0x7f589c962410, argc=4, argv=0x7fffa90459e8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffa90459d8) at libc-start.c:287
        result = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {0, 3885596728707560085, 140018560935990, 140736029022688, 0, 0, -3885696444087618923, -3792771927287614827}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0,
              0x7fffa9045a10, 0x7f589c95d1c8}, data = {prev = 0x0, cleanup = 0x0, canceltype = -1459332592}}}
        not_first_call = <optimized out>
#6 0x00007f589c96285f in ?? ()
No symbol table info available.

(gdb) bt
#0 0x00007f589bdfec13 in __select_nocancel () at ../sysdeps/unix/syscall-template.S:81
#1 0x00007f589c52e239 in nih_main_loop () from /lib/x86_64-linux-gnu/libnih.so.1
#2 0x00007f589c962639 in ?? ()
#3 0x00007f589bd2dec5 in __libc_start_main (main=0x7f589c962410, argc=4, argv=0x7fffa90459e8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffa90459d8) at libc-start.c:287
#4 0x00007f589c96285f in ?? ()

and others, but nih appears in every trace and dbus in most

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: cgmanager 0.24-0ubuntu4
ProcVersionSignature: Ubuntu 3.13.0-21.43-generic 3.13.8
Uname: Linux 3.13.0-21-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.14.1-0ubuntu2
Architecture: amd64
Date: Tue Apr 15 19:32:35 2014
EcryptfsInUse: Yes
ExecutablePath: /sbin/cgmanager
InstallationDate: Installed on 2011-10-08 (920 days ago)
InstallationMedia: Kubuntu 11.10 "Oneiric Ocelot" - Beta amd64 (20111007)
ProcEnviron:
 TERM=linux
 PATH=(custom, no user)
SourcePackage: cgmanager
UpgradeStatus: No upgrade log present (probably fresh install)