Hello!

I'm currently implementing a control group manager that isn't a
persistent daemon.  Instead, it's a command-line tool.  The system
I'm working on uses s6 instead of systemd, and s6 doesn't have native
control group support.

The current plan is to offer a few options:

1. Create a cgroup if it doesn't exist.  If it does, wait for it to
   be empty.  Then execute a program in that cgroup.

2. Create a program in a cgroup, without waiting for the cgroup to
   be empty.

2. Kill all programs in a cgroup.

Unfortunately, I'm not able to wait for a cgroup to become empty.
I don't seem to be getting EPOLLPRI or EPOLLERR events.  What
is the proper way to get those events?  Is there a kernel version
with a bug in this area?
--
Sincerely,
Demi Marie Obenour (she/her/hers)