Implementing a control group manager that isn't a persistent daemon

Demi Marie Obenour <[email protected]> Sun, 12 Jul 2026 18:50:57 -0400

Newsgroups	org.kernel.vger.cgroups
Message-ID	<[email protected]>

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)

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