cgroup: add warning about RT not being supported on cgroup2
We haven't yet figured out what to do with RT threads on cgroup2.
Document the limitation.
v2: Included the warning about system management software behavior as
suggested by Michael.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
index 779211f..2cddab7 100644
--- a/Documentation/cgroup-v2.txt
+++ b/Documentation/cgroup-v2.txt
@@ -898,6 +898,13 @@
normal scheduling policy and absolute bandwidth allocation model for
realtime scheduling policy.
+WARNING: cgroup2 doesn't yet support control of realtime processes and
+the cpu controller can only be enabled when all RT processes are in
+the root cgroup. Be aware that system management software may already
+have placed RT processes into nonroot cgroups during the system boot
+process, and these processes may need to be moved to the root cgroup
+before the cpu controller can be enabled.
+
CPU Interface Files
~~~~~~~~~~~~~~~~~~~