From: Tejun Heo <tj@kernel.org>
Date: Tue, 5 Dec 2017 17:10:17 +0000 (-0800)
Subject: cgroup: add warning about RT not being supported on cgroup2
X-Git-Tag: v4.15-rc4~39^2
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=c2f31b79d510ec1a27138bdcf2d0ece1080be85e;p=linux.git

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 779211fbb69f..2cddab7efb20 100644
--- a/Documentation/cgroup-v2.txt
+++ b/Documentation/cgroup-v2.txt
@@ -898,6 +898,13 @@ controller implements weight and absolute bandwidth limit models for
 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
 ~~~~~~~~~~~~~~~~~~~