Describe cgroup v2 freezer interface in the cgroup v2 admin guide.
Signed-off-by: Roman Gushchin <g...@fb.com>
Cc: Tejun Heo <t...@kernel.org>
---
Documentation/admin-guide/cgroup-v2.rst | 26 +++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/Documentation/admin-guide/cgroup-v2.rst
b/Documentation/admin-guide/cgroup-v2.rst
index 184193bcb262..a065c0bed88c 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -862,6 +862,8 @@ All cgroup core files are prefixed with "cgroup."
populated
1 if the cgroup or its descendants contains any live
processes; otherwise, 0.
+ frozen
+ 1 if the cgroup is frozen; otherwise, 0.
cgroup.max.descendants
A read-write single value files. The default is "max".
@@ -895,6 +897,30 @@ All cgroup core files are prefixed with "cgroup."
A dying cgroup can consume system resources not exceeding
limits, which were active at the moment of cgroup deletion.
+ cgroup.freeze
+ A read-write single value file which exists on non-root cgroups.
+ Allowed values are "0" and "1". The default is "0".
+
+ Writing "1" to the file causes freezing of the cgroup and all
+ descendant cgroups. This means that all belonging processes will
+ be stopped and will not run until the cgroup will be explicitly
+ unfrozen. Freezing of the cgroup may take some time; when the process
+ is complete, the "frozen" value in the cgroup.events control file
+ will be updated and the corresponding notification will be issued.
+
+ Cgroup can be frozen either by its own settings, either by settings
+ of any ancestor cgroups. If any of ancestor cgroups is frozen, the
+ cgroup will remain frozen.
+
+ Processes in the frozen cgroup can be killed by a fatal signal.
+ They also can enter and leave a frozen cgroup: either by an explicit
+ move by a user, either if freezing of the cgroup races with fork().
+ If a cgroup is moved to a frozen cgroup, it stops. If a process is
+ moving out of a frozen cgroup, it becomes running.
+
+ Frozen status of a cgroup doesn't affect any cgroup tree operations:
+ it's possible to delete a frozen (and empty) cgroup, as well as
+ create new sub-cgroups.
Controllers
===========
--
2.17.2
