Describe cgroup v2 freezer interface in the cgroup v2 admin guide. Signed-off-by: Roman Gushchin <guro@xxxxxx> Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Cc: linux-doc@xxxxxxxxxxxxxxx Cc: kernel-team@xxxxxx --- Documentation/admin-guide/cgroup-v2.rst | 27 +++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index 20f92c16ffbf..88e746074252 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -864,6 +864,8 @@ 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". @@ -897,6 +899,31 @@ 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 this action + is completed, the "frozen" value in the cgroup.events control file + will be updated to "1" and the corresponding notification will be + issued. + + A cgroup can be frozen either by its own settings, or 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, or if freezing of the cgroup races with fork(). + If a process is moved to a frozen cgroup, it stops. If a process is + moved 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 =========== -- 2.20.1
