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cgroup: document cgroup v2 freezer interface

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Describe cgroup v2 freezer interface in the cgroup v2 admin guide.

Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: linux-doc@vger.kernel.org
Cc: kernel-team@fb.com
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Roman Gushchin 2019-04-19 10:03:09 -07:00 committed by Tejun Heo
parent 4c476d8cff
commit afe471ea2d
1 changed files with 27 additions and 0 deletions
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Documentation/admin-guide/cgroup-v2.rst
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@ -864,6 +864,8 @@ All cgroup core files are prefixed with "cgroup."
populated populated
1 if the cgroup or its descendants contains any live 1 if the cgroup or its descendants contains any live
processes; otherwise, 0. processes; otherwise, 0.
frozen
1 if the cgroup is frozen; otherwise, 0.
cgroup.max.descendants cgroup.max.descendants
A read-write single value files. The default is "max". 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 A dying cgroup can consume system resources not exceeding
limits, which were active at the moment of cgroup deletion. 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 Controllers
=========== ===========