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SubjectRe: [PATCH v4 7/7] cgroup: document cgroup v2 freezer interface
On Fri, Nov 30, 2018 at 03:47:45PM -0800, Roman Gushchin wrote:
> Describe cgroup v2 freezer interface in the cgroup v2 admin guide.
>
> Signed-off-by: Roman Gushchin <guro@fb.com>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: linux-doc@vger.kernel.org
> Cc: kernel-team@fb.com

Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>

> ---
> 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 07e06136a550..f8335e26b362 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
> ===========
> --
> 2.17.2
>

--
Sincerely yours,
Mike.

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