Commit afe471ea authored by Roman Gushchin's avatar Roman Gushchin Committed by Tejun Heo
Browse files

cgroup: document cgroup v2 freezer interface 



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

Signed-off-by: default avatarRoman Gushchin <guro@fb.com>
Reviewed-by: default avatarMike Rapoport <rppt@linux.ibm.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: linux-doc@vger.kernel.org
Cc: kernel-team@fb.com
parent 4c476d8c

Documentation/admin-guide/cgroup-v2.rst

+27 −0
Original line number Original line Diff line number Diff line
@@ -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.





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