cgroup: make css_sets pin the associated cgroups
authorTejun Heo <tj@kernel.org>
Thu, 15 Oct 2015 20:41:51 +0000 (16:41 -0400)
committerTejun Heo <tj@kernel.org>
Thu, 15 Oct 2015 20:41:51 +0000 (16:41 -0400)
commit2ceb231b0ab0e3d700c5f7c839273bfeecbefe3b
tree8bd0339acd6735a8733f37f0f81d6b950d735c3a
parent052c3f3a0b03651d94050d917ebc1df46a31c2f0
cgroup: make css_sets pin the associated cgroups

Currently, css_sets don't pin the associated cgroups.  This is okay as
a cgroup with css_sets associated are not allowed to be removed;
however, to help resource tracking for zombie tasks, this is scheduled
to change such that a cgroup can be removed even when it has css_sets
associated as long as none of them are populated.

To ensure that a cgroup doesn't go away while css_sets are still
associated with it, make each associated css_set hold a reference on
the cgroup if non-root.

v2: Root cgroups are special and shouldn't be ref'd by css_sets.

Signed-off-by: Tejun Heo <tj@kernel.org>
kernel/cgroup.c