path: root/kernel/cgroup.c
diff options
authorTejun Heo <>2016-01-21 15:32:15 -0500
committerTejun Heo <>2016-01-22 10:42:58 -0500
commit8bb5ef79bc0f4016ecf79e8dce6096a3c63603e4 (patch)
tree3a2129fd05443c134b033fd476f93ca0faf28b01 /kernel/cgroup.c
parentaa226ff4a1ce79f229c6b7a4c0a14e17fececd01 (diff)
cgroup: make sure a parent css isn't freed before its children
There are three subsystem callbacks in css shutdown path - css_offline(), css_released() and css_free(). Except for css_released(), cgroup core didn't guarantee the order of invocation. css_offline() or css_free() could be called on a parent css before its children. This behavior is unexpected and led to bugs in cpu and memory controller. The previous patch updated ordering for css_offline() which fixes the cpu controller issue. While there currently isn't a known bug caused by misordering of css_free() invocations, let's fix it too for consistency. css_free() ordering can be trivially fixed by moving putting of the parent css below css_free() invocation. Signed-off-by: Tejun Heo <> Cc: Peter Zijlstra <>
Diffstat (limited to 'kernel/cgroup.c')
1 files changed, 4 insertions, 3 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index d01587793865..d27904c193da 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4657,14 +4657,15 @@ static void css_free_work_fn(struct work_struct *work)
if (ss) {
/* css free path */
+ struct cgroup_subsys_state *parent = css->parent;
int id = css->id;
- if (css->parent)
- css_put(css->parent);
cgroup_idr_remove(&ss->css_idr, id);
+ if (parent)
+ css_put(parent);
} else {
/* cgroup free path */