diff options
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 3a53c771e503..6db8b7f297a1 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4435,7 +4435,15 @@ __setup("cgroup_disable=", cgroup_disable); */ unsigned short css_id(struct cgroup_subsys_state *css) { - struct css_id *cssid = rcu_dereference(css->id); + struct css_id *cssid; + + /* + * This css_id() can return correct value when somone has refcnt + * on this or this is under rcu_read_lock(). Once css->id is allocated, + * it's unchanged until freed. + */ + cssid = rcu_dereference_check(css->id, + rcu_read_lock_held() || atomic_read(&css->refcnt)); if (cssid) return cssid->id; @@ -4445,7 +4453,10 @@ EXPORT_SYMBOL_GPL(css_id); unsigned short css_depth(struct cgroup_subsys_state *css) { - struct css_id *cssid = rcu_dereference(css->id); + struct css_id *cssid; + + cssid = rcu_dereference_check(css->id, + rcu_read_lock_held() || atomic_read(&css->refcnt)); if (cssid) return cssid->depth; |