1 files changed, 16 insertions, 3 deletions

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 7fa476f01d05..fb249e2bcada 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -184,9 +184,20 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
 {
         struct freezer *freezer;
 
-        task_lock(task);
+        /*
+         * No lock is needed, since the task isn't on tasklist yet,
+         * so it can't be moved to another cgroup, which means the
+         * freezer won't be removed and will be valid during this
+         * function call.
+         */
         freezer = task_freezer(task);
-        task_unlock(task);
+
+        /*
+         * The root cgroup is non-freezable, so we can skip the
+         * following check.
+         */
+        if (!freezer->css.cgroup->parent)
+                return;
 
         spin_lock_irq(&freezer->lock);
         BUG_ON(freezer->state == CGROUP_FROZEN);
@@ -331,7 +342,7 @@ static int freezer_write(struct cgroup *cgroup,
         else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0)
                 goal_state = CGROUP_FROZEN;
         else
-                return -EIO;
+                return -EINVAL;
 
         if (!cgroup_lock_live_group(cgroup))
                 return -ENODEV;
@@ -350,6 +361,8 @@ static struct cftype files[] = {
 
 static int freezer_populate(struct cgroup_subsys *ss, struct cgroup *cgroup)
 {
+        if (!cgroup->parent)
+                return 0;
         return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files));
 }