cgroup: fix rcu_read_lock() leak in update_if_frozen()

While updating cgroup_freezer locking, 68fafb77d827 ("cgroup_freezer:
replace freezer->lock with freezer_mutex") introduced a bug in
update_if_frozen() where it returns with rcu_read_lock() held.  Fix it
by adding rcu_read_unlock() before returning.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: kbuild test robot <fengguang.wu@intel.com>

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 12ead0b..345628c 100644 (file)
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -267,8 +267,10 @@ static void update_if_frozen(struct cgroup_subsys_state *css)
                struct freezer *child = css_freezer(pos);
 
                if ((child->state & CGROUP_FREEZER_ONLINE) &&
-                   !(child->state & CGROUP_FROZEN))
+                   !(child->state & CGROUP_FROZEN)) {
+                       rcu_read_unlock();
                        return;
+               }
        }
        rcu_read_unlock();