cgroup: lock cgroup_mutex in cgroup_init_subsys()

Make cgroup_init_subsys() grab cgroup_mutex while initializing a
subsystem so that all helpers and callbacks are called under the
context they expect.  This isn't strictly necessary as
cgroup_init_subsys() doesn't race with anybody but will allow adding
lockdep assertions.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 6cc693b91c4a..09751657abdc 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4317,6 +4317,8 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
 
         printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
 
+        mutex_lock(&cgroup_mutex);
+
         /* init base cftset */
         cgroup_init_cftsets(ss);
 
@@ -4346,6 +4348,8 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
         if (ss->post_create)
                 ss->post_create(dummytop);
 
+        mutex_unlock(&cgroup_mutex);
+
         /* this function shouldn't be used with modular subsystems, since they
          * need to register a subsys_id, among other things */
         BUG_ON(ss->module);