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>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 6cc693b91c4a51c32dd636f4685a35c9a395f94e..09751657abdc17f235675c187d925afdd7da9bc2 100644 (file)
--- 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);