cgroup: grab cgroup_mutex in drop_parsed_module_refcounts()

This isn't strictly necessary as all subsystems specified in
@subsys_mask are guaranteed to be pinned; however, it does spuriously
trigger lockdep warning.  Let's grab cgroup_mutex around it.

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

1 files changed, 5 insertions, 5 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index e801ecfa36ef..2d3a132e881d 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1325,11 +1325,11 @@ static void drop_parsed_module_refcounts(unsigned long subsys_mask)
         struct cgroup_subsys *ss;
         int i;
 
-        for_each_subsys(ss, i) {
-                if (!(subsys_mask & (1UL << i)))
-                        continue;
-                module_put(cgroup_subsys[i]->module);
-        }
+        mutex_lock(&cgroup_mutex);
+        for_each_subsys(ss, i)
+                if (subsys_mask & (1UL << i))
+                        module_put(cgroup_subsys[i]->module);
+        mutex_unlock(&cgroup_mutex);
 }
 
 static int cgroup_remount(struct super_block *sb, int *flags, char *data)