Hello,

Does the following patch make the problem go away?

Thank you.

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2097684..f9556cf 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c

@@ -3644,6 +3644,7 @@ static void cgroup_event_remove(struct work_struct *work)

       eventfd_ctx_put(event->eventfd);
       kfree(event);
       dput(cgrp->dentry);
+       deactivate_super(cgrp->root->sb);
 }

 /*

@@ -3770,6 +3771,7 @@ static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,

        * destroying subsystem state objects. Let's take reference to cgroup
        * directory dentry to do that.
        */
+       atomic_inc(&cgrp->root->sb->s_active);
       dget(cgrp->dentry);

       spin_lock(&cgrp->event_list_lock);