Hello, Jiufei. On Fri, Feb 15, 2019 at 02:19:00PM +0800, Jiufei Xue wrote: > The situation can be described as follows. > rmdir umount > cgroup_rmdir > kill_css > css_killed_ref_fn > queue work to destroy css > cgroup_kill_sb > cgroup_put > work performed to destroy css > > Since the percpu_ref of the cgroup_root->cgrp.css hasn't been switched > to atomic mode, cgroup_root can't be destroyed even if not referenced > any more. And it will cause the remount failure in rebind_subsystems() > while remounting different controllers. > > I have no idea how to solve this problem. If we offline the controller > root when there are no alive child, it will trigger the mount hang for > memory controller(commit 3c606d35fe). > > Any ideas? Or should we solve this problem？ Can we just flush the workqueue before trying mount? Thanks. -- tejun
