Commits
Tejun Heo committed 8353da1f91f
cgroup: remove cgroup_tree_mutex cgroup_tree_mutex was introduced to work around the circular dependency between cgroup_mutex and kernfs active protection - some kernfs file and directory operations needed cgroup_mutex putting cgroup_mutex under active protection but cgroup also needs to be able to access cgroup hierarchies and cftypes to determine which kernfs_nodes need to be removed. cgroup_tree_mutex nested above both cgroup_mutex and kernfs active protection and used to protect the hierarchy and cftypes. While this worked, it added a lot of double lockings and was generally cumbersome. kernfs provides a mechanism to opt out of active protection and cgroup was already using it for removal and subtree_control. There's no reason to mix both methods of avoiding circular locking dependency and the preceding cgroup_kn_lock_live() changes applied it to all relevant cgroup kernfs operations making it unnecessary to nest cgroup_mutex under kernfs active protection. The previous patch reversed the original lock ordering and put cgroup_mutex above kernfs active protection. After these changes, all cgroup_tree_mutex usages are now accompanied by cgroup_mutex making the former completely redundant. This patch removes cgroup_tree_mutex and all its usages. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>