Commit bb758421 authored by Shakeel Butt's avatar Shakeel Butt Committed by Tejun Heo
Browse files

cgroup: remove cgroup_mutex from cgroupstats_build 



The function cgroupstats_build extracts cgroup from the kernfs_node's
priv pointer which is a RCU pointer. So, there is no need to grab
cgroup_mutex. Just get the reference on the cgroup before using and
remove the cgroup_mutex altogether.

Signed-off-by: default avatarShakeel Butt <shakeelb@google.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent be288169

kernel/cgroup/cgroup-v1.c

+2 −5
Original line number Diff line number Diff line
@@ -698,8 +698,6 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) 
	    kernfs_type(kn) != KERNFS_DIR)

		return -EINVAL;



	mutex_lock(&cgroup_mutex);



	/*

	 * We aren't being called from kernfs and there's no guarantee on

	 * @kn->priv's validity.  For this and css_tryget_online_from_dir(),
@@ -707,9 +705,8 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) 
	 */

	rcu_read_lock();

	cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);

	if (!cgrp || cgroup_is_dead(cgrp)) {

	if (!cgrp || !cgroup_tryget(cgrp)) {

		rcu_read_unlock();

		mutex_unlock(&cgroup_mutex);

		return -ENOENT;

	}

	rcu_read_unlock();
@@ -737,7 +734,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) 
	}

	css_task_iter_end(&it);



	mutex_unlock(&cgroup_mutex);

	cgroup_put(cgrp);

	return 0;

}