Commit b6053d40 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: fix lockdep warning in debug controller 



The debug controller grabs cgroup_mutex from interface file show
functions which can deadlock and triggers lockdep warnings.  Fix it by
using cgroup_kn_lock_live()/cgroup_kn_unlock() instead.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Waiman Long <longman@redhat.com>
parent 2866c0b4

kernel/cgroup/debug.c

+21 −8
Original line number Diff line number Diff line
@@ -38,12 +38,15 @@ static u64 debug_taskcount_read(struct cgroup_subsys_state *css, 


static int current_css_set_read(struct seq_file *seq, void *v)

{

	struct kernfs_open_file *of = seq->private;

	struct css_set *cset;

	struct cgroup_subsys *ss;

	struct cgroup_subsys_state *css;

	int i, refcnt;



	mutex_lock(&cgroup_mutex);

	if (!cgroup_kn_lock_live(of->kn, false))

		return -ENODEV;



	spin_lock_irq(&css_set_lock);

	rcu_read_lock();

	cset = rcu_dereference(current->cgroups);
@@ -65,7 +68,7 @@ static int current_css_set_read(struct seq_file *seq, void *v) 
	}

	rcu_read_unlock();

	spin_unlock_irq(&css_set_lock);

	mutex_unlock(&cgroup_mutex);

	cgroup_kn_unlock(of->kn);

	return 0;

}
@@ -174,13 +177,17 @@ static int cgroup_css_links_read(struct seq_file *seq, void *v) 


static int cgroup_subsys_states_read(struct seq_file *seq, void *v)

{

	struct cgroup *cgrp = seq_css(seq)->cgroup;

	struct kernfs_open_file *of = seq->private;

	struct cgroup *cgrp;

	struct cgroup_subsys *ss;

	struct cgroup_subsys_state *css;

	char pbuf[16];

	int i;



	mutex_lock(&cgroup_mutex);

	cgrp = cgroup_kn_lock_live(of->kn, false);

	if (!cgrp)

		return -ENODEV;



	for_each_subsys(ss, i) {

		css = rcu_dereference_check(cgrp->subsys[ss->id], true);

		if (!css)
@@ -196,7 +203,8 @@ static int cgroup_subsys_states_read(struct seq_file *seq, void *v) 
			  (unsigned long)css, css->id,

			  atomic_read(&css->online_cnt), pbuf);

	}

	mutex_unlock(&cgroup_mutex);



	cgroup_kn_unlock(of->kn);

	return 0;

}
@@ -221,12 +229,17 @@ static void cgroup_masks_read_one(struct seq_file *seq, const char *name, 


static int cgroup_masks_read(struct seq_file *seq, void *v)

{

	struct cgroup *cgrp = seq_css(seq)->cgroup;

	struct kernfs_open_file *of = seq->private;

	struct cgroup *cgrp;



	cgrp = cgroup_kn_lock_live(of->kn, false);

	if (!cgrp)

		return -ENODEV;



	mutex_lock(&cgroup_mutex);

	cgroup_masks_read_one(seq, "subtree_control", cgrp->subtree_control);

	cgroup_masks_read_one(seq, "subtree_ss_mask", cgrp->subtree_ss_mask);

	mutex_unlock(&cgroup_mutex);



	cgroup_kn_unlock(of->kn);

	return 0;

}