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cgroup: fix lockdep warning in debug controller

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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: Tejun Heo <tj@kernel.org>
Cc: Waiman Long <longman@redhat.com>
This commit is contained in:
Tejun Heo 2017-06-14 16:01:41 -04:00
parent 2866c0b4cf
commit b6053d40e3
1 changed files with 21 additions and 8 deletions
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29
kernel/cgroup/debug.c
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@ -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;
}