linux/kernel/cgroup_debug.c

/*
 * kernel/ccontainer_debug.c - Example cgroup subsystem that
 * exposes debug info
 *
 * Copyright (C) Google Inc, 2007
 *
 * Developed by Paul Menage (menage@google.com)
 *
 */

#include <linux/cgroup.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/rcupdate.h>

#include <asm/atomic.h>

static struct cgroup_subsys_state *debug_create(struct cgroup_subsys *ss,
						   struct cgroup *cont)
{
	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);

	if (!css)
		return ERR_PTR(-ENOMEM);

	return css;
}

static void debug_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
{
	kfree(cont->subsys[debug_subsys_id]);
}

static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
{
	return atomic_read(&cont->count);
}

static u64 taskcount_read(struct cgroup *cont, struct cftype *cft)
{
	u64 count;

	cgroup_lock();
	count = cgroup_task_count(cont);
	cgroup_unlock();
	return count;
}

static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
{
	return (u64)(long)current->cgroups;
}

static u64 current_css_set_refcount_read(struct cgroup *cont,
					   struct cftype *cft)
{
	u64 count;

	rcu_read_lock();
	count = atomic_read(&current->cgroups->ref.refcount);
	rcu_read_unlock();
	return count;
}

static struct cftype files[] =  {
	{
		.name = "cgroup_refcount",
		.read_uint = cgroup_refcount_read,
	},
	{
		.name = "taskcount",
		.read_uint = taskcount_read,
	},

	{
		.name = "current_css_set",
		.read_uint = current_css_set_read,
	},

	{
		.name = "current_css_set_refcount",
		.read_uint = current_css_set_refcount_read,
	},
};

static int debug_populate(struct cgroup_subsys *ss, struct cgroup *cont)
{
	return cgroup_add_files(cont, ss, files, ARRAY_SIZE(files));
}

struct cgroup_subsys debug_subsys = {
	.name = "debug",
	.create = debug_create,
	.destroy = debug_destroy,
	.populate = debug_populate,
	.subsys_id = debug_subsys_id,
};