[GitHub/LineageOS/android_kernel_samsung_universal7580.git] / kernel / cgroup_freezer.c

/*
 * cgroup_freezer.c -  control group freezer subsystem
 *
 * Copyright IBM Corporation, 2007
 *
 * Author : Cedric Le Goater <clg@fr.ibm.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2.1 of the GNU Lesser General Public License
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 */

#include <linux/export.h>
#include <linux/slab.h>
#include <linux/cgroup.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/freezer.h>
#include <linux/seq_file.h>

enum freezer_state {
	CGROUP_THAWED = 0,
	CGROUP_FREEZING,
	CGROUP_FROZEN,
};

struct freezer {
	struct cgroup_subsys_state css;
	enum freezer_state state;
	spinlock_t lock; /* protects _writes_ to state */
};

static inline struct freezer *cgroup_freezer(
		struct cgroup *cgroup)
{
	return container_of(
		cgroup_subsys_state(cgroup, freezer_subsys_id),
		struct freezer, css);
}

static inline struct freezer *task_freezer(struct task_struct *task)
{
	return container_of(task_subsys_state(task, freezer_subsys_id),
			    struct freezer, css);
}

bool cgroup_freezing(struct task_struct *task)
{
	enum freezer_state state;
	bool ret;

	rcu_read_lock();
	state = task_freezer(task)->state;
	ret = state == CGROUP_FREEZING || state == CGROUP_FROZEN;
	rcu_read_unlock();

	return ret;
}

/*
 * cgroups_write_string() limits the size of freezer state strings to
 * CGROUP_LOCAL_BUFFER_SIZE
 */
static const char *freezer_state_strs[] = {
	"THAWED",
	"FREEZING",
	"FROZEN",
};

/*
 * State diagram
 * Transitions are caused by userspace writes to the freezer.state file.
 * The values in parenthesis are state labels. The rest are edge labels.
 *
 * (THAWED) --FROZEN--> (FREEZING) --FROZEN--> (FROZEN)
 *    ^ ^                    |                     |
 *    | \_______THAWED_______/                     |
 *    \__________________________THAWED____________/
 */

struct cgroup_subsys freezer_subsys;

/* Locks taken and their ordering
 * ------------------------------
 * cgroup_mutex (AKA cgroup_lock)
 * freezer->lock
 * css_set_lock
 * task->alloc_lock (AKA task_lock)
 * task->sighand->siglock
 *
 * cgroup code forces css_set_lock to be taken before task->alloc_lock
 *
 * freezer_create(), freezer_destroy():
 * cgroup_mutex [ by cgroup core ]
 *
 * freezer_can_attach():
 * cgroup_mutex (held by caller of can_attach)
 *
 * freezer_fork() (preserving fork() performance means can't take cgroup_mutex):
 * freezer->lock
 *  sighand->siglock (if the cgroup is freezing)
 *
 * freezer_read():
 * cgroup_mutex
 *  freezer->lock
 *   write_lock css_set_lock (cgroup iterator start)
 *    task->alloc_lock
 *   read_lock css_set_lock (cgroup iterator start)
 *
 * freezer_write() (freeze):
 * cgroup_mutex
 *  freezer->lock
 *   write_lock css_set_lock (cgroup iterator start)
 *    task->alloc_lock
 *   read_lock css_set_lock (cgroup iterator start)
 *    sighand->siglock (fake signal delivery inside freeze_task())
 *
 * freezer_write() (unfreeze):
 * cgroup_mutex
 *  freezer->lock
 *   write_lock css_set_lock (cgroup iterator start)
 *    task->alloc_lock
 *   read_lock css_set_lock (cgroup iterator start)
 *    task->alloc_lock (inside __thaw_task(), prevents race with refrigerator())
 *     sighand->siglock
 */
static struct cgroup_subsys_state *freezer_create(struct cgroup_subsys *ss,
						  struct cgroup *cgroup)
{
	struct freezer *freezer;

	freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL);
	if (!freezer)
		return ERR_PTR(-ENOMEM);

	spin_lock_init(&freezer->lock);
	freezer->state = CGROUP_THAWED;
	return &freezer->css;
}

static void freezer_destroy(struct cgroup_subsys *ss,
			    struct cgroup *cgroup)
{
	struct freezer *freezer = cgroup_freezer(cgroup);

	if (freezer->state != CGROUP_THAWED)
		atomic_dec(&system_freezing_cnt);
	kfree(freezer);
}

/* task is frozen or will freeze immediately when next it gets woken */
static bool is_task_frozen_enough(struct task_struct *task)
{
	return frozen(task) ||
		(task_is_stopped_or_traced(task) && freezing(task));
}

/*
 * The call to cgroup_lock() in the freezer.state write method prevents
 * a write to that file racing against an attach, and hence the
 * can_attach() result will remain valid until the attach completes.
 */
static int freezer_can_attach(struct cgroup_subsys *ss,
			      struct cgroup *new_cgroup,
			      struct cgroup_taskset *tset)
{
	struct freezer *freezer;
	struct task_struct *task;

	/*
	 * Anything frozen can't move or be moved to/from.
	 */
	cgroup_taskset_for_each(task, new_cgroup, tset)
		if (cgroup_freezing(task))
			return -EBUSY;

	freezer = cgroup_freezer(new_cgroup);
	if (freezer->state != CGROUP_THAWED)
		return -EBUSY;

	return 0;
}

static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
{
	struct freezer *freezer;

	/*
	 * No lock is needed, since the task isn't on tasklist yet,
	 * so it can't be moved to another cgroup, which means the
	 * freezer won't be removed and will be valid during this
	 * function call.  Nevertheless, apply RCU read-side critical
	 * section to suppress RCU lockdep false positives.
	 */
	rcu_read_lock();
	freezer = task_freezer(task);
	rcu_read_unlock();

	/*
	 * The root cgroup is non-freezable, so we can skip the
	 * following check.
	 */
	if (!freezer->css.cgroup->parent)
		return;

	spin_lock_irq(&freezer->lock);
	BUG_ON(freezer->state == CGROUP_FROZEN);

	/* Locking avoids race with FREEZING -> THAWED transitions. */
	if (freezer->state == CGROUP_FREEZING)
		freeze_task(task);
	spin_unlock_irq(&freezer->lock);
}

/*
 * caller must hold freezer->lock
 */
static void update_if_frozen(struct cgroup *cgroup,
				 struct freezer *freezer)
{
	struct cgroup_iter it;
	struct task_struct *task;
	unsigned int nfrozen = 0, ntotal = 0;
	enum freezer_state old_state = freezer->state;

	cgroup_iter_start(cgroup, &it);
	while ((task = cgroup_iter_next(cgroup, &it))) {
		ntotal++;
		if (freezing(task) && is_task_frozen_enough(task))
			nfrozen++;
	}

	if (old_state == CGROUP_THAWED) {
		BUG_ON(nfrozen > 0);
	} else if (old_state == CGROUP_FREEZING) {
		if (nfrozen == ntotal)
			freezer->state = CGROUP_FROZEN;
	} else { /* old_state == CGROUP_FROZEN */
		BUG_ON(nfrozen != ntotal);
	}

	cgroup_iter_end(cgroup, &it);
}

static int freezer_read(struct cgroup *cgroup, struct cftype *cft,
			struct seq_file *m)
{
	struct freezer *freezer;
	enum freezer_state state;

	if (!cgroup_lock_live_group(cgroup))
		return -ENODEV;

	freezer = cgroup_freezer(cgroup);
	spin_lock_irq(&freezer->lock);
	state = freezer->state;
	if (state == CGROUP_FREEZING) {
		/* We change from FREEZING to FROZEN lazily if the cgroup was
		 * only partially frozen when we exitted write. */
		update_if_frozen(cgroup, freezer);
		state = freezer->state;
	}
	spin_unlock_irq(&freezer->lock);
	cgroup_unlock();

	seq_puts(m, freezer_state_strs[state]);
	seq_putc(m, '\n');
	return 0;
}

static int try_to_freeze_cgroup(struct cgroup *cgroup, struct freezer *freezer)
{
	struct cgroup_iter it;
	struct task_struct *task;
	unsigned int num_cant_freeze_now = 0;

	cgroup_iter_start(cgroup, &it);
	while ((task = cgroup_iter_next(cgroup, &it))) {
		if (!freeze_task(task))
			continue;
		if (is_task_frozen_enough(task))
			continue;
		if (!freezing(task) && !freezer_should_skip(task))
			num_cant_freeze_now++;
	}
	cgroup_iter_end(cgroup, &it);

	return num_cant_freeze_now ? -EBUSY : 0;
}

static void unfreeze_cgroup(struct cgroup *cgroup, struct freezer *freezer)
{
	struct cgroup_iter it;
	struct task_struct *task;

	cgroup_iter_start(cgroup, &it);
	while ((task = cgroup_iter_next(cgroup, &it)))
		__thaw_task(task);
	cgroup_iter_end(cgroup, &it);
}

static int freezer_change_state(struct cgroup *cgroup,
				enum freezer_state goal_state)
{
	struct freezer *freezer;
	int retval = 0;

	freezer = cgroup_freezer(cgroup);

	spin_lock_irq(&freezer->lock);

	update_if_frozen(cgroup, freezer);

	switch (goal_state) {
	case CGROUP_THAWED:
		if (freezer->state != CGROUP_THAWED)
			atomic_dec(&system_freezing_cnt);
		freezer->state = CGROUP_THAWED;
		unfreeze_cgroup(cgroup, freezer);
		break;
	case CGROUP_FROZEN:
		if (freezer->state == CGROUP_THAWED)
			atomic_inc(&system_freezing_cnt);
		freezer->state = CGROUP_FREEZING;
		retval = try_to_freeze_cgroup(cgroup, freezer);
		break;
	default:
		BUG();
	}

	spin_unlock_irq(&freezer->lock);

	return retval;
}

static int freezer_write(struct cgroup *cgroup,
			 struct cftype *cft,
			 const char *buffer)
{
	int retval;
	enum freezer_state goal_state;

	if (strcmp(buffer, freezer_state_strs[CGROUP_THAWED]) == 0)
		goal_state = CGROUP_THAWED;
	else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0)
		goal_state = CGROUP_FROZEN;
	else
		return -EINVAL;

	if (!cgroup_lock_live_group(cgroup))
		return -ENODEV;
	retval = freezer_change_state(cgroup, goal_state);
	cgroup_unlock();
	return retval;
}

static struct cftype files[] = {
	{
		.name = "state",
		.read_seq_string = freezer_read,
		.write_string = freezer_write,
	},
};

static int freezer_populate(struct cgroup_subsys *ss, struct cgroup *cgroup)
{
	if (!cgroup->parent)
		return 0;
	return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files));
}

struct cgroup_subsys freezer_subsys = {
	.name		= "freezer",
	.create		= freezer_create,
	.destroy	= freezer_destroy,
	.populate	= freezer_populate,
	.subsys_id	= freezer_subsys_id,
	.can_attach	= freezer_can_attach,
	.fork		= freezer_fork,
};
Commit	Line	Data
dc52ddc0 MH	1	/*
	2	* cgroup_freezer.c - control group freezer subsystem
	3	*
	4	* Copyright IBM Corporation, 2007
	5	*
	6	* Author : Cedric Le Goater <clg@fr.ibm.com>
	7	*
	8	* This program is free software; you can redistribute it and/or modify it
	9	* under the terms of version 2.1 of the GNU Lesser General Public License
	10	* as published by the Free Software Foundation.
	11	*
	12	* This program is distributed in the hope that it would be useful, but
	13	* WITHOUT ANY WARRANTY; without even the implied warranty of
	14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
	15	*/
	16
9984de1a	17	#include <linux/export.h>
5a0e3ad6	18	#include <linux/slab.h>
dc52ddc0 MH	19	#include <linux/cgroup.h>
	20	#include <linux/fs.h>
	21	#include <linux/uaccess.h>
	22	#include <linux/freezer.h>
	23	#include <linux/seq_file.h>
	24
	25	enum freezer_state {
81dcf33c MH	26	CGROUP_THAWED = 0,
	27	CGROUP_FREEZING,
	28	CGROUP_FROZEN,
dc52ddc0 MH	29	};
	30
	31	struct freezer {
	32	struct cgroup_subsys_state css;
	33	enum freezer_state state;
	34	spinlock_t lock; /* protects _writes_ to state */
	35	};
	36
	37	static inline struct freezer *cgroup_freezer(
	38	struct cgroup *cgroup)
	39	{
	40	return container_of(
	41	cgroup_subsys_state(cgroup, freezer_subsys_id),
	42	struct freezer, css);
	43	}
	44
	45	static inline struct freezer task_freezer(struct task_struct task)
	46	{
	47	return container_of(task_subsys_state(task, freezer_subsys_id),
	48	struct freezer, css);
	49	}
	50
22b4e111	51	bool cgroup_freezing(struct task_struct *task)
dc52ddc0	52	{
22b4e111 TH	53	enum freezer_state state;
22b4e111 TH	54	bool ret;
dc52ddc0	55
22b4e111 TH	56	rcu_read_lock();
	57	state = task_freezer(task)->state;
	58	ret = state == CGROUP_FREEZING \|\| state == CGROUP_FROZEN;
	59	rcu_read_unlock();
	60
	61	return ret;
dc52ddc0 MH	62	}
	63
	64	/*
	65	* cgroups_write_string() limits the size of freezer state strings to
	66	* CGROUP_LOCAL_BUFFER_SIZE
	67	*/
	68	static const char *freezer_state_strs[] = {
81dcf33c	69	"THAWED",
dc52ddc0 MH	70	"FREEZING",
	71	"FROZEN",
	72	};
	73
	74	/*
	75	* State diagram
	76	* Transitions are caused by userspace writes to the freezer.state file.
	77	* The values in parenthesis are state labels. The rest are edge labels.
	78	*
81dcf33c MH	79	* (THAWED) --FROZEN--> (FREEZING) --FROZEN--> (FROZEN)
	80	* ^ ^ \| \|
	81	* \| \_______THAWED_______/ \|
	82	* \__________________________THAWED____________/
dc52ddc0 MH	83	*/
	84
	85	struct cgroup_subsys freezer_subsys;
	86
	87	/* Locks taken and their ordering
	88	* ------------------------------
dc52ddc0	89	* cgroup_mutex (AKA cgroup_lock)
dc52ddc0	90	* freezer->lock
8f77578c MH	91	* css_set_lock
8f77578c MH	92	* task->alloc_lock (AKA task_lock)
dc52ddc0 MH	93	* task->sighand->siglock
	94	*
	95	* cgroup code forces css_set_lock to be taken before task->alloc_lock
	96	*
	97	* freezer_create(), freezer_destroy():
	98	* cgroup_mutex [ by cgroup core ]
	99	*
8f77578c MH	100	* freezer_can_attach():
8f77578c MH	101	* cgroup_mutex (held by caller of can_attach)
dc52ddc0	102	*
dc52ddc0	103	* freezer_fork() (preserving fork() performance means can't take cgroup_mutex):
dc52ddc0 MH	104	* freezer->lock
	105	* sighand->siglock (if the cgroup is freezing)
	106	*
	107	* freezer_read():
	108	* cgroup_mutex
	109	* freezer->lock
8f77578c MH	110	* write_lock css_set_lock (cgroup iterator start)
8f77578c MH	111	* task->alloc_lock
dc52ddc0 MH	112	* read_lock css_set_lock (cgroup iterator start)
	113	*
	114	* freezer_write() (freeze):
	115	* cgroup_mutex
	116	* freezer->lock
8f77578c MH	117	* write_lock css_set_lock (cgroup iterator start)
8f77578c MH	118	* task->alloc_lock
dc52ddc0	119	* read_lock css_set_lock (cgroup iterator start)
8f77578c	120	* sighand->siglock (fake signal delivery inside freeze_task())
dc52ddc0 MH	121	*
	122	* freezer_write() (unfreeze):
	123	* cgroup_mutex
	124	* freezer->lock
8f77578c MH	125	* write_lock css_set_lock (cgroup iterator start)
8f77578c MH	126	* task->alloc_lock
dc52ddc0	127	* read_lock css_set_lock (cgroup iterator start)
a5be2d0d	128	* task->alloc_lock (inside __thaw_task(), prevents race with refrigerator())
dc52ddc0 MH	129	* sighand->siglock
	130	*/
	131	static struct cgroup_subsys_state freezer_create(struct cgroup_subsys ss,
	132	struct cgroup *cgroup)
	133	{
	134	struct freezer *freezer;
	135
	136	freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL);
	137	if (!freezer)
	138	return ERR_PTR(-ENOMEM);
	139
	140	spin_lock_init(&freezer->lock);
81dcf33c	141	freezer->state = CGROUP_THAWED;
dc52ddc0 MH	142	return &freezer->css;
	143	}
	144
	145	static void freezer_destroy(struct cgroup_subsys *ss,
	146	struct cgroup *cgroup)
	147	{
a3201227 TH	148	struct freezer *freezer = cgroup_freezer(cgroup);
	149
	150	if (freezer->state != CGROUP_THAWED)
	151	atomic_dec(&system_freezing_cnt);
	152	kfree(freezer);
dc52ddc0 MH	153	}
dc52ddc0 MH	154
884a45d9 MH	155	/* task is frozen or will freeze immediately when next it gets woken */
	156	static bool is_task_frozen_enough(struct task_struct *task)
	157	{
	158	return frozen(task) \|\|
	159	(task_is_stopped_or_traced(task) && freezing(task));
	160	}
	161
957a4eea MH	162	/*
	163	* The call to cgroup_lock() in the freezer.state write method prevents
	164	* a write to that file racing against an attach, and hence the
	165	* can_attach() result will remain valid until the attach completes.
	166	*/
dc52ddc0 MH	167	static int freezer_can_attach(struct cgroup_subsys *ss,
dc52ddc0 MH	168	struct cgroup *new_cgroup,
2f7ee569	169	struct cgroup_taskset *tset)
dc52ddc0 MH	170	{
dc52ddc0 MH	171	struct freezer *freezer;
bb9d97b6	172	struct task_struct *task;
957a4eea	173
80a6a2cf LZ	174	/*
80a6a2cf LZ	175	* Anything frozen can't move or be moved to/from.
80a6a2cf	176	*/
bb9d97b6 TH	177	cgroup_taskset_for_each(task, new_cgroup, tset)
	178	if (cgroup_freezing(task))
	179	return -EBUSY;
957a4eea	180
0bdba580 TB	181	freezer = cgroup_freezer(new_cgroup);
0bdba580 TB	182	if (freezer->state != CGROUP_THAWED)
957a4eea	183	return -EBUSY;
dc52ddc0	184
f780bdb7 BB	185	return 0;
	186	}
	187
dc52ddc0 MH	188	static void freezer_fork(struct cgroup_subsys ss, struct task_struct task)
	189	{
	190	struct freezer *freezer;
	191
68744676 LZ	192	/*
	193	* No lock is needed, since the task isn't on tasklist yet,
	194	* so it can't be moved to another cgroup, which means the
	195	* freezer won't be removed and will be valid during this
8b46f880 PM	196	* function call. Nevertheless, apply RCU read-side critical
8b46f880 PM	197	* section to suppress RCU lockdep false positives.
68744676	198	*/
8b46f880	199	rcu_read_lock();
dc52ddc0	200	freezer = task_freezer(task);
8b46f880	201	rcu_read_unlock();
dc52ddc0	202
3b1b3f6e LZ	203	/*
	204	* The root cgroup is non-freezable, so we can skip the
	205	* following check.
	206	*/
	207	if (!freezer->css.cgroup->parent)
	208	return;
	209
dc52ddc0	210	spin_lock_irq(&freezer->lock);
7ccb9743 LZ	211	BUG_ON(freezer->state == CGROUP_FROZEN);
7ccb9743 LZ	212
81dcf33c MH	213	/* Locking avoids race with FREEZING -> THAWED transitions. */
81dcf33c MH	214	if (freezer->state == CGROUP_FREEZING)
839e3407	215	freeze_task(task);
dc52ddc0 MH	216	spin_unlock_irq(&freezer->lock);
	217	}
	218
	219	/*
	220	* caller must hold freezer->lock
	221	*/
2d3cbf8b	222	static void update_if_frozen(struct cgroup *cgroup,
1aece348	223	struct freezer *freezer)
dc52ddc0 MH	224	{
	225	struct cgroup_iter it;
	226	struct task_struct *task;
	227	unsigned int nfrozen = 0, ntotal = 0;
2d3cbf8b	228	enum freezer_state old_state = freezer->state;
dc52ddc0 MH	229
	230	cgroup_iter_start(cgroup, &it);
	231	while ((task = cgroup_iter_next(cgroup, &it))) {
	232	ntotal++;
b00f4dc5	233	if (freezing(task) && is_task_frozen_enough(task))
dc52ddc0 MH	234	nfrozen++;
	235	}
	236
2d3cbf8b TB	237	if (old_state == CGROUP_THAWED) {
	238	BUG_ON(nfrozen > 0);
	239	} else if (old_state == CGROUP_FREEZING) {
	240	if (nfrozen == ntotal)
	241	freezer->state = CGROUP_FROZEN;
	242	} else { /* old_state == CGROUP_FROZEN */
	243	BUG_ON(nfrozen != ntotal);
	244	}
	245
dc52ddc0 MH	246	cgroup_iter_end(cgroup, &it);
	247	}
	248
	249	static int freezer_read(struct cgroup cgroup, struct cftype cft,
	250	struct seq_file *m)
	251	{
	252	struct freezer *freezer;
	253	enum freezer_state state;
	254
	255	if (!cgroup_lock_live_group(cgroup))
	256	return -ENODEV;
	257
	258	freezer = cgroup_freezer(cgroup);
	259	spin_lock_irq(&freezer->lock);
	260	state = freezer->state;
81dcf33c	261	if (state == CGROUP_FREEZING) {
dc52ddc0 MH	262	/* We change from FREEZING to FROZEN lazily if the cgroup was
dc52ddc0 MH	263	* only partially frozen when we exitted write. */
2d3cbf8b	264	update_if_frozen(cgroup, freezer);
dc52ddc0 MH	265	state = freezer->state;
	266	}
	267	spin_unlock_irq(&freezer->lock);
	268	cgroup_unlock();
	269
	270	seq_puts(m, freezer_state_strs[state]);
	271	seq_putc(m, '\n');
	272	return 0;
	273	}
	274
	275	static int try_to_freeze_cgroup(struct cgroup cgroup, struct freezer freezer)
	276	{
	277	struct cgroup_iter it;
	278	struct task_struct *task;
	279	unsigned int num_cant_freeze_now = 0;
	280
dc52ddc0 MH	281	cgroup_iter_start(cgroup, &it);
dc52ddc0 MH	282	while ((task = cgroup_iter_next(cgroup, &it))) {
839e3407	283	if (!freeze_task(task))
dc52ddc0	284	continue;
884a45d9	285	if (is_task_frozen_enough(task))
dc52ddc0 MH	286	continue;
	287	if (!freezing(task) && !freezer_should_skip(task))
	288	num_cant_freeze_now++;
	289	}
	290	cgroup_iter_end(cgroup, &it);
	291
	292	return num_cant_freeze_now ? -EBUSY : 0;
	293	}
	294
00c2e63c	295	static void unfreeze_cgroup(struct cgroup cgroup, struct freezer freezer)
dc52ddc0 MH	296	{
	297	struct cgroup_iter it;
	298	struct task_struct *task;
	299
	300	cgroup_iter_start(cgroup, &it);
a5be2d0d TH	301	while ((task = cgroup_iter_next(cgroup, &it)))
a5be2d0d TH	302	__thaw_task(task);
dc52ddc0	303	cgroup_iter_end(cgroup, &it);
dc52ddc0 MH	304	}
	305
	306	static int freezer_change_state(struct cgroup *cgroup,
	307	enum freezer_state goal_state)
	308	{
	309	struct freezer *freezer;
	310	int retval = 0;
	311
	312	freezer = cgroup_freezer(cgroup);
51308ee5	313
dc52ddc0	314	spin_lock_irq(&freezer->lock);
51308ee5	315
2d3cbf8b	316	update_if_frozen(cgroup, freezer);
51308ee5 LZ	317
51308ee5 LZ	318	switch (goal_state) {
81dcf33c	319	case CGROUP_THAWED:
a3201227 TH	320	if (freezer->state != CGROUP_THAWED)
a3201227 TH	321	atomic_dec(&system_freezing_cnt);
22b4e111	322	freezer->state = CGROUP_THAWED;
51308ee5	323	unfreeze_cgroup(cgroup, freezer);
dc52ddc0	324	break;
81dcf33c	325	case CGROUP_FROZEN:
a3201227 TH	326	if (freezer->state == CGROUP_THAWED)
a3201227 TH	327	atomic_inc(&system_freezing_cnt);
22b4e111	328	freezer->state = CGROUP_FREEZING;
51308ee5	329	retval = try_to_freeze_cgroup(cgroup, freezer);
dc52ddc0 MH	330	break;
dc52ddc0 MH	331	default:
51308ee5	332	BUG();
dc52ddc0	333	}
22b4e111	334
dc52ddc0 MH	335	spin_unlock_irq(&freezer->lock);
	336
	337	return retval;
	338	}
	339
	340	static int freezer_write(struct cgroup *cgroup,
	341	struct cftype *cft,
	342	const char *buffer)
	343	{
	344	int retval;
	345	enum freezer_state goal_state;
	346
81dcf33c MH	347	if (strcmp(buffer, freezer_state_strs[CGROUP_THAWED]) == 0)
	348	goal_state = CGROUP_THAWED;
	349	else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0)
	350	goal_state = CGROUP_FROZEN;
dc52ddc0	351	else
3b1b3f6e	352	return -EINVAL;
dc52ddc0 MH	353
	354	if (!cgroup_lock_live_group(cgroup))
	355	return -ENODEV;
	356	retval = freezer_change_state(cgroup, goal_state);
	357	cgroup_unlock();
	358	return retval;
	359	}
	360
	361	static struct cftype files[] = {
	362	{
	363	.name = "state",
	364	.read_seq_string = freezer_read,
	365	.write_string = freezer_write,
	366	},
	367	};
	368
	369	static int freezer_populate(struct cgroup_subsys ss, struct cgroup cgroup)
	370	{
3b1b3f6e LZ	371	if (!cgroup->parent)
3b1b3f6e LZ	372	return 0;
dc52ddc0 MH	373	return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files));
	374	}
	375
	376	struct cgroup_subsys freezer_subsys = {
	377	.name = "freezer",
	378	.create = freezer_create,
	379	.destroy = freezer_destroy,
	380	.populate = freezer_populate,
	381	.subsys_id = freezer_subsys_id,
	382	.can_attach = freezer_can_attach,
dc52ddc0	383	.fork = freezer_fork,
dc52ddc0	384	};