kthread: rename probe_kthread_data() to kthread_probe_data()
[linux-2.6-block.git] / kernel / cgroup_freezer.c
CommitLineData
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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>
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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>
e5ced8eb 24#include <linux/mutex.h>
dc52ddc0 25
ef9fe980
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26/*
27 * A cgroup is freezing if any FREEZING flags are set. FREEZING_SELF is
28 * set if "FROZEN" is written to freezer.state cgroupfs file, and cleared
29 * for "THAWED". FREEZING_PARENT is set if the parent freezer is FREEZING
30 * for whatever reason. IOW, a cgroup has FREEZING_PARENT set if one of
31 * its ancestors has FREEZING_SELF set.
32 */
d6a2fe13 33enum freezer_state_flags {
5300a9b3 34 CGROUP_FREEZER_ONLINE = (1 << 0), /* freezer is fully online */
a2252180
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35 CGROUP_FREEZING_SELF = (1 << 1), /* this freezer is freezing */
36 CGROUP_FREEZING_PARENT = (1 << 2), /* the parent freezer is freezing */
d6a2fe13 37 CGROUP_FROZEN = (1 << 3), /* this and its descendants frozen */
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38
39 /* mask for all FREEZING flags */
40 CGROUP_FREEZING = CGROUP_FREEZING_SELF | CGROUP_FREEZING_PARENT,
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41};
42
43struct freezer {
bcd66c89 44 struct cgroup_subsys_state css;
d6a2fe13 45 unsigned int state;
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46};
47
e5ced8eb
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48static DEFINE_MUTEX(freezer_mutex);
49
a7c6d554
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50static inline struct freezer *css_freezer(struct cgroup_subsys_state *css)
51{
52 return css ? container_of(css, struct freezer, css) : NULL;
53}
54
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55static inline struct freezer *task_freezer(struct task_struct *task)
56{
073219e9 57 return css_freezer(task_css(task, freezer_cgrp_id));
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58}
59
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60static struct freezer *parent_freezer(struct freezer *freezer)
61{
5c9d535b 62 return css_freezer(freezer->css.parent);
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63}
64
22b4e111 65bool cgroup_freezing(struct task_struct *task)
dc52ddc0 66{
22b4e111 67 bool ret;
dc52ddc0 68
22b4e111 69 rcu_read_lock();
d6a2fe13 70 ret = task_freezer(task)->state & CGROUP_FREEZING;
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71 rcu_read_unlock();
72
73 return ret;
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74}
75
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76static const char *freezer_state_strs(unsigned int state)
77{
78 if (state & CGROUP_FROZEN)
79 return "FROZEN";
80 if (state & CGROUP_FREEZING)
81 return "FREEZING";
82 return "THAWED";
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83};
84
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85static struct cgroup_subsys_state *
86freezer_css_alloc(struct cgroup_subsys_state *parent_css)
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87{
88 struct freezer *freezer;
89
90 freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL);
91 if (!freezer)
92 return ERR_PTR(-ENOMEM);
93
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94 return &freezer->css;
95}
96
5300a9b3 97/**
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98 * freezer_css_online - commit creation of a freezer css
99 * @css: css being created
5300a9b3 100 *
eb95419b 101 * We're committing to creation of @css. Mark it online and inherit
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102 * parent's freezing state while holding both parent's and our
103 * freezer->lock.
5300a9b3 104 */
eb95419b 105static int freezer_css_online(struct cgroup_subsys_state *css)
dc52ddc0 106{
eb95419b 107 struct freezer *freezer = css_freezer(css);
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108 struct freezer *parent = parent_freezer(freezer);
109
e5ced8eb 110 mutex_lock(&freezer_mutex);
a3201227 111
5300a9b3 112 freezer->state |= CGROUP_FREEZER_ONLINE;
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113
114 if (parent && (parent->state & CGROUP_FREEZING)) {
115 freezer->state |= CGROUP_FREEZING_PARENT | CGROUP_FROZEN;
116 atomic_inc(&system_freezing_cnt);
117 }
118
e5ced8eb 119 mutex_unlock(&freezer_mutex);
b1929db4 120 return 0;
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121}
122
123/**
eb95419b
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124 * freezer_css_offline - initiate destruction of a freezer css
125 * @css: css being destroyed
5300a9b3 126 *
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127 * @css is going away. Mark it dead and decrement system_freezing_count if
128 * it was holding one.
5300a9b3 129 */
eb95419b 130static void freezer_css_offline(struct cgroup_subsys_state *css)
5300a9b3 131{
eb95419b 132 struct freezer *freezer = css_freezer(css);
5300a9b3 133
e5ced8eb 134 mutex_lock(&freezer_mutex);
5300a9b3 135
d6a2fe13 136 if (freezer->state & CGROUP_FREEZING)
a3201227 137 atomic_dec(&system_freezing_cnt);
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138
139 freezer->state = 0;
140
e5ced8eb 141 mutex_unlock(&freezer_mutex);
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142}
143
eb95419b 144static void freezer_css_free(struct cgroup_subsys_state *css)
5300a9b3 145{
eb95419b 146 kfree(css_freezer(css));
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147}
148
957a4eea 149/*
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150 * Tasks can be migrated into a different freezer anytime regardless of its
151 * current state. freezer_attach() is responsible for making new tasks
152 * conform to the current state.
153 *
154 * Freezer state changes and task migration are synchronized via
155 * @freezer->lock. freezer_attach() makes the new tasks conform to the
156 * current state and all following state changes can see the new tasks.
957a4eea 157 */
1f7dd3e5 158static void freezer_attach(struct cgroup_taskset *tset)
dc52ddc0 159{
bb9d97b6 160 struct task_struct *task;
1f7dd3e5 161 struct cgroup_subsys_state *new_css;
957a4eea 162
e5ced8eb 163 mutex_lock(&freezer_mutex);
8755ade6 164
80a6a2cf 165 /*
eb95419b 166 * Make the new tasks conform to the current state of @new_css.
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167 * For simplicity, when migrating any task to a FROZEN cgroup, we
168 * revert it to FREEZING and let update_if_frozen() determine the
169 * correct state later.
170 *
eb95419b 171 * Tasks in @tset are on @new_css but may not conform to its
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172 * current state before executing the following - !frozen tasks may
173 * be visible in a FROZEN cgroup and frozen tasks in a THAWED one.
80a6a2cf 174 */
1f7dd3e5 175 cgroup_taskset_for_each(task, new_css, tset) {
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176 struct freezer *freezer = css_freezer(new_css);
177
d6a2fe13 178 if (!(freezer->state & CGROUP_FREEZING)) {
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179 __thaw_task(task);
180 } else {
181 freeze_task(task);
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182 /* clear FROZEN and propagate upwards */
183 while (freezer && (freezer->state & CGROUP_FROZEN)) {
184 freezer->state &= ~CGROUP_FROZEN;
185 freezer = parent_freezer(freezer);
186 }
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187 }
188 }
dc52ddc0 189
e5ced8eb 190 mutex_unlock(&freezer_mutex);
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191}
192
a60bed29
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193/**
194 * freezer_fork - cgroup post fork callback
195 * @task: a task which has just been forked
196 *
197 * @task has just been created and should conform to the current state of
198 * the cgroup_freezer it belongs to. This function may race against
199 * freezer_attach(). Losing to freezer_attach() means that we don't have
200 * to do anything as freezer_attach() will put @task into the appropriate
201 * state.
202 */
b53202e6 203static void freezer_fork(struct task_struct *task)
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204{
205 struct freezer *freezer;
206
3b1b3f6e 207 /*
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208 * The root cgroup is non-freezable, so we can skip locking the
209 * freezer. This is safe regardless of race with task migration.
210 * If we didn't race or won, skipping is obviously the right thing
211 * to do. If we lost and root is the new cgroup, noop is still the
212 * right thing to do.
3b1b3f6e 213 */
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214 if (task_css_is_root(task, freezer_cgrp_id))
215 return;
3b1b3f6e 216
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217 mutex_lock(&freezer_mutex);
218 rcu_read_lock();
219
220 freezer = task_freezer(task);
221 if (freezer->state & CGROUP_FREEZING)
839e3407 222 freeze_task(task);
e5ced8eb 223
5edee61e 224 rcu_read_unlock();
e5ced8eb 225 mutex_unlock(&freezer_mutex);
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226}
227
ef9fe980
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228/**
229 * update_if_frozen - update whether a cgroup finished freezing
182446d0 230 * @css: css of interest
ef9fe980
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231 *
232 * Once FREEZING is initiated, transition to FROZEN is lazily updated by
233 * calling this function. If the current state is FREEZING but not FROZEN,
234 * this function checks whether all tasks of this cgroup and the descendant
235 * cgroups finished freezing and, if so, sets FROZEN.
236 *
237 * The caller is responsible for grabbing RCU read lock and calling
238 * update_if_frozen() on all descendants prior to invoking this function.
b4d18311
TH
239 *
240 * Task states and freezer state might disagree while tasks are being
182446d0 241 * migrated into or out of @css, so we can't verify task states against
ead5c473 242 * @freezer state here. See freezer_attach() for details.
dc52ddc0 243 */
182446d0 244static void update_if_frozen(struct cgroup_subsys_state *css)
dc52ddc0 245{
182446d0 246 struct freezer *freezer = css_freezer(css);
492eb21b 247 struct cgroup_subsys_state *pos;
72ec7029 248 struct css_task_iter it;
dc52ddc0 249 struct task_struct *task;
b4d18311 250
e5ced8eb 251 lockdep_assert_held(&freezer_mutex);
ef9fe980 252
d6a2fe13
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253 if (!(freezer->state & CGROUP_FREEZING) ||
254 (freezer->state & CGROUP_FROZEN))
e5ced8eb 255 return;
ef9fe980
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256
257 /* are all (live) children frozen? */
e5ced8eb 258 rcu_read_lock();
492eb21b
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259 css_for_each_child(pos, css) {
260 struct freezer *child = css_freezer(pos);
dc52ddc0 261
ef9fe980 262 if ((child->state & CGROUP_FREEZER_ONLINE) &&
36e9d2eb
TH
263 !(child->state & CGROUP_FROZEN)) {
264 rcu_read_unlock();
e5ced8eb 265 return;
36e9d2eb 266 }
ef9fe980 267 }
e5ced8eb 268 rcu_read_unlock();
ef9fe980
TH
269
270 /* are all tasks frozen? */
72ec7029 271 css_task_iter_start(css, &it);
b4d18311 272
72ec7029 273 while ((task = css_task_iter_next(&it))) {
3c426d5e 274 if (freezing(task)) {
3c426d5e
TH
275 /*
276 * freezer_should_skip() indicates that the task
277 * should be skipped when determining freezing
278 * completion. Consider it frozen in addition to
279 * the usual frozen condition.
280 */
5d8f72b5 281 if (!frozen(task) && !freezer_should_skip(task))
ef9fe980 282 goto out_iter_end;
3c426d5e 283 }
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284 }
285
d6a2fe13 286 freezer->state |= CGROUP_FROZEN;
ef9fe980 287out_iter_end:
72ec7029 288 css_task_iter_end(&it);
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289}
290
2da8ca82 291static int freezer_read(struct seq_file *m, void *v)
dc52ddc0 292{
2da8ca82 293 struct cgroup_subsys_state *css = seq_css(m), *pos;
dc52ddc0 294
e5ced8eb 295 mutex_lock(&freezer_mutex);
ef9fe980 296 rcu_read_lock();
dc52ddc0 297
ef9fe980 298 /* update states bottom-up */
e5ced8eb 299 css_for_each_descendant_post(pos, css) {
ec903c0c 300 if (!css_tryget_online(pos))
e5ced8eb
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301 continue;
302 rcu_read_unlock();
303
492eb21b 304 update_if_frozen(pos);
ef9fe980 305
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306 rcu_read_lock();
307 css_put(pos);
308 }
309
ef9fe980 310 rcu_read_unlock();
e5ced8eb 311 mutex_unlock(&freezer_mutex);
ef9fe980 312
182446d0 313 seq_puts(m, freezer_state_strs(css_freezer(css)->state));
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314 seq_putc(m, '\n');
315 return 0;
316}
317
bcd66c89 318static void freeze_cgroup(struct freezer *freezer)
dc52ddc0 319{
72ec7029 320 struct css_task_iter it;
dc52ddc0 321 struct task_struct *task;
dc52ddc0 322
72ec7029
TH
323 css_task_iter_start(&freezer->css, &it);
324 while ((task = css_task_iter_next(&it)))
51f246ed 325 freeze_task(task);
72ec7029 326 css_task_iter_end(&it);
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327}
328
bcd66c89 329static void unfreeze_cgroup(struct freezer *freezer)
dc52ddc0 330{
72ec7029 331 struct css_task_iter it;
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332 struct task_struct *task;
333
72ec7029
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334 css_task_iter_start(&freezer->css, &it);
335 while ((task = css_task_iter_next(&it)))
a5be2d0d 336 __thaw_task(task);
72ec7029 337 css_task_iter_end(&it);
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338}
339
04a4ec32
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340/**
341 * freezer_apply_state - apply state change to a single cgroup_freezer
342 * @freezer: freezer to apply state change to
343 * @freeze: whether to freeze or unfreeze
a2252180
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344 * @state: CGROUP_FREEZING_* flag to set or clear
345 *
346 * Set or clear @state on @cgroup according to @freeze, and perform
347 * freezing or thawing as necessary.
04a4ec32 348 */
a2252180
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349static void freezer_apply_state(struct freezer *freezer, bool freeze,
350 unsigned int state)
dc52ddc0 351{
ead5c473 352 /* also synchronizes against task migration, see freezer_attach() */
e5ced8eb 353 lockdep_assert_held(&freezer_mutex);
51308ee5 354
5300a9b3
TH
355 if (!(freezer->state & CGROUP_FREEZER_ONLINE))
356 return;
357
04a4ec32 358 if (freeze) {
d6a2fe13 359 if (!(freezer->state & CGROUP_FREEZING))
a3201227 360 atomic_inc(&system_freezing_cnt);
a2252180 361 freezer->state |= state;
bcd66c89 362 freeze_cgroup(freezer);
04a4ec32 363 } else {
a2252180
TH
364 bool was_freezing = freezer->state & CGROUP_FREEZING;
365
366 freezer->state &= ~state;
367
368 if (!(freezer->state & CGROUP_FREEZING)) {
369 if (was_freezing)
370 atomic_dec(&system_freezing_cnt);
371 freezer->state &= ~CGROUP_FROZEN;
372 unfreeze_cgroup(freezer);
373 }
dc52ddc0 374 }
04a4ec32 375}
22b4e111 376
04a4ec32
TH
377/**
378 * freezer_change_state - change the freezing state of a cgroup_freezer
379 * @freezer: freezer of interest
380 * @freeze: whether to freeze or thaw
381 *
ef9fe980
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382 * Freeze or thaw @freezer according to @freeze. The operations are
383 * recursive - all descendants of @freezer will be affected.
04a4ec32
TH
384 */
385static void freezer_change_state(struct freezer *freezer, bool freeze)
386{
492eb21b 387 struct cgroup_subsys_state *pos;
ef9fe980 388
ef9fe980
TH
389 /*
390 * Update all its descendants in pre-order traversal. Each
391 * descendant will try to inherit its parent's FREEZING state as
392 * CGROUP_FREEZING_PARENT.
393 */
e5ced8eb 394 mutex_lock(&freezer_mutex);
ef9fe980 395 rcu_read_lock();
492eb21b
TH
396 css_for_each_descendant_pre(pos, &freezer->css) {
397 struct freezer *pos_f = css_freezer(pos);
ef9fe980
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398 struct freezer *parent = parent_freezer(pos_f);
399
ec903c0c 400 if (!css_tryget_online(pos))
e5ced8eb
TH
401 continue;
402 rcu_read_unlock();
bd8815a6 403
e5ced8eb 404 if (pos_f == freezer)
bd8815a6
TH
405 freezer_apply_state(pos_f, freeze,
406 CGROUP_FREEZING_SELF);
e5ced8eb 407 else
bd8815a6
TH
408 freezer_apply_state(pos_f,
409 parent->state & CGROUP_FREEZING,
410 CGROUP_FREEZING_PARENT);
bd8815a6 411
e5ced8eb
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412 rcu_read_lock();
413 css_put(pos);
ef9fe980
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414 }
415 rcu_read_unlock();
e5ced8eb 416 mutex_unlock(&freezer_mutex);
dc52ddc0
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417}
418
451af504
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419static ssize_t freezer_write(struct kernfs_open_file *of,
420 char *buf, size_t nbytes, loff_t off)
dc52ddc0 421{
04a4ec32 422 bool freeze;
dc52ddc0 423
451af504
TH
424 buf = strstrip(buf);
425
426 if (strcmp(buf, freezer_state_strs(0)) == 0)
04a4ec32 427 freeze = false;
451af504 428 else if (strcmp(buf, freezer_state_strs(CGROUP_FROZEN)) == 0)
04a4ec32 429 freeze = true;
dc52ddc0 430 else
3b1b3f6e 431 return -EINVAL;
dc52ddc0 432
451af504
TH
433 freezer_change_state(css_freezer(of_css(of)), freeze);
434 return nbytes;
dc52ddc0
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435}
436
182446d0
TH
437static u64 freezer_self_freezing_read(struct cgroup_subsys_state *css,
438 struct cftype *cft)
a2252180 439{
182446d0 440 struct freezer *freezer = css_freezer(css);
a2252180
TH
441
442 return (bool)(freezer->state & CGROUP_FREEZING_SELF);
443}
444
182446d0
TH
445static u64 freezer_parent_freezing_read(struct cgroup_subsys_state *css,
446 struct cftype *cft)
a2252180 447{
182446d0 448 struct freezer *freezer = css_freezer(css);
a2252180
TH
449
450 return (bool)(freezer->state & CGROUP_FREEZING_PARENT);
451}
452
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453static struct cftype files[] = {
454 {
455 .name = "state",
4baf6e33 456 .flags = CFTYPE_NOT_ON_ROOT,
2da8ca82 457 .seq_show = freezer_read,
451af504 458 .write = freezer_write,
dc52ddc0 459 },
a2252180
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460 {
461 .name = "self_freezing",
462 .flags = CFTYPE_NOT_ON_ROOT,
463 .read_u64 = freezer_self_freezing_read,
464 },
465 {
466 .name = "parent_freezing",
467 .flags = CFTYPE_NOT_ON_ROOT,
468 .read_u64 = freezer_parent_freezing_read,
469 },
4baf6e33 470 { } /* terminate */
dc52ddc0
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471};
472
073219e9 473struct cgroup_subsys freezer_cgrp_subsys = {
92fb9748
TH
474 .css_alloc = freezer_css_alloc,
475 .css_online = freezer_css_online,
476 .css_offline = freezer_css_offline,
477 .css_free = freezer_css_free,
8755ade6 478 .attach = freezer_attach,
dc52ddc0 479 .fork = freezer_fork,
5577964e 480 .legacy_cftypes = files,
dc52ddc0 481};