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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 | ||
ef9fe980 TH |
25 | /* |
26 | * A cgroup is freezing if any FREEZING flags are set. FREEZING_SELF is | |
27 | * set if "FROZEN" is written to freezer.state cgroupfs file, and cleared | |
28 | * for "THAWED". FREEZING_PARENT is set if the parent freezer is FREEZING | |
29 | * for whatever reason. IOW, a cgroup has FREEZING_PARENT set if one of | |
30 | * its ancestors has FREEZING_SELF set. | |
31 | */ | |
d6a2fe13 | 32 | enum freezer_state_flags { |
5300a9b3 | 33 | CGROUP_FREEZER_ONLINE = (1 << 0), /* freezer is fully online */ |
a2252180 TH |
34 | CGROUP_FREEZING_SELF = (1 << 1), /* this freezer is freezing */ |
35 | CGROUP_FREEZING_PARENT = (1 << 2), /* the parent freezer is freezing */ | |
d6a2fe13 | 36 | CGROUP_FROZEN = (1 << 3), /* this and its descendants frozen */ |
a2252180 TH |
37 | |
38 | /* mask for all FREEZING flags */ | |
39 | CGROUP_FREEZING = CGROUP_FREEZING_SELF | CGROUP_FREEZING_PARENT, | |
dc52ddc0 MH |
40 | }; |
41 | ||
42 | struct freezer { | |
bcd66c89 | 43 | struct cgroup_subsys_state css; |
d6a2fe13 | 44 | unsigned int state; |
bcd66c89 | 45 | spinlock_t lock; |
dc52ddc0 MH |
46 | }; |
47 | ||
a7c6d554 TH |
48 | static inline struct freezer *css_freezer(struct cgroup_subsys_state *css) |
49 | { | |
50 | return css ? container_of(css, struct freezer, css) : NULL; | |
51 | } | |
52 | ||
dc52ddc0 MH |
53 | static inline struct freezer *task_freezer(struct task_struct *task) |
54 | { | |
073219e9 | 55 | return css_freezer(task_css(task, freezer_cgrp_id)); |
dc52ddc0 MH |
56 | } |
57 | ||
ef9fe980 TH |
58 | static struct freezer *parent_freezer(struct freezer *freezer) |
59 | { | |
63876986 | 60 | return css_freezer(css_parent(&freezer->css)); |
ef9fe980 TH |
61 | } |
62 | ||
22b4e111 | 63 | bool cgroup_freezing(struct task_struct *task) |
dc52ddc0 | 64 | { |
22b4e111 | 65 | bool ret; |
dc52ddc0 | 66 | |
22b4e111 | 67 | rcu_read_lock(); |
d6a2fe13 | 68 | ret = task_freezer(task)->state & CGROUP_FREEZING; |
22b4e111 TH |
69 | rcu_read_unlock(); |
70 | ||
71 | return ret; | |
dc52ddc0 MH |
72 | } |
73 | ||
74 | /* | |
75 | * cgroups_write_string() limits the size of freezer state strings to | |
76 | * CGROUP_LOCAL_BUFFER_SIZE | |
77 | */ | |
d6a2fe13 TH |
78 | static const char *freezer_state_strs(unsigned int state) |
79 | { | |
80 | if (state & CGROUP_FROZEN) | |
81 | return "FROZEN"; | |
82 | if (state & CGROUP_FREEZING) | |
83 | return "FREEZING"; | |
84 | return "THAWED"; | |
dc52ddc0 MH |
85 | }; |
86 | ||
eb95419b TH |
87 | static struct cgroup_subsys_state * |
88 | freezer_css_alloc(struct cgroup_subsys_state *parent_css) | |
dc52ddc0 MH |
89 | { |
90 | struct freezer *freezer; | |
91 | ||
92 | freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL); | |
93 | if (!freezer) | |
94 | return ERR_PTR(-ENOMEM); | |
95 | ||
96 | spin_lock_init(&freezer->lock); | |
dc52ddc0 MH |
97 | return &freezer->css; |
98 | } | |
99 | ||
5300a9b3 | 100 | /** |
eb95419b TH |
101 | * freezer_css_online - commit creation of a freezer css |
102 | * @css: css being created | |
5300a9b3 | 103 | * |
eb95419b | 104 | * We're committing to creation of @css. Mark it online and inherit |
ef9fe980 TH |
105 | * parent's freezing state while holding both parent's and our |
106 | * freezer->lock. | |
5300a9b3 | 107 | */ |
eb95419b | 108 | static int freezer_css_online(struct cgroup_subsys_state *css) |
dc52ddc0 | 109 | { |
eb95419b | 110 | struct freezer *freezer = css_freezer(css); |
ef9fe980 TH |
111 | struct freezer *parent = parent_freezer(freezer); |
112 | ||
113 | /* | |
114 | * The following double locking and freezing state inheritance | |
115 | * guarantee that @cgroup can never escape ancestors' freezing | |
492eb21b | 116 | * states. See css_for_each_descendant_pre() for details. |
ef9fe980 TH |
117 | */ |
118 | if (parent) | |
119 | spin_lock_irq(&parent->lock); | |
120 | spin_lock_nested(&freezer->lock, SINGLE_DEPTH_NESTING); | |
a3201227 | 121 | |
5300a9b3 | 122 | freezer->state |= CGROUP_FREEZER_ONLINE; |
ef9fe980 TH |
123 | |
124 | if (parent && (parent->state & CGROUP_FREEZING)) { | |
125 | freezer->state |= CGROUP_FREEZING_PARENT | CGROUP_FROZEN; | |
126 | atomic_inc(&system_freezing_cnt); | |
127 | } | |
128 | ||
129 | spin_unlock(&freezer->lock); | |
130 | if (parent) | |
131 | spin_unlock_irq(&parent->lock); | |
b1929db4 TH |
132 | |
133 | return 0; | |
5300a9b3 TH |
134 | } |
135 | ||
136 | /** | |
eb95419b TH |
137 | * freezer_css_offline - initiate destruction of a freezer css |
138 | * @css: css being destroyed | |
5300a9b3 | 139 | * |
eb95419b TH |
140 | * @css is going away. Mark it dead and decrement system_freezing_count if |
141 | * it was holding one. | |
5300a9b3 | 142 | */ |
eb95419b | 143 | static void freezer_css_offline(struct cgroup_subsys_state *css) |
5300a9b3 | 144 | { |
eb95419b | 145 | struct freezer *freezer = css_freezer(css); |
5300a9b3 TH |
146 | |
147 | spin_lock_irq(&freezer->lock); | |
148 | ||
d6a2fe13 | 149 | if (freezer->state & CGROUP_FREEZING) |
a3201227 | 150 | atomic_dec(&system_freezing_cnt); |
5300a9b3 TH |
151 | |
152 | freezer->state = 0; | |
153 | ||
154 | spin_unlock_irq(&freezer->lock); | |
155 | } | |
156 | ||
eb95419b | 157 | static void freezer_css_free(struct cgroup_subsys_state *css) |
5300a9b3 | 158 | { |
eb95419b | 159 | kfree(css_freezer(css)); |
dc52ddc0 MH |
160 | } |
161 | ||
957a4eea | 162 | /* |
ead5c473 TH |
163 | * Tasks can be migrated into a different freezer anytime regardless of its |
164 | * current state. freezer_attach() is responsible for making new tasks | |
165 | * conform to the current state. | |
166 | * | |
167 | * Freezer state changes and task migration are synchronized via | |
168 | * @freezer->lock. freezer_attach() makes the new tasks conform to the | |
169 | * current state and all following state changes can see the new tasks. | |
957a4eea | 170 | */ |
eb95419b TH |
171 | static void freezer_attach(struct cgroup_subsys_state *new_css, |
172 | struct cgroup_taskset *tset) | |
dc52ddc0 | 173 | { |
eb95419b | 174 | struct freezer *freezer = css_freezer(new_css); |
bb9d97b6 | 175 | struct task_struct *task; |
ef9fe980 | 176 | bool clear_frozen = false; |
957a4eea | 177 | |
8755ade6 TH |
178 | spin_lock_irq(&freezer->lock); |
179 | ||
80a6a2cf | 180 | /* |
eb95419b | 181 | * Make the new tasks conform to the current state of @new_css. |
8755ade6 TH |
182 | * For simplicity, when migrating any task to a FROZEN cgroup, we |
183 | * revert it to FREEZING and let update_if_frozen() determine the | |
184 | * correct state later. | |
185 | * | |
eb95419b | 186 | * Tasks in @tset are on @new_css but may not conform to its |
8755ade6 TH |
187 | * current state before executing the following - !frozen tasks may |
188 | * be visible in a FROZEN cgroup and frozen tasks in a THAWED one. | |
80a6a2cf | 189 | */ |
d99c8727 | 190 | cgroup_taskset_for_each(task, new_css, tset) { |
d6a2fe13 | 191 | if (!(freezer->state & CGROUP_FREEZING)) { |
8755ade6 TH |
192 | __thaw_task(task); |
193 | } else { | |
194 | freeze_task(task); | |
d6a2fe13 | 195 | freezer->state &= ~CGROUP_FROZEN; |
ef9fe980 | 196 | clear_frozen = true; |
8755ade6 TH |
197 | } |
198 | } | |
dc52ddc0 | 199 | |
8755ade6 | 200 | spin_unlock_irq(&freezer->lock); |
ef9fe980 TH |
201 | |
202 | /* | |
203 | * Propagate FROZEN clearing upwards. We may race with | |
204 | * update_if_frozen(), but as long as both work bottom-up, either | |
205 | * update_if_frozen() sees child's FROZEN cleared or we clear the | |
206 | * parent's FROZEN later. No parent w/ !FROZEN children can be | |
207 | * left FROZEN. | |
208 | */ | |
209 | while (clear_frozen && (freezer = parent_freezer(freezer))) { | |
210 | spin_lock_irq(&freezer->lock); | |
211 | freezer->state &= ~CGROUP_FROZEN; | |
212 | clear_frozen = freezer->state & CGROUP_FREEZING; | |
213 | spin_unlock_irq(&freezer->lock); | |
214 | } | |
f780bdb7 BB |
215 | } |
216 | ||
761b3ef5 | 217 | static void freezer_fork(struct task_struct *task) |
dc52ddc0 MH |
218 | { |
219 | struct freezer *freezer; | |
220 | ||
8b46f880 | 221 | rcu_read_lock(); |
dc52ddc0 | 222 | freezer = task_freezer(task); |
dc52ddc0 | 223 | |
3b1b3f6e LZ |
224 | /* |
225 | * The root cgroup is non-freezable, so we can skip the | |
226 | * following check. | |
227 | */ | |
63876986 | 228 | if (!parent_freezer(freezer)) |
5edee61e | 229 | goto out; |
3b1b3f6e | 230 | |
dc52ddc0 | 231 | spin_lock_irq(&freezer->lock); |
d6a2fe13 | 232 | if (freezer->state & CGROUP_FREEZING) |
839e3407 | 233 | freeze_task(task); |
dc52ddc0 | 234 | spin_unlock_irq(&freezer->lock); |
5edee61e TH |
235 | out: |
236 | rcu_read_unlock(); | |
dc52ddc0 MH |
237 | } |
238 | ||
ef9fe980 TH |
239 | /** |
240 | * update_if_frozen - update whether a cgroup finished freezing | |
182446d0 | 241 | * @css: css of interest |
ef9fe980 TH |
242 | * |
243 | * Once FREEZING is initiated, transition to FROZEN is lazily updated by | |
244 | * calling this function. If the current state is FREEZING but not FROZEN, | |
245 | * this function checks whether all tasks of this cgroup and the descendant | |
246 | * cgroups finished freezing and, if so, sets FROZEN. | |
247 | * | |
248 | * The caller is responsible for grabbing RCU read lock and calling | |
249 | * update_if_frozen() on all descendants prior to invoking this function. | |
b4d18311 TH |
250 | * |
251 | * Task states and freezer state might disagree while tasks are being | |
182446d0 | 252 | * migrated into or out of @css, so we can't verify task states against |
ead5c473 | 253 | * @freezer state here. See freezer_attach() for details. |
dc52ddc0 | 254 | */ |
182446d0 | 255 | static void update_if_frozen(struct cgroup_subsys_state *css) |
dc52ddc0 | 256 | { |
182446d0 | 257 | struct freezer *freezer = css_freezer(css); |
492eb21b | 258 | struct cgroup_subsys_state *pos; |
72ec7029 | 259 | struct css_task_iter it; |
dc52ddc0 | 260 | struct task_struct *task; |
b4d18311 | 261 | |
ef9fe980 TH |
262 | WARN_ON_ONCE(!rcu_read_lock_held()); |
263 | ||
264 | spin_lock_irq(&freezer->lock); | |
265 | ||
d6a2fe13 TH |
266 | if (!(freezer->state & CGROUP_FREEZING) || |
267 | (freezer->state & CGROUP_FROZEN)) | |
ef9fe980 TH |
268 | goto out_unlock; |
269 | ||
270 | /* are all (live) children frozen? */ | |
492eb21b TH |
271 | css_for_each_child(pos, css) { |
272 | struct freezer *child = css_freezer(pos); | |
dc52ddc0 | 273 | |
ef9fe980 TH |
274 | if ((child->state & CGROUP_FREEZER_ONLINE) && |
275 | !(child->state & CGROUP_FROZEN)) | |
276 | goto out_unlock; | |
277 | } | |
278 | ||
279 | /* are all tasks frozen? */ | |
72ec7029 | 280 | css_task_iter_start(css, &it); |
b4d18311 | 281 | |
72ec7029 | 282 | while ((task = css_task_iter_next(&it))) { |
3c426d5e | 283 | if (freezing(task)) { |
3c426d5e TH |
284 | /* |
285 | * freezer_should_skip() indicates that the task | |
286 | * should be skipped when determining freezing | |
287 | * completion. Consider it frozen in addition to | |
288 | * the usual frozen condition. | |
289 | */ | |
5d8f72b5 | 290 | if (!frozen(task) && !freezer_should_skip(task)) |
ef9fe980 | 291 | goto out_iter_end; |
3c426d5e | 292 | } |
dc52ddc0 MH |
293 | } |
294 | ||
d6a2fe13 | 295 | freezer->state |= CGROUP_FROZEN; |
ef9fe980 | 296 | out_iter_end: |
72ec7029 | 297 | css_task_iter_end(&it); |
ef9fe980 TH |
298 | out_unlock: |
299 | spin_unlock_irq(&freezer->lock); | |
dc52ddc0 MH |
300 | } |
301 | ||
2da8ca82 | 302 | static int freezer_read(struct seq_file *m, void *v) |
dc52ddc0 | 303 | { |
2da8ca82 | 304 | struct cgroup_subsys_state *css = seq_css(m), *pos; |
dc52ddc0 | 305 | |
ef9fe980 | 306 | rcu_read_lock(); |
dc52ddc0 | 307 | |
ef9fe980 | 308 | /* update states bottom-up */ |
492eb21b TH |
309 | css_for_each_descendant_post(pos, css) |
310 | update_if_frozen(pos); | |
ef9fe980 TH |
311 | |
312 | rcu_read_unlock(); | |
313 | ||
182446d0 | 314 | seq_puts(m, freezer_state_strs(css_freezer(css)->state)); |
dc52ddc0 MH |
315 | seq_putc(m, '\n'); |
316 | return 0; | |
317 | } | |
318 | ||
bcd66c89 | 319 | static void freeze_cgroup(struct freezer *freezer) |
dc52ddc0 | 320 | { |
72ec7029 | 321 | struct css_task_iter it; |
dc52ddc0 | 322 | struct task_struct *task; |
dc52ddc0 | 323 | |
72ec7029 TH |
324 | css_task_iter_start(&freezer->css, &it); |
325 | while ((task = css_task_iter_next(&it))) | |
51f246ed | 326 | freeze_task(task); |
72ec7029 | 327 | css_task_iter_end(&it); |
dc52ddc0 MH |
328 | } |
329 | ||
bcd66c89 | 330 | static void unfreeze_cgroup(struct freezer *freezer) |
dc52ddc0 | 331 | { |
72ec7029 | 332 | struct css_task_iter it; |
dc52ddc0 MH |
333 | struct task_struct *task; |
334 | ||
72ec7029 TH |
335 | css_task_iter_start(&freezer->css, &it); |
336 | while ((task = css_task_iter_next(&it))) | |
a5be2d0d | 337 | __thaw_task(task); |
72ec7029 | 338 | css_task_iter_end(&it); |
dc52ddc0 MH |
339 | } |
340 | ||
04a4ec32 TH |
341 | /** |
342 | * freezer_apply_state - apply state change to a single cgroup_freezer | |
343 | * @freezer: freezer to apply state change to | |
344 | * @freeze: whether to freeze or unfreeze | |
a2252180 TH |
345 | * @state: CGROUP_FREEZING_* flag to set or clear |
346 | * | |
347 | * Set or clear @state on @cgroup according to @freeze, and perform | |
348 | * freezing or thawing as necessary. | |
04a4ec32 | 349 | */ |
a2252180 TH |
350 | static void freezer_apply_state(struct freezer *freezer, bool freeze, |
351 | unsigned int state) | |
dc52ddc0 | 352 | { |
ead5c473 | 353 | /* also synchronizes against task migration, see freezer_attach() */ |
04a4ec32 | 354 | lockdep_assert_held(&freezer->lock); |
51308ee5 | 355 | |
5300a9b3 TH |
356 | if (!(freezer->state & CGROUP_FREEZER_ONLINE)) |
357 | return; | |
358 | ||
04a4ec32 | 359 | if (freeze) { |
d6a2fe13 | 360 | if (!(freezer->state & CGROUP_FREEZING)) |
a3201227 | 361 | atomic_inc(&system_freezing_cnt); |
a2252180 | 362 | freezer->state |= state; |
bcd66c89 | 363 | freeze_cgroup(freezer); |
04a4ec32 | 364 | } else { |
a2252180 TH |
365 | bool was_freezing = freezer->state & CGROUP_FREEZING; |
366 | ||
367 | freezer->state &= ~state; | |
368 | ||
369 | if (!(freezer->state & CGROUP_FREEZING)) { | |
370 | if (was_freezing) | |
371 | atomic_dec(&system_freezing_cnt); | |
372 | freezer->state &= ~CGROUP_FROZEN; | |
373 | unfreeze_cgroup(freezer); | |
374 | } | |
dc52ddc0 | 375 | } |
04a4ec32 | 376 | } |
22b4e111 | 377 | |
04a4ec32 TH |
378 | /** |
379 | * freezer_change_state - change the freezing state of a cgroup_freezer | |
380 | * @freezer: freezer of interest | |
381 | * @freeze: whether to freeze or thaw | |
382 | * | |
ef9fe980 TH |
383 | * Freeze or thaw @freezer according to @freeze. The operations are |
384 | * recursive - all descendants of @freezer will be affected. | |
04a4ec32 TH |
385 | */ |
386 | static void freezer_change_state(struct freezer *freezer, bool freeze) | |
387 | { | |
492eb21b | 388 | struct cgroup_subsys_state *pos; |
ef9fe980 | 389 | |
ef9fe980 TH |
390 | /* |
391 | * Update all its descendants in pre-order traversal. Each | |
392 | * descendant will try to inherit its parent's FREEZING state as | |
393 | * CGROUP_FREEZING_PARENT. | |
394 | */ | |
395 | rcu_read_lock(); | |
492eb21b TH |
396 | css_for_each_descendant_pre(pos, &freezer->css) { |
397 | struct freezer *pos_f = css_freezer(pos); | |
ef9fe980 TH |
398 | struct freezer *parent = parent_freezer(pos_f); |
399 | ||
ef9fe980 | 400 | spin_lock_irq(&pos_f->lock); |
bd8815a6 TH |
401 | |
402 | if (pos_f == freezer) { | |
403 | freezer_apply_state(pos_f, freeze, | |
404 | CGROUP_FREEZING_SELF); | |
405 | } else { | |
406 | /* | |
407 | * Our update to @parent->state is already visible | |
408 | * which is all we need. No need to lock @parent. | |
409 | * For more info on synchronization, see | |
410 | * freezer_post_create(). | |
411 | */ | |
412 | freezer_apply_state(pos_f, | |
413 | parent->state & CGROUP_FREEZING, | |
414 | CGROUP_FREEZING_PARENT); | |
415 | } | |
416 | ||
ef9fe980 TH |
417 | spin_unlock_irq(&pos_f->lock); |
418 | } | |
419 | rcu_read_unlock(); | |
dc52ddc0 MH |
420 | } |
421 | ||
182446d0 | 422 | static int freezer_write(struct cgroup_subsys_state *css, struct cftype *cft, |
dc52ddc0 MH |
423 | const char *buffer) |
424 | { | |
04a4ec32 | 425 | bool freeze; |
dc52ddc0 | 426 | |
d6a2fe13 | 427 | if (strcmp(buffer, freezer_state_strs(0)) == 0) |
04a4ec32 | 428 | freeze = false; |
d6a2fe13 | 429 | else if (strcmp(buffer, freezer_state_strs(CGROUP_FROZEN)) == 0) |
04a4ec32 | 430 | freeze = true; |
dc52ddc0 | 431 | else |
3b1b3f6e | 432 | return -EINVAL; |
dc52ddc0 | 433 | |
182446d0 | 434 | freezer_change_state(css_freezer(css), freeze); |
51f246ed | 435 | return 0; |
dc52ddc0 MH |
436 | } |
437 | ||
182446d0 TH |
438 | static u64 freezer_self_freezing_read(struct cgroup_subsys_state *css, |
439 | struct cftype *cft) | |
a2252180 | 440 | { |
182446d0 | 441 | struct freezer *freezer = css_freezer(css); |
a2252180 TH |
442 | |
443 | return (bool)(freezer->state & CGROUP_FREEZING_SELF); | |
444 | } | |
445 | ||
182446d0 TH |
446 | static u64 freezer_parent_freezing_read(struct cgroup_subsys_state *css, |
447 | struct cftype *cft) | |
a2252180 | 448 | { |
182446d0 | 449 | struct freezer *freezer = css_freezer(css); |
a2252180 TH |
450 | |
451 | return (bool)(freezer->state & CGROUP_FREEZING_PARENT); | |
452 | } | |
453 | ||
dc52ddc0 MH |
454 | static struct cftype files[] = { |
455 | { | |
456 | .name = "state", | |
4baf6e33 | 457 | .flags = CFTYPE_NOT_ON_ROOT, |
2da8ca82 | 458 | .seq_show = freezer_read, |
dc52ddc0 MH |
459 | .write_string = freezer_write, |
460 | }, | |
a2252180 TH |
461 | { |
462 | .name = "self_freezing", | |
463 | .flags = CFTYPE_NOT_ON_ROOT, | |
464 | .read_u64 = freezer_self_freezing_read, | |
465 | }, | |
466 | { | |
467 | .name = "parent_freezing", | |
468 | .flags = CFTYPE_NOT_ON_ROOT, | |
469 | .read_u64 = freezer_parent_freezing_read, | |
470 | }, | |
4baf6e33 | 471 | { } /* terminate */ |
dc52ddc0 MH |
472 | }; |
473 | ||
073219e9 | 474 | struct cgroup_subsys freezer_cgrp_subsys = { |
92fb9748 TH |
475 | .css_alloc = freezer_css_alloc, |
476 | .css_online = freezer_css_online, | |
477 | .css_offline = freezer_css_offline, | |
478 | .css_free = freezer_css_free, | |
8755ade6 | 479 | .attach = freezer_attach, |
dc52ddc0 | 480 | .fork = freezer_fork, |
4baf6e33 | 481 | .base_cftypes = files, |
dc52ddc0 | 482 | }; |