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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 | ||
d6a2fe13 | 25 | enum freezer_state_flags { |
5300a9b3 | 26 | CGROUP_FREEZER_ONLINE = (1 << 0), /* freezer is fully online */ |
a2252180 TH |
27 | CGROUP_FREEZING_SELF = (1 << 1), /* this freezer is freezing */ |
28 | CGROUP_FREEZING_PARENT = (1 << 2), /* the parent freezer is freezing */ | |
d6a2fe13 | 29 | CGROUP_FROZEN = (1 << 3), /* this and its descendants frozen */ |
a2252180 TH |
30 | |
31 | /* mask for all FREEZING flags */ | |
32 | CGROUP_FREEZING = CGROUP_FREEZING_SELF | CGROUP_FREEZING_PARENT, | |
dc52ddc0 MH |
33 | }; |
34 | ||
35 | struct freezer { | |
bcd66c89 | 36 | struct cgroup_subsys_state css; |
d6a2fe13 | 37 | unsigned int state; |
bcd66c89 | 38 | spinlock_t lock; |
dc52ddc0 MH |
39 | }; |
40 | ||
bcd66c89 | 41 | static inline struct freezer *cgroup_freezer(struct cgroup *cgroup) |
dc52ddc0 | 42 | { |
bcd66c89 TH |
43 | return container_of(cgroup_subsys_state(cgroup, freezer_subsys_id), |
44 | struct freezer, css); | |
dc52ddc0 MH |
45 | } |
46 | ||
47 | static inline struct freezer *task_freezer(struct task_struct *task) | |
48 | { | |
49 | return container_of(task_subsys_state(task, freezer_subsys_id), | |
50 | struct freezer, css); | |
51 | } | |
52 | ||
22b4e111 | 53 | bool cgroup_freezing(struct task_struct *task) |
dc52ddc0 | 54 | { |
22b4e111 | 55 | bool ret; |
dc52ddc0 | 56 | |
22b4e111 | 57 | rcu_read_lock(); |
d6a2fe13 | 58 | ret = task_freezer(task)->state & CGROUP_FREEZING; |
22b4e111 TH |
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 | */ | |
d6a2fe13 TH |
68 | static const char *freezer_state_strs(unsigned int state) |
69 | { | |
70 | if (state & CGROUP_FROZEN) | |
71 | return "FROZEN"; | |
72 | if (state & CGROUP_FREEZING) | |
73 | return "FREEZING"; | |
74 | return "THAWED"; | |
dc52ddc0 MH |
75 | }; |
76 | ||
77 | /* | |
78 | * State diagram | |
79 | * Transitions are caused by userspace writes to the freezer.state file. | |
80 | * The values in parenthesis are state labels. The rest are edge labels. | |
81 | * | |
81dcf33c MH |
82 | * (THAWED) --FROZEN--> (FREEZING) --FROZEN--> (FROZEN) |
83 | * ^ ^ | | | |
84 | * | \_______THAWED_______/ | | |
85 | * \__________________________THAWED____________/ | |
dc52ddc0 MH |
86 | */ |
87 | ||
88 | struct cgroup_subsys freezer_subsys; | |
89 | ||
761b3ef5 | 90 | static struct cgroup_subsys_state *freezer_create(struct cgroup *cgroup) |
dc52ddc0 MH |
91 | { |
92 | struct freezer *freezer; | |
93 | ||
94 | freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL); | |
95 | if (!freezer) | |
96 | return ERR_PTR(-ENOMEM); | |
97 | ||
98 | spin_lock_init(&freezer->lock); | |
dc52ddc0 MH |
99 | return &freezer->css; |
100 | } | |
101 | ||
5300a9b3 TH |
102 | /** |
103 | * freezer_post_create - commit creation of a freezer cgroup | |
104 | * @cgroup: cgroup being created | |
105 | * | |
106 | * We're committing to creation of @cgroup. Mark it online. | |
107 | */ | |
108 | static void freezer_post_create(struct cgroup *cgroup) | |
dc52ddc0 | 109 | { |
a3201227 TH |
110 | struct freezer *freezer = cgroup_freezer(cgroup); |
111 | ||
5300a9b3 TH |
112 | spin_lock_irq(&freezer->lock); |
113 | freezer->state |= CGROUP_FREEZER_ONLINE; | |
114 | spin_unlock_irq(&freezer->lock); | |
115 | } | |
116 | ||
117 | /** | |
118 | * freezer_pre_destroy - initiate destruction of @cgroup | |
119 | * @cgroup: cgroup being destroyed | |
120 | * | |
121 | * @cgroup is going away. Mark it dead and decrement system_freezing_count | |
122 | * if it was holding one. | |
123 | */ | |
124 | static void freezer_pre_destroy(struct cgroup *cgroup) | |
125 | { | |
126 | struct freezer *freezer = cgroup_freezer(cgroup); | |
127 | ||
128 | spin_lock_irq(&freezer->lock); | |
129 | ||
d6a2fe13 | 130 | if (freezer->state & CGROUP_FREEZING) |
a3201227 | 131 | atomic_dec(&system_freezing_cnt); |
5300a9b3 TH |
132 | |
133 | freezer->state = 0; | |
134 | ||
135 | spin_unlock_irq(&freezer->lock); | |
136 | } | |
137 | ||
138 | static void freezer_destroy(struct cgroup *cgroup) | |
139 | { | |
140 | kfree(cgroup_freezer(cgroup)); | |
dc52ddc0 MH |
141 | } |
142 | ||
957a4eea | 143 | /* |
ead5c473 TH |
144 | * Tasks can be migrated into a different freezer anytime regardless of its |
145 | * current state. freezer_attach() is responsible for making new tasks | |
146 | * conform to the current state. | |
147 | * | |
148 | * Freezer state changes and task migration are synchronized via | |
149 | * @freezer->lock. freezer_attach() makes the new tasks conform to the | |
150 | * current state and all following state changes can see the new tasks. | |
957a4eea | 151 | */ |
8755ade6 | 152 | static void freezer_attach(struct cgroup *new_cgrp, struct cgroup_taskset *tset) |
dc52ddc0 | 153 | { |
8755ade6 | 154 | struct freezer *freezer = cgroup_freezer(new_cgrp); |
bb9d97b6 | 155 | struct task_struct *task; |
957a4eea | 156 | |
8755ade6 TH |
157 | spin_lock_irq(&freezer->lock); |
158 | ||
80a6a2cf | 159 | /* |
8755ade6 TH |
160 | * Make the new tasks conform to the current state of @new_cgrp. |
161 | * For simplicity, when migrating any task to a FROZEN cgroup, we | |
162 | * revert it to FREEZING and let update_if_frozen() determine the | |
163 | * correct state later. | |
164 | * | |
165 | * Tasks in @tset are on @new_cgrp but may not conform to its | |
166 | * current state before executing the following - !frozen tasks may | |
167 | * be visible in a FROZEN cgroup and frozen tasks in a THAWED one. | |
80a6a2cf | 168 | */ |
8755ade6 | 169 | cgroup_taskset_for_each(task, new_cgrp, tset) { |
d6a2fe13 | 170 | if (!(freezer->state & CGROUP_FREEZING)) { |
8755ade6 TH |
171 | __thaw_task(task); |
172 | } else { | |
173 | freeze_task(task); | |
d6a2fe13 | 174 | freezer->state &= ~CGROUP_FROZEN; |
8755ade6 TH |
175 | } |
176 | } | |
dc52ddc0 | 177 | |
8755ade6 | 178 | spin_unlock_irq(&freezer->lock); |
f780bdb7 BB |
179 | } |
180 | ||
761b3ef5 | 181 | static void freezer_fork(struct task_struct *task) |
dc52ddc0 MH |
182 | { |
183 | struct freezer *freezer; | |
184 | ||
8b46f880 | 185 | rcu_read_lock(); |
dc52ddc0 | 186 | freezer = task_freezer(task); |
dc52ddc0 | 187 | |
3b1b3f6e LZ |
188 | /* |
189 | * The root cgroup is non-freezable, so we can skip the | |
190 | * following check. | |
191 | */ | |
192 | if (!freezer->css.cgroup->parent) | |
5edee61e | 193 | goto out; |
3b1b3f6e | 194 | |
dc52ddc0 | 195 | spin_lock_irq(&freezer->lock); |
d6a2fe13 | 196 | if (freezer->state & CGROUP_FREEZING) |
839e3407 | 197 | freeze_task(task); |
dc52ddc0 | 198 | spin_unlock_irq(&freezer->lock); |
5edee61e TH |
199 | out: |
200 | rcu_read_unlock(); | |
dc52ddc0 MH |
201 | } |
202 | ||
203 | /* | |
b4d18311 TH |
204 | * We change from FREEZING to FROZEN lazily if the cgroup was only |
205 | * partially frozen when we exitted write. Caller must hold freezer->lock. | |
206 | * | |
207 | * Task states and freezer state might disagree while tasks are being | |
ead5c473 TH |
208 | * migrated into or out of @cgroup, so we can't verify task states against |
209 | * @freezer state here. See freezer_attach() for details. | |
dc52ddc0 | 210 | */ |
bcd66c89 | 211 | static void update_if_frozen(struct freezer *freezer) |
dc52ddc0 | 212 | { |
bcd66c89 | 213 | struct cgroup *cgroup = freezer->css.cgroup; |
dc52ddc0 MH |
214 | struct cgroup_iter it; |
215 | struct task_struct *task; | |
b4d18311 | 216 | |
d6a2fe13 TH |
217 | if (!(freezer->state & CGROUP_FREEZING) || |
218 | (freezer->state & CGROUP_FROZEN)) | |
b4d18311 | 219 | return; |
dc52ddc0 MH |
220 | |
221 | cgroup_iter_start(cgroup, &it); | |
b4d18311 | 222 | |
dc52ddc0 | 223 | while ((task = cgroup_iter_next(cgroup, &it))) { |
3c426d5e | 224 | if (freezing(task)) { |
3c426d5e TH |
225 | /* |
226 | * freezer_should_skip() indicates that the task | |
227 | * should be skipped when determining freezing | |
228 | * completion. Consider it frozen in addition to | |
229 | * the usual frozen condition. | |
230 | */ | |
5d8f72b5 | 231 | if (!frozen(task) && !freezer_should_skip(task)) |
b4d18311 | 232 | goto notyet; |
3c426d5e | 233 | } |
dc52ddc0 MH |
234 | } |
235 | ||
d6a2fe13 | 236 | freezer->state |= CGROUP_FROZEN; |
b4d18311 | 237 | notyet: |
dc52ddc0 MH |
238 | cgroup_iter_end(cgroup, &it); |
239 | } | |
240 | ||
241 | static int freezer_read(struct cgroup *cgroup, struct cftype *cft, | |
242 | struct seq_file *m) | |
243 | { | |
bcd66c89 | 244 | struct freezer *freezer = cgroup_freezer(cgroup); |
d6a2fe13 | 245 | unsigned int state; |
dc52ddc0 | 246 | |
dc52ddc0 | 247 | spin_lock_irq(&freezer->lock); |
bcd66c89 | 248 | update_if_frozen(freezer); |
dc52ddc0 | 249 | state = freezer->state; |
dc52ddc0 | 250 | spin_unlock_irq(&freezer->lock); |
dc52ddc0 | 251 | |
d6a2fe13 | 252 | seq_puts(m, freezer_state_strs(state)); |
dc52ddc0 MH |
253 | seq_putc(m, '\n'); |
254 | return 0; | |
255 | } | |
256 | ||
bcd66c89 | 257 | static void freeze_cgroup(struct freezer *freezer) |
dc52ddc0 | 258 | { |
bcd66c89 | 259 | struct cgroup *cgroup = freezer->css.cgroup; |
dc52ddc0 MH |
260 | struct cgroup_iter it; |
261 | struct task_struct *task; | |
dc52ddc0 | 262 | |
dc52ddc0 | 263 | cgroup_iter_start(cgroup, &it); |
51f246ed TH |
264 | while ((task = cgroup_iter_next(cgroup, &it))) |
265 | freeze_task(task); | |
dc52ddc0 | 266 | cgroup_iter_end(cgroup, &it); |
dc52ddc0 MH |
267 | } |
268 | ||
bcd66c89 | 269 | static void unfreeze_cgroup(struct freezer *freezer) |
dc52ddc0 | 270 | { |
bcd66c89 | 271 | struct cgroup *cgroup = freezer->css.cgroup; |
dc52ddc0 MH |
272 | struct cgroup_iter it; |
273 | struct task_struct *task; | |
274 | ||
275 | cgroup_iter_start(cgroup, &it); | |
a5be2d0d TH |
276 | while ((task = cgroup_iter_next(cgroup, &it))) |
277 | __thaw_task(task); | |
dc52ddc0 | 278 | cgroup_iter_end(cgroup, &it); |
dc52ddc0 MH |
279 | } |
280 | ||
04a4ec32 TH |
281 | /** |
282 | * freezer_apply_state - apply state change to a single cgroup_freezer | |
283 | * @freezer: freezer to apply state change to | |
284 | * @freeze: whether to freeze or unfreeze | |
a2252180 TH |
285 | * @state: CGROUP_FREEZING_* flag to set or clear |
286 | * | |
287 | * Set or clear @state on @cgroup according to @freeze, and perform | |
288 | * freezing or thawing as necessary. | |
04a4ec32 | 289 | */ |
a2252180 TH |
290 | static void freezer_apply_state(struct freezer *freezer, bool freeze, |
291 | unsigned int state) | |
dc52ddc0 | 292 | { |
ead5c473 | 293 | /* also synchronizes against task migration, see freezer_attach() */ |
04a4ec32 | 294 | lockdep_assert_held(&freezer->lock); |
51308ee5 | 295 | |
5300a9b3 TH |
296 | if (!(freezer->state & CGROUP_FREEZER_ONLINE)) |
297 | return; | |
298 | ||
04a4ec32 | 299 | if (freeze) { |
d6a2fe13 | 300 | if (!(freezer->state & CGROUP_FREEZING)) |
a3201227 | 301 | atomic_inc(&system_freezing_cnt); |
a2252180 | 302 | freezer->state |= state; |
bcd66c89 | 303 | freeze_cgroup(freezer); |
04a4ec32 | 304 | } else { |
a2252180 TH |
305 | bool was_freezing = freezer->state & CGROUP_FREEZING; |
306 | ||
307 | freezer->state &= ~state; | |
308 | ||
309 | if (!(freezer->state & CGROUP_FREEZING)) { | |
310 | if (was_freezing) | |
311 | atomic_dec(&system_freezing_cnt); | |
312 | freezer->state &= ~CGROUP_FROZEN; | |
313 | unfreeze_cgroup(freezer); | |
314 | } | |
dc52ddc0 | 315 | } |
04a4ec32 | 316 | } |
22b4e111 | 317 | |
04a4ec32 TH |
318 | /** |
319 | * freezer_change_state - change the freezing state of a cgroup_freezer | |
320 | * @freezer: freezer of interest | |
321 | * @freeze: whether to freeze or thaw | |
322 | * | |
323 | * Freeze or thaw @cgroup according to @freeze. | |
324 | */ | |
325 | static void freezer_change_state(struct freezer *freezer, bool freeze) | |
326 | { | |
327 | /* update @freezer */ | |
328 | spin_lock_irq(&freezer->lock); | |
a2252180 | 329 | freezer_apply_state(freezer, freeze, CGROUP_FREEZING_SELF); |
dc52ddc0 | 330 | spin_unlock_irq(&freezer->lock); |
dc52ddc0 MH |
331 | } |
332 | ||
bcd66c89 | 333 | static int freezer_write(struct cgroup *cgroup, struct cftype *cft, |
dc52ddc0 MH |
334 | const char *buffer) |
335 | { | |
04a4ec32 | 336 | bool freeze; |
dc52ddc0 | 337 | |
d6a2fe13 | 338 | if (strcmp(buffer, freezer_state_strs(0)) == 0) |
04a4ec32 | 339 | freeze = false; |
d6a2fe13 | 340 | else if (strcmp(buffer, freezer_state_strs(CGROUP_FROZEN)) == 0) |
04a4ec32 | 341 | freeze = true; |
dc52ddc0 | 342 | else |
3b1b3f6e | 343 | return -EINVAL; |
dc52ddc0 | 344 | |
04a4ec32 | 345 | freezer_change_state(cgroup_freezer(cgroup), freeze); |
51f246ed | 346 | return 0; |
dc52ddc0 MH |
347 | } |
348 | ||
a2252180 TH |
349 | static u64 freezer_self_freezing_read(struct cgroup *cgroup, struct cftype *cft) |
350 | { | |
351 | struct freezer *freezer = cgroup_freezer(cgroup); | |
352 | ||
353 | return (bool)(freezer->state & CGROUP_FREEZING_SELF); | |
354 | } | |
355 | ||
356 | static u64 freezer_parent_freezing_read(struct cgroup *cgroup, struct cftype *cft) | |
357 | { | |
358 | struct freezer *freezer = cgroup_freezer(cgroup); | |
359 | ||
360 | return (bool)(freezer->state & CGROUP_FREEZING_PARENT); | |
361 | } | |
362 | ||
dc52ddc0 MH |
363 | static struct cftype files[] = { |
364 | { | |
365 | .name = "state", | |
4baf6e33 | 366 | .flags = CFTYPE_NOT_ON_ROOT, |
dc52ddc0 MH |
367 | .read_seq_string = freezer_read, |
368 | .write_string = freezer_write, | |
369 | }, | |
a2252180 TH |
370 | { |
371 | .name = "self_freezing", | |
372 | .flags = CFTYPE_NOT_ON_ROOT, | |
373 | .read_u64 = freezer_self_freezing_read, | |
374 | }, | |
375 | { | |
376 | .name = "parent_freezing", | |
377 | .flags = CFTYPE_NOT_ON_ROOT, | |
378 | .read_u64 = freezer_parent_freezing_read, | |
379 | }, | |
4baf6e33 | 380 | { } /* terminate */ |
dc52ddc0 MH |
381 | }; |
382 | ||
dc52ddc0 MH |
383 | struct cgroup_subsys freezer_subsys = { |
384 | .name = "freezer", | |
385 | .create = freezer_create, | |
5300a9b3 TH |
386 | .post_create = freezer_post_create, |
387 | .pre_destroy = freezer_pre_destroy, | |
dc52ddc0 | 388 | .destroy = freezer_destroy, |
dc52ddc0 | 389 | .subsys_id = freezer_subsys_id, |
8755ade6 | 390 | .attach = freezer_attach, |
dc52ddc0 | 391 | .fork = freezer_fork, |
4baf6e33 | 392 | .base_cftypes = files, |
8c7f6edb TH |
393 | |
394 | /* | |
395 | * freezer subsys doesn't handle hierarchy at all. Frozen state | |
396 | * should be inherited through the hierarchy - if a parent is | |
397 | * frozen, all its children should be frozen. Fix it and remove | |
398 | * the following. | |
399 | */ | |
400 | .broken_hierarchy = true, | |
dc52ddc0 | 401 | }; |