Commit | Line | Data |
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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 { |
a2252180 TH |
26 | CGROUP_FREEZING_SELF = (1 << 1), /* this freezer is freezing */ |
27 | CGROUP_FREEZING_PARENT = (1 << 2), /* the parent freezer is freezing */ | |
d6a2fe13 | 28 | CGROUP_FROZEN = (1 << 3), /* this and its descendants frozen */ |
a2252180 TH |
29 | |
30 | /* mask for all FREEZING flags */ | |
31 | CGROUP_FREEZING = CGROUP_FREEZING_SELF | CGROUP_FREEZING_PARENT, | |
dc52ddc0 MH |
32 | }; |
33 | ||
34 | struct freezer { | |
bcd66c89 | 35 | struct cgroup_subsys_state css; |
d6a2fe13 | 36 | unsigned int state; |
bcd66c89 | 37 | spinlock_t lock; |
dc52ddc0 MH |
38 | }; |
39 | ||
bcd66c89 | 40 | static inline struct freezer *cgroup_freezer(struct cgroup *cgroup) |
dc52ddc0 | 41 | { |
bcd66c89 TH |
42 | return container_of(cgroup_subsys_state(cgroup, freezer_subsys_id), |
43 | struct freezer, css); | |
dc52ddc0 MH |
44 | } |
45 | ||
46 | static inline struct freezer *task_freezer(struct task_struct *task) | |
47 | { | |
48 | return container_of(task_subsys_state(task, freezer_subsys_id), | |
49 | struct freezer, css); | |
50 | } | |
51 | ||
22b4e111 | 52 | bool cgroup_freezing(struct task_struct *task) |
dc52ddc0 | 53 | { |
22b4e111 | 54 | bool ret; |
dc52ddc0 | 55 | |
22b4e111 | 56 | rcu_read_lock(); |
d6a2fe13 | 57 | ret = task_freezer(task)->state & CGROUP_FREEZING; |
22b4e111 TH |
58 | rcu_read_unlock(); |
59 | ||
60 | return ret; | |
dc52ddc0 MH |
61 | } |
62 | ||
63 | /* | |
64 | * cgroups_write_string() limits the size of freezer state strings to | |
65 | * CGROUP_LOCAL_BUFFER_SIZE | |
66 | */ | |
d6a2fe13 TH |
67 | static const char *freezer_state_strs(unsigned int state) |
68 | { | |
69 | if (state & CGROUP_FROZEN) | |
70 | return "FROZEN"; | |
71 | if (state & CGROUP_FREEZING) | |
72 | return "FREEZING"; | |
73 | return "THAWED"; | |
dc52ddc0 MH |
74 | }; |
75 | ||
76 | /* | |
77 | * State diagram | |
78 | * Transitions are caused by userspace writes to the freezer.state file. | |
79 | * The values in parenthesis are state labels. The rest are edge labels. | |
80 | * | |
81dcf33c MH |
81 | * (THAWED) --FROZEN--> (FREEZING) --FROZEN--> (FROZEN) |
82 | * ^ ^ | | | |
83 | * | \_______THAWED_______/ | | |
84 | * \__________________________THAWED____________/ | |
dc52ddc0 MH |
85 | */ |
86 | ||
87 | struct cgroup_subsys freezer_subsys; | |
88 | ||
761b3ef5 | 89 | static struct cgroup_subsys_state *freezer_create(struct cgroup *cgroup) |
dc52ddc0 MH |
90 | { |
91 | struct freezer *freezer; | |
92 | ||
93 | freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL); | |
94 | if (!freezer) | |
95 | return ERR_PTR(-ENOMEM); | |
96 | ||
97 | spin_lock_init(&freezer->lock); | |
dc52ddc0 MH |
98 | return &freezer->css; |
99 | } | |
100 | ||
761b3ef5 | 101 | static void freezer_destroy(struct cgroup *cgroup) |
dc52ddc0 | 102 | { |
a3201227 TH |
103 | struct freezer *freezer = cgroup_freezer(cgroup); |
104 | ||
d6a2fe13 | 105 | if (freezer->state & CGROUP_FREEZING) |
a3201227 TH |
106 | atomic_dec(&system_freezing_cnt); |
107 | kfree(freezer); | |
dc52ddc0 MH |
108 | } |
109 | ||
957a4eea | 110 | /* |
ead5c473 TH |
111 | * Tasks can be migrated into a different freezer anytime regardless of its |
112 | * current state. freezer_attach() is responsible for making new tasks | |
113 | * conform to the current state. | |
114 | * | |
115 | * Freezer state changes and task migration are synchronized via | |
116 | * @freezer->lock. freezer_attach() makes the new tasks conform to the | |
117 | * current state and all following state changes can see the new tasks. | |
957a4eea | 118 | */ |
8755ade6 | 119 | static void freezer_attach(struct cgroup *new_cgrp, struct cgroup_taskset *tset) |
dc52ddc0 | 120 | { |
8755ade6 | 121 | struct freezer *freezer = cgroup_freezer(new_cgrp); |
bb9d97b6 | 122 | struct task_struct *task; |
957a4eea | 123 | |
8755ade6 TH |
124 | spin_lock_irq(&freezer->lock); |
125 | ||
80a6a2cf | 126 | /* |
8755ade6 TH |
127 | * Make the new tasks conform to the current state of @new_cgrp. |
128 | * For simplicity, when migrating any task to a FROZEN cgroup, we | |
129 | * revert it to FREEZING and let update_if_frozen() determine the | |
130 | * correct state later. | |
131 | * | |
132 | * Tasks in @tset are on @new_cgrp but may not conform to its | |
133 | * current state before executing the following - !frozen tasks may | |
134 | * be visible in a FROZEN cgroup and frozen tasks in a THAWED one. | |
80a6a2cf | 135 | */ |
8755ade6 | 136 | cgroup_taskset_for_each(task, new_cgrp, tset) { |
d6a2fe13 | 137 | if (!(freezer->state & CGROUP_FREEZING)) { |
8755ade6 TH |
138 | __thaw_task(task); |
139 | } else { | |
140 | freeze_task(task); | |
d6a2fe13 | 141 | freezer->state &= ~CGROUP_FROZEN; |
8755ade6 TH |
142 | } |
143 | } | |
dc52ddc0 | 144 | |
8755ade6 | 145 | spin_unlock_irq(&freezer->lock); |
f780bdb7 BB |
146 | } |
147 | ||
761b3ef5 | 148 | static void freezer_fork(struct task_struct *task) |
dc52ddc0 MH |
149 | { |
150 | struct freezer *freezer; | |
151 | ||
8b46f880 | 152 | rcu_read_lock(); |
dc52ddc0 | 153 | freezer = task_freezer(task); |
dc52ddc0 | 154 | |
3b1b3f6e LZ |
155 | /* |
156 | * The root cgroup is non-freezable, so we can skip the | |
157 | * following check. | |
158 | */ | |
159 | if (!freezer->css.cgroup->parent) | |
5edee61e | 160 | goto out; |
3b1b3f6e | 161 | |
dc52ddc0 | 162 | spin_lock_irq(&freezer->lock); |
d6a2fe13 | 163 | if (freezer->state & CGROUP_FREEZING) |
839e3407 | 164 | freeze_task(task); |
dc52ddc0 | 165 | spin_unlock_irq(&freezer->lock); |
5edee61e TH |
166 | out: |
167 | rcu_read_unlock(); | |
dc52ddc0 MH |
168 | } |
169 | ||
170 | /* | |
b4d18311 TH |
171 | * We change from FREEZING to FROZEN lazily if the cgroup was only |
172 | * partially frozen when we exitted write. Caller must hold freezer->lock. | |
173 | * | |
174 | * Task states and freezer state might disagree while tasks are being | |
ead5c473 TH |
175 | * migrated into or out of @cgroup, so we can't verify task states against |
176 | * @freezer state here. See freezer_attach() for details. | |
dc52ddc0 | 177 | */ |
bcd66c89 | 178 | static void update_if_frozen(struct freezer *freezer) |
dc52ddc0 | 179 | { |
bcd66c89 | 180 | struct cgroup *cgroup = freezer->css.cgroup; |
dc52ddc0 MH |
181 | struct cgroup_iter it; |
182 | struct task_struct *task; | |
b4d18311 | 183 | |
d6a2fe13 TH |
184 | if (!(freezer->state & CGROUP_FREEZING) || |
185 | (freezer->state & CGROUP_FROZEN)) | |
b4d18311 | 186 | return; |
dc52ddc0 MH |
187 | |
188 | cgroup_iter_start(cgroup, &it); | |
b4d18311 | 189 | |
dc52ddc0 | 190 | while ((task = cgroup_iter_next(cgroup, &it))) { |
3c426d5e | 191 | if (freezing(task)) { |
3c426d5e TH |
192 | /* |
193 | * freezer_should_skip() indicates that the task | |
194 | * should be skipped when determining freezing | |
195 | * completion. Consider it frozen in addition to | |
196 | * the usual frozen condition. | |
197 | */ | |
5d8f72b5 | 198 | if (!frozen(task) && !freezer_should_skip(task)) |
b4d18311 | 199 | goto notyet; |
3c426d5e | 200 | } |
dc52ddc0 MH |
201 | } |
202 | ||
d6a2fe13 | 203 | freezer->state |= CGROUP_FROZEN; |
b4d18311 | 204 | notyet: |
dc52ddc0 MH |
205 | cgroup_iter_end(cgroup, &it); |
206 | } | |
207 | ||
208 | static int freezer_read(struct cgroup *cgroup, struct cftype *cft, | |
209 | struct seq_file *m) | |
210 | { | |
bcd66c89 | 211 | struct freezer *freezer = cgroup_freezer(cgroup); |
d6a2fe13 | 212 | unsigned int state; |
dc52ddc0 | 213 | |
dc52ddc0 | 214 | spin_lock_irq(&freezer->lock); |
bcd66c89 | 215 | update_if_frozen(freezer); |
dc52ddc0 | 216 | state = freezer->state; |
dc52ddc0 | 217 | spin_unlock_irq(&freezer->lock); |
dc52ddc0 | 218 | |
d6a2fe13 | 219 | seq_puts(m, freezer_state_strs(state)); |
dc52ddc0 MH |
220 | seq_putc(m, '\n'); |
221 | return 0; | |
222 | } | |
223 | ||
bcd66c89 | 224 | static void freeze_cgroup(struct freezer *freezer) |
dc52ddc0 | 225 | { |
bcd66c89 | 226 | struct cgroup *cgroup = freezer->css.cgroup; |
dc52ddc0 MH |
227 | struct cgroup_iter it; |
228 | struct task_struct *task; | |
dc52ddc0 | 229 | |
dc52ddc0 | 230 | cgroup_iter_start(cgroup, &it); |
51f246ed TH |
231 | while ((task = cgroup_iter_next(cgroup, &it))) |
232 | freeze_task(task); | |
dc52ddc0 | 233 | cgroup_iter_end(cgroup, &it); |
dc52ddc0 MH |
234 | } |
235 | ||
bcd66c89 | 236 | static void unfreeze_cgroup(struct freezer *freezer) |
dc52ddc0 | 237 | { |
bcd66c89 | 238 | struct cgroup *cgroup = freezer->css.cgroup; |
dc52ddc0 MH |
239 | struct cgroup_iter it; |
240 | struct task_struct *task; | |
241 | ||
242 | cgroup_iter_start(cgroup, &it); | |
a5be2d0d TH |
243 | while ((task = cgroup_iter_next(cgroup, &it))) |
244 | __thaw_task(task); | |
dc52ddc0 | 245 | cgroup_iter_end(cgroup, &it); |
dc52ddc0 MH |
246 | } |
247 | ||
04a4ec32 TH |
248 | /** |
249 | * freezer_apply_state - apply state change to a single cgroup_freezer | |
250 | * @freezer: freezer to apply state change to | |
251 | * @freeze: whether to freeze or unfreeze | |
a2252180 TH |
252 | * @state: CGROUP_FREEZING_* flag to set or clear |
253 | * | |
254 | * Set or clear @state on @cgroup according to @freeze, and perform | |
255 | * freezing or thawing as necessary. | |
04a4ec32 | 256 | */ |
a2252180 TH |
257 | static void freezer_apply_state(struct freezer *freezer, bool freeze, |
258 | unsigned int state) | |
dc52ddc0 | 259 | { |
ead5c473 | 260 | /* also synchronizes against task migration, see freezer_attach() */ |
04a4ec32 | 261 | lockdep_assert_held(&freezer->lock); |
51308ee5 | 262 | |
04a4ec32 | 263 | if (freeze) { |
d6a2fe13 | 264 | if (!(freezer->state & CGROUP_FREEZING)) |
a3201227 | 265 | atomic_inc(&system_freezing_cnt); |
a2252180 | 266 | freezer->state |= state; |
bcd66c89 | 267 | freeze_cgroup(freezer); |
04a4ec32 | 268 | } else { |
a2252180 TH |
269 | bool was_freezing = freezer->state & CGROUP_FREEZING; |
270 | ||
271 | freezer->state &= ~state; | |
272 | ||
273 | if (!(freezer->state & CGROUP_FREEZING)) { | |
274 | if (was_freezing) | |
275 | atomic_dec(&system_freezing_cnt); | |
276 | freezer->state &= ~CGROUP_FROZEN; | |
277 | unfreeze_cgroup(freezer); | |
278 | } | |
dc52ddc0 | 279 | } |
04a4ec32 | 280 | } |
22b4e111 | 281 | |
04a4ec32 TH |
282 | /** |
283 | * freezer_change_state - change the freezing state of a cgroup_freezer | |
284 | * @freezer: freezer of interest | |
285 | * @freeze: whether to freeze or thaw | |
286 | * | |
287 | * Freeze or thaw @cgroup according to @freeze. | |
288 | */ | |
289 | static void freezer_change_state(struct freezer *freezer, bool freeze) | |
290 | { | |
291 | /* update @freezer */ | |
292 | spin_lock_irq(&freezer->lock); | |
a2252180 | 293 | freezer_apply_state(freezer, freeze, CGROUP_FREEZING_SELF); |
dc52ddc0 | 294 | spin_unlock_irq(&freezer->lock); |
dc52ddc0 MH |
295 | } |
296 | ||
bcd66c89 | 297 | static int freezer_write(struct cgroup *cgroup, struct cftype *cft, |
dc52ddc0 MH |
298 | const char *buffer) |
299 | { | |
04a4ec32 | 300 | bool freeze; |
dc52ddc0 | 301 | |
d6a2fe13 | 302 | if (strcmp(buffer, freezer_state_strs(0)) == 0) |
04a4ec32 | 303 | freeze = false; |
d6a2fe13 | 304 | else if (strcmp(buffer, freezer_state_strs(CGROUP_FROZEN)) == 0) |
04a4ec32 | 305 | freeze = true; |
dc52ddc0 | 306 | else |
3b1b3f6e | 307 | return -EINVAL; |
dc52ddc0 | 308 | |
04a4ec32 | 309 | freezer_change_state(cgroup_freezer(cgroup), freeze); |
51f246ed | 310 | return 0; |
dc52ddc0 MH |
311 | } |
312 | ||
a2252180 TH |
313 | static u64 freezer_self_freezing_read(struct cgroup *cgroup, struct cftype *cft) |
314 | { | |
315 | struct freezer *freezer = cgroup_freezer(cgroup); | |
316 | ||
317 | return (bool)(freezer->state & CGROUP_FREEZING_SELF); | |
318 | } | |
319 | ||
320 | static u64 freezer_parent_freezing_read(struct cgroup *cgroup, struct cftype *cft) | |
321 | { | |
322 | struct freezer *freezer = cgroup_freezer(cgroup); | |
323 | ||
324 | return (bool)(freezer->state & CGROUP_FREEZING_PARENT); | |
325 | } | |
326 | ||
dc52ddc0 MH |
327 | static struct cftype files[] = { |
328 | { | |
329 | .name = "state", | |
4baf6e33 | 330 | .flags = CFTYPE_NOT_ON_ROOT, |
dc52ddc0 MH |
331 | .read_seq_string = freezer_read, |
332 | .write_string = freezer_write, | |
333 | }, | |
a2252180 TH |
334 | { |
335 | .name = "self_freezing", | |
336 | .flags = CFTYPE_NOT_ON_ROOT, | |
337 | .read_u64 = freezer_self_freezing_read, | |
338 | }, | |
339 | { | |
340 | .name = "parent_freezing", | |
341 | .flags = CFTYPE_NOT_ON_ROOT, | |
342 | .read_u64 = freezer_parent_freezing_read, | |
343 | }, | |
4baf6e33 | 344 | { } /* terminate */ |
dc52ddc0 MH |
345 | }; |
346 | ||
dc52ddc0 MH |
347 | struct cgroup_subsys freezer_subsys = { |
348 | .name = "freezer", | |
349 | .create = freezer_create, | |
350 | .destroy = freezer_destroy, | |
dc52ddc0 | 351 | .subsys_id = freezer_subsys_id, |
8755ade6 | 352 | .attach = freezer_attach, |
dc52ddc0 | 353 | .fork = freezer_fork, |
4baf6e33 | 354 | .base_cftypes = files, |
8c7f6edb TH |
355 | |
356 | /* | |
357 | * freezer subsys doesn't handle hierarchy at all. Frozen state | |
358 | * should be inherited through the hierarchy - if a parent is | |
359 | * frozen, all its children should be frozen. Fix it and remove | |
360 | * the following. | |
361 | */ | |
362 | .broken_hierarchy = true, | |
dc52ddc0 | 363 | }; |