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; |
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 |
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(): |
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) |
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) |
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) |
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 | */ | |
761b3ef5 | 131 | static struct cgroup_subsys_state *freezer_create(struct cgroup *cgroup) |
dc52ddc0 MH |
132 | { |
133 | struct freezer *freezer; | |
134 | ||
135 | freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL); | |
136 | if (!freezer) | |
137 | return ERR_PTR(-ENOMEM); | |
138 | ||
139 | spin_lock_init(&freezer->lock); | |
81dcf33c | 140 | freezer->state = CGROUP_THAWED; |
dc52ddc0 MH |
141 | return &freezer->css; |
142 | } | |
143 | ||
761b3ef5 | 144 | static void freezer_destroy(struct cgroup *cgroup) |
dc52ddc0 | 145 | { |
a3201227 TH |
146 | struct freezer *freezer = cgroup_freezer(cgroup); |
147 | ||
148 | if (freezer->state != CGROUP_THAWED) | |
149 | atomic_dec(&system_freezing_cnt); | |
150 | kfree(freezer); | |
dc52ddc0 MH |
151 | } |
152 | ||
957a4eea MH |
153 | /* |
154 | * The call to cgroup_lock() in the freezer.state write method prevents | |
155 | * a write to that file racing against an attach, and hence the | |
156 | * can_attach() result will remain valid until the attach completes. | |
157 | */ | |
761b3ef5 | 158 | static int freezer_can_attach(struct cgroup *new_cgroup, |
2f7ee569 | 159 | struct cgroup_taskset *tset) |
dc52ddc0 MH |
160 | { |
161 | struct freezer *freezer; | |
bb9d97b6 | 162 | struct task_struct *task; |
957a4eea | 163 | |
80a6a2cf LZ |
164 | /* |
165 | * Anything frozen can't move or be moved to/from. | |
80a6a2cf | 166 | */ |
bb9d97b6 TH |
167 | cgroup_taskset_for_each(task, new_cgroup, tset) |
168 | if (cgroup_freezing(task)) | |
169 | return -EBUSY; | |
957a4eea | 170 | |
0bdba580 TB |
171 | freezer = cgroup_freezer(new_cgroup); |
172 | if (freezer->state != CGROUP_THAWED) | |
957a4eea | 173 | return -EBUSY; |
dc52ddc0 | 174 | |
f780bdb7 BB |
175 | return 0; |
176 | } | |
177 | ||
761b3ef5 | 178 | static void freezer_fork(struct task_struct *task) |
dc52ddc0 MH |
179 | { |
180 | struct freezer *freezer; | |
181 | ||
8b46f880 | 182 | rcu_read_lock(); |
dc52ddc0 | 183 | freezer = task_freezer(task); |
dc52ddc0 | 184 | |
3b1b3f6e LZ |
185 | /* |
186 | * The root cgroup is non-freezable, so we can skip the | |
187 | * following check. | |
188 | */ | |
189 | if (!freezer->css.cgroup->parent) | |
5edee61e | 190 | goto out; |
3b1b3f6e | 191 | |
dc52ddc0 | 192 | spin_lock_irq(&freezer->lock); |
7ccb9743 LZ |
193 | BUG_ON(freezer->state == CGROUP_FROZEN); |
194 | ||
81dcf33c MH |
195 | /* Locking avoids race with FREEZING -> THAWED transitions. */ |
196 | if (freezer->state == CGROUP_FREEZING) | |
839e3407 | 197 | freeze_task(task); |
5edee61e | 198 | |
dc52ddc0 | 199 | spin_unlock_irq(&freezer->lock); |
5edee61e TH |
200 | out: |
201 | rcu_read_unlock(); | |
dc52ddc0 MH |
202 | } |
203 | ||
204 | /* | |
205 | * caller must hold freezer->lock | |
206 | */ | |
2d3cbf8b | 207 | static void update_if_frozen(struct cgroup *cgroup, |
1aece348 | 208 | struct freezer *freezer) |
dc52ddc0 MH |
209 | { |
210 | struct cgroup_iter it; | |
211 | struct task_struct *task; | |
212 | unsigned int nfrozen = 0, ntotal = 0; | |
2d3cbf8b | 213 | enum freezer_state old_state = freezer->state; |
dc52ddc0 MH |
214 | |
215 | cgroup_iter_start(cgroup, &it); | |
216 | while ((task = cgroup_iter_next(cgroup, &it))) { | |
3c426d5e TH |
217 | if (freezing(task)) { |
218 | ntotal++; | |
219 | /* | |
220 | * freezer_should_skip() indicates that the task | |
221 | * should be skipped when determining freezing | |
222 | * completion. Consider it frozen in addition to | |
223 | * the usual frozen condition. | |
224 | */ | |
225 | if (frozen(task) || task_is_stopped_or_traced(task) || | |
226 | freezer_should_skip(task)) | |
227 | nfrozen++; | |
228 | } | |
dc52ddc0 MH |
229 | } |
230 | ||
2d3cbf8b TB |
231 | if (old_state == CGROUP_THAWED) { |
232 | BUG_ON(nfrozen > 0); | |
233 | } else if (old_state == CGROUP_FREEZING) { | |
234 | if (nfrozen == ntotal) | |
235 | freezer->state = CGROUP_FROZEN; | |
236 | } else { /* old_state == CGROUP_FROZEN */ | |
237 | BUG_ON(nfrozen != ntotal); | |
238 | } | |
239 | ||
dc52ddc0 MH |
240 | cgroup_iter_end(cgroup, &it); |
241 | } | |
242 | ||
243 | static int freezer_read(struct cgroup *cgroup, struct cftype *cft, | |
244 | struct seq_file *m) | |
245 | { | |
246 | struct freezer *freezer; | |
247 | enum freezer_state state; | |
248 | ||
249 | if (!cgroup_lock_live_group(cgroup)) | |
250 | return -ENODEV; | |
251 | ||
252 | freezer = cgroup_freezer(cgroup); | |
253 | spin_lock_irq(&freezer->lock); | |
254 | state = freezer->state; | |
81dcf33c | 255 | if (state == CGROUP_FREEZING) { |
dc52ddc0 MH |
256 | /* We change from FREEZING to FROZEN lazily if the cgroup was |
257 | * only partially frozen when we exitted write. */ | |
2d3cbf8b | 258 | update_if_frozen(cgroup, freezer); |
dc52ddc0 MH |
259 | state = freezer->state; |
260 | } | |
261 | spin_unlock_irq(&freezer->lock); | |
262 | cgroup_unlock(); | |
263 | ||
264 | seq_puts(m, freezer_state_strs[state]); | |
265 | seq_putc(m, '\n'); | |
266 | return 0; | |
267 | } | |
268 | ||
51f246ed | 269 | static void freeze_cgroup(struct cgroup *cgroup, struct freezer *freezer) |
dc52ddc0 MH |
270 | { |
271 | struct cgroup_iter it; | |
272 | struct task_struct *task; | |
dc52ddc0 | 273 | |
dc52ddc0 | 274 | cgroup_iter_start(cgroup, &it); |
51f246ed TH |
275 | while ((task = cgroup_iter_next(cgroup, &it))) |
276 | freeze_task(task); | |
dc52ddc0 | 277 | cgroup_iter_end(cgroup, &it); |
dc52ddc0 MH |
278 | } |
279 | ||
00c2e63c | 280 | static void unfreeze_cgroup(struct cgroup *cgroup, struct freezer *freezer) |
dc52ddc0 MH |
281 | { |
282 | struct cgroup_iter it; | |
283 | struct task_struct *task; | |
284 | ||
285 | cgroup_iter_start(cgroup, &it); | |
a5be2d0d TH |
286 | while ((task = cgroup_iter_next(cgroup, &it))) |
287 | __thaw_task(task); | |
dc52ddc0 | 288 | cgroup_iter_end(cgroup, &it); |
dc52ddc0 MH |
289 | } |
290 | ||
51f246ed TH |
291 | static void freezer_change_state(struct cgroup *cgroup, |
292 | enum freezer_state goal_state) | |
dc52ddc0 | 293 | { |
51f246ed | 294 | struct freezer *freezer = cgroup_freezer(cgroup); |
51308ee5 | 295 | |
dc52ddc0 | 296 | spin_lock_irq(&freezer->lock); |
51308ee5 | 297 | |
2d3cbf8b | 298 | update_if_frozen(cgroup, freezer); |
51308ee5 LZ |
299 | |
300 | switch (goal_state) { | |
81dcf33c | 301 | case CGROUP_THAWED: |
a3201227 TH |
302 | if (freezer->state != CGROUP_THAWED) |
303 | atomic_dec(&system_freezing_cnt); | |
22b4e111 | 304 | freezer->state = CGROUP_THAWED; |
51308ee5 | 305 | unfreeze_cgroup(cgroup, freezer); |
dc52ddc0 | 306 | break; |
81dcf33c | 307 | case CGROUP_FROZEN: |
a3201227 TH |
308 | if (freezer->state == CGROUP_THAWED) |
309 | atomic_inc(&system_freezing_cnt); | |
22b4e111 | 310 | freezer->state = CGROUP_FREEZING; |
51f246ed | 311 | freeze_cgroup(cgroup, freezer); |
dc52ddc0 MH |
312 | break; |
313 | default: | |
51308ee5 | 314 | BUG(); |
dc52ddc0 | 315 | } |
22b4e111 | 316 | |
dc52ddc0 | 317 | spin_unlock_irq(&freezer->lock); |
dc52ddc0 MH |
318 | } |
319 | ||
320 | static int freezer_write(struct cgroup *cgroup, | |
321 | struct cftype *cft, | |
322 | const char *buffer) | |
323 | { | |
dc52ddc0 MH |
324 | enum freezer_state goal_state; |
325 | ||
81dcf33c MH |
326 | if (strcmp(buffer, freezer_state_strs[CGROUP_THAWED]) == 0) |
327 | goal_state = CGROUP_THAWED; | |
328 | else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0) | |
329 | goal_state = CGROUP_FROZEN; | |
dc52ddc0 | 330 | else |
3b1b3f6e | 331 | return -EINVAL; |
dc52ddc0 MH |
332 | |
333 | if (!cgroup_lock_live_group(cgroup)) | |
334 | return -ENODEV; | |
51f246ed | 335 | freezer_change_state(cgroup, goal_state); |
dc52ddc0 | 336 | cgroup_unlock(); |
51f246ed | 337 | return 0; |
dc52ddc0 MH |
338 | } |
339 | ||
340 | static struct cftype files[] = { | |
341 | { | |
342 | .name = "state", | |
4baf6e33 | 343 | .flags = CFTYPE_NOT_ON_ROOT, |
dc52ddc0 MH |
344 | .read_seq_string = freezer_read, |
345 | .write_string = freezer_write, | |
346 | }, | |
4baf6e33 | 347 | { } /* terminate */ |
dc52ddc0 MH |
348 | }; |
349 | ||
dc52ddc0 MH |
350 | struct cgroup_subsys freezer_subsys = { |
351 | .name = "freezer", | |
352 | .create = freezer_create, | |
353 | .destroy = freezer_destroy, | |
dc52ddc0 MH |
354 | .subsys_id = freezer_subsys_id, |
355 | .can_attach = freezer_can_attach, | |
dc52ddc0 | 356 | .fork = freezer_fork, |
4baf6e33 | 357 | .base_cftypes = files, |
8c7f6edb TH |
358 | |
359 | /* | |
360 | * freezer subsys doesn't handle hierarchy at all. Frozen state | |
361 | * should be inherited through the hierarchy - if a parent is | |
362 | * frozen, all its children should be frozen. Fix it and remove | |
363 | * the following. | |
364 | */ | |
365 | .broken_hierarchy = true, | |
dc52ddc0 | 366 | }; |