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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 | ||
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 | ||
761b3ef5 | 87 | static struct cgroup_subsys_state *freezer_create(struct cgroup *cgroup) |
dc52ddc0 MH |
88 | { |
89 | struct freezer *freezer; | |
90 | ||
91 | freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL); | |
92 | if (!freezer) | |
93 | return ERR_PTR(-ENOMEM); | |
94 | ||
95 | spin_lock_init(&freezer->lock); | |
81dcf33c | 96 | freezer->state = CGROUP_THAWED; |
dc52ddc0 MH |
97 | return &freezer->css; |
98 | } | |
99 | ||
761b3ef5 | 100 | static void freezer_destroy(struct cgroup *cgroup) |
dc52ddc0 | 101 | { |
a3201227 TH |
102 | struct freezer *freezer = cgroup_freezer(cgroup); |
103 | ||
104 | if (freezer->state != CGROUP_THAWED) | |
105 | atomic_dec(&system_freezing_cnt); | |
106 | kfree(freezer); | |
dc52ddc0 MH |
107 | } |
108 | ||
957a4eea | 109 | /* |
ead5c473 TH |
110 | * Tasks can be migrated into a different freezer anytime regardless of its |
111 | * current state. freezer_attach() is responsible for making new tasks | |
112 | * conform to the current state. | |
113 | * | |
114 | * Freezer state changes and task migration are synchronized via | |
115 | * @freezer->lock. freezer_attach() makes the new tasks conform to the | |
116 | * current state and all following state changes can see the new tasks. | |
957a4eea | 117 | */ |
8755ade6 | 118 | static void freezer_attach(struct cgroup *new_cgrp, struct cgroup_taskset *tset) |
dc52ddc0 | 119 | { |
8755ade6 | 120 | struct freezer *freezer = cgroup_freezer(new_cgrp); |
bb9d97b6 | 121 | struct task_struct *task; |
957a4eea | 122 | |
8755ade6 TH |
123 | spin_lock_irq(&freezer->lock); |
124 | ||
80a6a2cf | 125 | /* |
8755ade6 TH |
126 | * Make the new tasks conform to the current state of @new_cgrp. |
127 | * For simplicity, when migrating any task to a FROZEN cgroup, we | |
128 | * revert it to FREEZING and let update_if_frozen() determine the | |
129 | * correct state later. | |
130 | * | |
131 | * Tasks in @tset are on @new_cgrp but may not conform to its | |
132 | * current state before executing the following - !frozen tasks may | |
133 | * be visible in a FROZEN cgroup and frozen tasks in a THAWED one. | |
134 | * This means that, to determine whether to freeze, one should test | |
135 | * whether the state equals THAWED. | |
80a6a2cf | 136 | */ |
8755ade6 TH |
137 | cgroup_taskset_for_each(task, new_cgrp, tset) { |
138 | if (freezer->state == CGROUP_THAWED) { | |
139 | __thaw_task(task); | |
140 | } else { | |
141 | freeze_task(task); | |
142 | freezer->state = CGROUP_FREEZING; | |
143 | } | |
144 | } | |
dc52ddc0 | 145 | |
8755ade6 | 146 | spin_unlock_irq(&freezer->lock); |
f780bdb7 BB |
147 | } |
148 | ||
761b3ef5 | 149 | static void freezer_fork(struct task_struct *task) |
dc52ddc0 MH |
150 | { |
151 | struct freezer *freezer; | |
152 | ||
8b46f880 | 153 | rcu_read_lock(); |
dc52ddc0 | 154 | freezer = task_freezer(task); |
dc52ddc0 | 155 | |
3b1b3f6e LZ |
156 | /* |
157 | * The root cgroup is non-freezable, so we can skip the | |
158 | * following check. | |
159 | */ | |
160 | if (!freezer->css.cgroup->parent) | |
5edee61e | 161 | goto out; |
3b1b3f6e | 162 | |
dc52ddc0 | 163 | spin_lock_irq(&freezer->lock); |
8755ade6 TH |
164 | /* |
165 | * @task might have been just migrated into a FROZEN cgroup. Test | |
166 | * equality with THAWED. Read the comment in freezer_attach(). | |
167 | */ | |
168 | if (freezer->state != CGROUP_THAWED) | |
839e3407 | 169 | freeze_task(task); |
dc52ddc0 | 170 | spin_unlock_irq(&freezer->lock); |
5edee61e TH |
171 | out: |
172 | rcu_read_unlock(); | |
dc52ddc0 MH |
173 | } |
174 | ||
175 | /* | |
b4d18311 TH |
176 | * We change from FREEZING to FROZEN lazily if the cgroup was only |
177 | * partially frozen when we exitted write. Caller must hold freezer->lock. | |
178 | * | |
179 | * Task states and freezer state might disagree while tasks are being | |
ead5c473 TH |
180 | * migrated into or out of @cgroup, so we can't verify task states against |
181 | * @freezer state here. See freezer_attach() for details. | |
dc52ddc0 | 182 | */ |
b4d18311 | 183 | static void update_if_frozen(struct cgroup *cgroup, struct freezer *freezer) |
dc52ddc0 MH |
184 | { |
185 | struct cgroup_iter it; | |
186 | struct task_struct *task; | |
b4d18311 TH |
187 | |
188 | if (freezer->state != CGROUP_FREEZING) | |
189 | return; | |
dc52ddc0 MH |
190 | |
191 | cgroup_iter_start(cgroup, &it); | |
b4d18311 | 192 | |
dc52ddc0 | 193 | while ((task = cgroup_iter_next(cgroup, &it))) { |
3c426d5e | 194 | if (freezing(task)) { |
3c426d5e TH |
195 | /* |
196 | * freezer_should_skip() indicates that the task | |
197 | * should be skipped when determining freezing | |
198 | * completion. Consider it frozen in addition to | |
199 | * the usual frozen condition. | |
200 | */ | |
b4d18311 TH |
201 | if (!frozen(task) && !task_is_stopped_or_traced(task) && |
202 | !freezer_should_skip(task)) | |
203 | goto notyet; | |
3c426d5e | 204 | } |
dc52ddc0 MH |
205 | } |
206 | ||
b4d18311 TH |
207 | freezer->state = CGROUP_FROZEN; |
208 | notyet: | |
dc52ddc0 MH |
209 | cgroup_iter_end(cgroup, &it); |
210 | } | |
211 | ||
212 | static int freezer_read(struct cgroup *cgroup, struct cftype *cft, | |
213 | struct seq_file *m) | |
214 | { | |
215 | struct freezer *freezer; | |
216 | enum freezer_state state; | |
217 | ||
dc52ddc0 MH |
218 | freezer = cgroup_freezer(cgroup); |
219 | spin_lock_irq(&freezer->lock); | |
b4d18311 | 220 | update_if_frozen(cgroup, freezer); |
dc52ddc0 | 221 | state = freezer->state; |
dc52ddc0 | 222 | spin_unlock_irq(&freezer->lock); |
dc52ddc0 MH |
223 | |
224 | seq_puts(m, freezer_state_strs[state]); | |
225 | seq_putc(m, '\n'); | |
226 | return 0; | |
227 | } | |
228 | ||
51f246ed | 229 | static void freeze_cgroup(struct cgroup *cgroup, struct freezer *freezer) |
dc52ddc0 MH |
230 | { |
231 | struct cgroup_iter it; | |
232 | struct task_struct *task; | |
dc52ddc0 | 233 | |
dc52ddc0 | 234 | cgroup_iter_start(cgroup, &it); |
51f246ed TH |
235 | while ((task = cgroup_iter_next(cgroup, &it))) |
236 | freeze_task(task); | |
dc52ddc0 | 237 | cgroup_iter_end(cgroup, &it); |
dc52ddc0 MH |
238 | } |
239 | ||
00c2e63c | 240 | static void unfreeze_cgroup(struct cgroup *cgroup, struct freezer *freezer) |
dc52ddc0 MH |
241 | { |
242 | struct cgroup_iter it; | |
243 | struct task_struct *task; | |
244 | ||
245 | cgroup_iter_start(cgroup, &it); | |
a5be2d0d TH |
246 | while ((task = cgroup_iter_next(cgroup, &it))) |
247 | __thaw_task(task); | |
dc52ddc0 | 248 | cgroup_iter_end(cgroup, &it); |
dc52ddc0 MH |
249 | } |
250 | ||
51f246ed TH |
251 | static void freezer_change_state(struct cgroup *cgroup, |
252 | enum freezer_state goal_state) | |
dc52ddc0 | 253 | { |
51f246ed | 254 | struct freezer *freezer = cgroup_freezer(cgroup); |
51308ee5 | 255 | |
ead5c473 | 256 | /* also synchronizes against task migration, see freezer_attach() */ |
dc52ddc0 | 257 | spin_lock_irq(&freezer->lock); |
51308ee5 | 258 | |
51308ee5 | 259 | switch (goal_state) { |
81dcf33c | 260 | case CGROUP_THAWED: |
a3201227 TH |
261 | if (freezer->state != CGROUP_THAWED) |
262 | atomic_dec(&system_freezing_cnt); | |
22b4e111 | 263 | freezer->state = CGROUP_THAWED; |
51308ee5 | 264 | unfreeze_cgroup(cgroup, freezer); |
dc52ddc0 | 265 | break; |
81dcf33c | 266 | case CGROUP_FROZEN: |
a3201227 TH |
267 | if (freezer->state == CGROUP_THAWED) |
268 | atomic_inc(&system_freezing_cnt); | |
22b4e111 | 269 | freezer->state = CGROUP_FREEZING; |
51f246ed | 270 | freeze_cgroup(cgroup, freezer); |
dc52ddc0 MH |
271 | break; |
272 | default: | |
51308ee5 | 273 | BUG(); |
dc52ddc0 | 274 | } |
22b4e111 | 275 | |
dc52ddc0 | 276 | spin_unlock_irq(&freezer->lock); |
dc52ddc0 MH |
277 | } |
278 | ||
279 | static int freezer_write(struct cgroup *cgroup, | |
280 | struct cftype *cft, | |
281 | const char *buffer) | |
282 | { | |
dc52ddc0 MH |
283 | enum freezer_state goal_state; |
284 | ||
81dcf33c MH |
285 | if (strcmp(buffer, freezer_state_strs[CGROUP_THAWED]) == 0) |
286 | goal_state = CGROUP_THAWED; | |
287 | else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0) | |
288 | goal_state = CGROUP_FROZEN; | |
dc52ddc0 | 289 | else |
3b1b3f6e | 290 | return -EINVAL; |
dc52ddc0 | 291 | |
51f246ed | 292 | freezer_change_state(cgroup, goal_state); |
51f246ed | 293 | return 0; |
dc52ddc0 MH |
294 | } |
295 | ||
296 | static struct cftype files[] = { | |
297 | { | |
298 | .name = "state", | |
4baf6e33 | 299 | .flags = CFTYPE_NOT_ON_ROOT, |
dc52ddc0 MH |
300 | .read_seq_string = freezer_read, |
301 | .write_string = freezer_write, | |
302 | }, | |
4baf6e33 | 303 | { } /* terminate */ |
dc52ddc0 MH |
304 | }; |
305 | ||
dc52ddc0 MH |
306 | struct cgroup_subsys freezer_subsys = { |
307 | .name = "freezer", | |
308 | .create = freezer_create, | |
309 | .destroy = freezer_destroy, | |
dc52ddc0 | 310 | .subsys_id = freezer_subsys_id, |
8755ade6 | 311 | .attach = freezer_attach, |
dc52ddc0 | 312 | .fork = freezer_fork, |
4baf6e33 | 313 | .base_cftypes = files, |
8c7f6edb TH |
314 | |
315 | /* | |
316 | * freezer subsys doesn't handle hierarchy at all. Frozen state | |
317 | * should be inherited through the hierarchy - if a parent is | |
318 | * frozen, all its children should be frozen. Fix it and remove | |
319 | * the following. | |
320 | */ | |
321 | .broken_hierarchy = true, | |
dc52ddc0 | 322 | }; |