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