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