2 * cgroup_freezer.c - control group freezer subsystem
4 * Copyright IBM Corporation, 2007
6 * Author : Cedric Le Goater <clg@fr.ibm.com>
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.
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.
17 #include <linux/export.h>
18 #include <linux/slab.h>
19 #include <linux/cgroup.h>
21 #include <linux/uaccess.h>
22 #include <linux/freezer.h>
23 #include <linux/seq_file.h>
25 enum freezer_state_flags
{
26 CGROUP_FREEZER_ONLINE
= (1 << 0), /* freezer is fully online */
27 CGROUP_FREEZING_SELF
= (1 << 1), /* this freezer is freezing */
28 CGROUP_FREEZING_PARENT
= (1 << 2), /* the parent freezer is freezing */
29 CGROUP_FROZEN
= (1 << 3), /* this and its descendants frozen */
31 /* mask for all FREEZING flags */
32 CGROUP_FREEZING
= CGROUP_FREEZING_SELF
| CGROUP_FREEZING_PARENT
,
36 struct cgroup_subsys_state css
;
41 static inline struct freezer
*cgroup_freezer(struct cgroup
*cgroup
)
43 return container_of(cgroup_subsys_state(cgroup
, freezer_subsys_id
),
47 static inline struct freezer
*task_freezer(struct task_struct
*task
)
49 return container_of(task_subsys_state(task
, freezer_subsys_id
),
53 bool cgroup_freezing(struct task_struct
*task
)
58 ret
= task_freezer(task
)->state
& CGROUP_FREEZING
;
65 * cgroups_write_string() limits the size of freezer state strings to
66 * CGROUP_LOCAL_BUFFER_SIZE
68 static const char *freezer_state_strs(unsigned int state
)
70 if (state
& CGROUP_FROZEN
)
72 if (state
& CGROUP_FREEZING
)
79 * Transitions are caused by userspace writes to the freezer.state file.
80 * The values in parenthesis are state labels. The rest are edge labels.
82 * (THAWED) --FROZEN--> (FREEZING) --FROZEN--> (FROZEN)
84 * | \_______THAWED_______/ |
85 * \__________________________THAWED____________/
88 struct cgroup_subsys freezer_subsys
;
90 static struct cgroup_subsys_state
*freezer_create(struct cgroup
*cgroup
)
92 struct freezer
*freezer
;
94 freezer
= kzalloc(sizeof(struct freezer
), GFP_KERNEL
);
96 return ERR_PTR(-ENOMEM
);
98 spin_lock_init(&freezer
->lock
);
103 * freezer_post_create - commit creation of a freezer cgroup
104 * @cgroup: cgroup being created
106 * We're committing to creation of @cgroup. Mark it online.
108 static void freezer_post_create(struct cgroup
*cgroup
)
110 struct freezer
*freezer
= cgroup_freezer(cgroup
);
112 spin_lock_irq(&freezer
->lock
);
113 freezer
->state
|= CGROUP_FREEZER_ONLINE
;
114 spin_unlock_irq(&freezer
->lock
);
118 * freezer_pre_destroy - initiate destruction of @cgroup
119 * @cgroup: cgroup being destroyed
121 * @cgroup is going away. Mark it dead and decrement system_freezing_count
122 * if it was holding one.
124 static void freezer_pre_destroy(struct cgroup
*cgroup
)
126 struct freezer
*freezer
= cgroup_freezer(cgroup
);
128 spin_lock_irq(&freezer
->lock
);
130 if (freezer
->state
& CGROUP_FREEZING
)
131 atomic_dec(&system_freezing_cnt
);
135 spin_unlock_irq(&freezer
->lock
);
138 static void freezer_destroy(struct cgroup
*cgroup
)
140 kfree(cgroup_freezer(cgroup
));
144 * Tasks can be migrated into a different freezer anytime regardless of its
145 * current state. freezer_attach() is responsible for making new tasks
146 * conform to the current state.
148 * Freezer state changes and task migration are synchronized via
149 * @freezer->lock. freezer_attach() makes the new tasks conform to the
150 * current state and all following state changes can see the new tasks.
152 static void freezer_attach(struct cgroup
*new_cgrp
, struct cgroup_taskset
*tset
)
154 struct freezer
*freezer
= cgroup_freezer(new_cgrp
);
155 struct task_struct
*task
;
157 spin_lock_irq(&freezer
->lock
);
160 * Make the new tasks conform to the current state of @new_cgrp.
161 * For simplicity, when migrating any task to a FROZEN cgroup, we
162 * revert it to FREEZING and let update_if_frozen() determine the
163 * correct state later.
165 * Tasks in @tset are on @new_cgrp but may not conform to its
166 * current state before executing the following - !frozen tasks may
167 * be visible in a FROZEN cgroup and frozen tasks in a THAWED one.
169 cgroup_taskset_for_each(task
, new_cgrp
, tset
) {
170 if (!(freezer
->state
& CGROUP_FREEZING
)) {
174 freezer
->state
&= ~CGROUP_FROZEN
;
178 spin_unlock_irq(&freezer
->lock
);
181 static void freezer_fork(struct task_struct
*task
)
183 struct freezer
*freezer
;
186 freezer
= task_freezer(task
);
189 * The root cgroup is non-freezable, so we can skip the
192 if (!freezer
->css
.cgroup
->parent
)
195 spin_lock_irq(&freezer
->lock
);
196 if (freezer
->state
& CGROUP_FREEZING
)
198 spin_unlock_irq(&freezer
->lock
);
204 * We change from FREEZING to FROZEN lazily if the cgroup was only
205 * partially frozen when we exitted write. Caller must hold freezer->lock.
207 * Task states and freezer state might disagree while tasks are being
208 * migrated into or out of @cgroup, so we can't verify task states against
209 * @freezer state here. See freezer_attach() for details.
211 static void update_if_frozen(struct freezer
*freezer
)
213 struct cgroup
*cgroup
= freezer
->css
.cgroup
;
214 struct cgroup_iter it
;
215 struct task_struct
*task
;
217 if (!(freezer
->state
& CGROUP_FREEZING
) ||
218 (freezer
->state
& CGROUP_FROZEN
))
221 cgroup_iter_start(cgroup
, &it
);
223 while ((task
= cgroup_iter_next(cgroup
, &it
))) {
224 if (freezing(task
)) {
226 * freezer_should_skip() indicates that the task
227 * should be skipped when determining freezing
228 * completion. Consider it frozen in addition to
229 * the usual frozen condition.
231 if (!frozen(task
) && !freezer_should_skip(task
))
236 freezer
->state
|= CGROUP_FROZEN
;
238 cgroup_iter_end(cgroup
, &it
);
241 static int freezer_read(struct cgroup
*cgroup
, struct cftype
*cft
,
244 struct freezer
*freezer
= cgroup_freezer(cgroup
);
247 spin_lock_irq(&freezer
->lock
);
248 update_if_frozen(freezer
);
249 state
= freezer
->state
;
250 spin_unlock_irq(&freezer
->lock
);
252 seq_puts(m
, freezer_state_strs(state
));
257 static void freeze_cgroup(struct freezer
*freezer
)
259 struct cgroup
*cgroup
= freezer
->css
.cgroup
;
260 struct cgroup_iter it
;
261 struct task_struct
*task
;
263 cgroup_iter_start(cgroup
, &it
);
264 while ((task
= cgroup_iter_next(cgroup
, &it
)))
266 cgroup_iter_end(cgroup
, &it
);
269 static void unfreeze_cgroup(struct freezer
*freezer
)
271 struct cgroup
*cgroup
= freezer
->css
.cgroup
;
272 struct cgroup_iter it
;
273 struct task_struct
*task
;
275 cgroup_iter_start(cgroup
, &it
);
276 while ((task
= cgroup_iter_next(cgroup
, &it
)))
278 cgroup_iter_end(cgroup
, &it
);
282 * freezer_apply_state - apply state change to a single cgroup_freezer
283 * @freezer: freezer to apply state change to
284 * @freeze: whether to freeze or unfreeze
285 * @state: CGROUP_FREEZING_* flag to set or clear
287 * Set or clear @state on @cgroup according to @freeze, and perform
288 * freezing or thawing as necessary.
290 static void freezer_apply_state(struct freezer
*freezer
, bool freeze
,
293 /* also synchronizes against task migration, see freezer_attach() */
294 lockdep_assert_held(&freezer
->lock
);
296 if (!(freezer
->state
& CGROUP_FREEZER_ONLINE
))
300 if (!(freezer
->state
& CGROUP_FREEZING
))
301 atomic_inc(&system_freezing_cnt
);
302 freezer
->state
|= state
;
303 freeze_cgroup(freezer
);
305 bool was_freezing
= freezer
->state
& CGROUP_FREEZING
;
307 freezer
->state
&= ~state
;
309 if (!(freezer
->state
& CGROUP_FREEZING
)) {
311 atomic_dec(&system_freezing_cnt
);
312 freezer
->state
&= ~CGROUP_FROZEN
;
313 unfreeze_cgroup(freezer
);
319 * freezer_change_state - change the freezing state of a cgroup_freezer
320 * @freezer: freezer of interest
321 * @freeze: whether to freeze or thaw
323 * Freeze or thaw @cgroup according to @freeze.
325 static void freezer_change_state(struct freezer
*freezer
, bool freeze
)
327 /* update @freezer */
328 spin_lock_irq(&freezer
->lock
);
329 freezer_apply_state(freezer
, freeze
, CGROUP_FREEZING_SELF
);
330 spin_unlock_irq(&freezer
->lock
);
333 static int freezer_write(struct cgroup
*cgroup
, struct cftype
*cft
,
338 if (strcmp(buffer
, freezer_state_strs(0)) == 0)
340 else if (strcmp(buffer
, freezer_state_strs(CGROUP_FROZEN
)) == 0)
345 freezer_change_state(cgroup_freezer(cgroup
), freeze
);
349 static u64
freezer_self_freezing_read(struct cgroup
*cgroup
, struct cftype
*cft
)
351 struct freezer
*freezer
= cgroup_freezer(cgroup
);
353 return (bool)(freezer
->state
& CGROUP_FREEZING_SELF
);
356 static u64
freezer_parent_freezing_read(struct cgroup
*cgroup
, struct cftype
*cft
)
358 struct freezer
*freezer
= cgroup_freezer(cgroup
);
360 return (bool)(freezer
->state
& CGROUP_FREEZING_PARENT
);
363 static struct cftype files
[] = {
366 .flags
= CFTYPE_NOT_ON_ROOT
,
367 .read_seq_string
= freezer_read
,
368 .write_string
= freezer_write
,
371 .name
= "self_freezing",
372 .flags
= CFTYPE_NOT_ON_ROOT
,
373 .read_u64
= freezer_self_freezing_read
,
376 .name
= "parent_freezing",
377 .flags
= CFTYPE_NOT_ON_ROOT
,
378 .read_u64
= freezer_parent_freezing_read
,
383 struct cgroup_subsys freezer_subsys
= {
385 .create
= freezer_create
,
386 .post_create
= freezer_post_create
,
387 .pre_destroy
= freezer_pre_destroy
,
388 .destroy
= freezer_destroy
,
389 .subsys_id
= freezer_subsys_id
,
390 .attach
= freezer_attach
,
391 .fork
= freezer_fork
,
392 .base_cftypes
= files
,
395 * freezer subsys doesn't handle hierarchy at all. Frozen state
396 * should be inherited through the hierarchy - if a parent is
397 * frozen, all its children should be frozen. Fix it and remove
400 .broken_hierarchy
= true,