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_FREEZING
= (1 << 1), /* this freezer is freezing */
27 CGROUP_FROZEN
= (1 << 3), /* this and its descendants frozen */
31 struct cgroup_subsys_state css
;
36 static inline struct freezer
*cgroup_freezer(struct cgroup
*cgroup
)
38 return container_of(cgroup_subsys_state(cgroup
, freezer_subsys_id
),
42 static inline struct freezer
*task_freezer(struct task_struct
*task
)
44 return container_of(task_subsys_state(task
, freezer_subsys_id
),
48 bool cgroup_freezing(struct task_struct
*task
)
53 ret
= task_freezer(task
)->state
& CGROUP_FREEZING
;
60 * cgroups_write_string() limits the size of freezer state strings to
61 * CGROUP_LOCAL_BUFFER_SIZE
63 static const char *freezer_state_strs(unsigned int state
)
65 if (state
& CGROUP_FROZEN
)
67 if (state
& CGROUP_FREEZING
)
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.
77 * (THAWED) --FROZEN--> (FREEZING) --FROZEN--> (FROZEN)
79 * | \_______THAWED_______/ |
80 * \__________________________THAWED____________/
83 struct cgroup_subsys freezer_subsys
;
85 static struct cgroup_subsys_state
*freezer_create(struct cgroup
*cgroup
)
87 struct freezer
*freezer
;
89 freezer
= kzalloc(sizeof(struct freezer
), GFP_KERNEL
);
91 return ERR_PTR(-ENOMEM
);
93 spin_lock_init(&freezer
->lock
);
97 static void freezer_destroy(struct cgroup
*cgroup
)
99 struct freezer
*freezer
= cgroup_freezer(cgroup
);
101 if (freezer
->state
& CGROUP_FREEZING
)
102 atomic_dec(&system_freezing_cnt
);
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.
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.
115 static void freezer_attach(struct cgroup
*new_cgrp
, struct cgroup_taskset
*tset
)
117 struct freezer
*freezer
= cgroup_freezer(new_cgrp
);
118 struct task_struct
*task
;
120 spin_lock_irq(&freezer
->lock
);
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.
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.
132 cgroup_taskset_for_each(task
, new_cgrp
, tset
) {
133 if (!(freezer
->state
& CGROUP_FREEZING
)) {
137 freezer
->state
&= ~CGROUP_FROZEN
;
141 spin_unlock_irq(&freezer
->lock
);
144 static void freezer_fork(struct task_struct
*task
)
146 struct freezer
*freezer
;
149 freezer
= task_freezer(task
);
152 * The root cgroup is non-freezable, so we can skip the
155 if (!freezer
->css
.cgroup
->parent
)
158 spin_lock_irq(&freezer
->lock
);
159 if (freezer
->state
& CGROUP_FREEZING
)
161 spin_unlock_irq(&freezer
->lock
);
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.
170 * Task states and freezer state might disagree while tasks are being
171 * migrated into or out of @cgroup, so we can't verify task states against
172 * @freezer state here. See freezer_attach() for details.
174 static void update_if_frozen(struct freezer
*freezer
)
176 struct cgroup
*cgroup
= freezer
->css
.cgroup
;
177 struct cgroup_iter it
;
178 struct task_struct
*task
;
180 if (!(freezer
->state
& CGROUP_FREEZING
) ||
181 (freezer
->state
& CGROUP_FROZEN
))
184 cgroup_iter_start(cgroup
, &it
);
186 while ((task
= cgroup_iter_next(cgroup
, &it
))) {
187 if (freezing(task
)) {
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.
194 if (!frozen(task
) && !freezer_should_skip(task
))
199 freezer
->state
|= CGROUP_FROZEN
;
201 cgroup_iter_end(cgroup
, &it
);
204 static int freezer_read(struct cgroup
*cgroup
, struct cftype
*cft
,
207 struct freezer
*freezer
= cgroup_freezer(cgroup
);
210 spin_lock_irq(&freezer
->lock
);
211 update_if_frozen(freezer
);
212 state
= freezer
->state
;
213 spin_unlock_irq(&freezer
->lock
);
215 seq_puts(m
, freezer_state_strs(state
));
220 static void freeze_cgroup(struct freezer
*freezer
)
222 struct cgroup
*cgroup
= freezer
->css
.cgroup
;
223 struct cgroup_iter it
;
224 struct task_struct
*task
;
226 cgroup_iter_start(cgroup
, &it
);
227 while ((task
= cgroup_iter_next(cgroup
, &it
)))
229 cgroup_iter_end(cgroup
, &it
);
232 static void unfreeze_cgroup(struct freezer
*freezer
)
234 struct cgroup
*cgroup
= freezer
->css
.cgroup
;
235 struct cgroup_iter it
;
236 struct task_struct
*task
;
238 cgroup_iter_start(cgroup
, &it
);
239 while ((task
= cgroup_iter_next(cgroup
, &it
)))
241 cgroup_iter_end(cgroup
, &it
);
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
249 static void freezer_apply_state(struct freezer
*freezer
, bool freeze
)
251 /* also synchronizes against task migration, see freezer_attach() */
252 lockdep_assert_held(&freezer
->lock
);
255 if (!(freezer
->state
& CGROUP_FREEZING
))
256 atomic_inc(&system_freezing_cnt
);
257 freezer
->state
|= CGROUP_FREEZING
;
258 freeze_cgroup(freezer
);
260 if (freezer
->state
& CGROUP_FREEZING
)
261 atomic_dec(&system_freezing_cnt
);
262 freezer
->state
&= ~(CGROUP_FREEZING
| CGROUP_FROZEN
);
263 unfreeze_cgroup(freezer
);
268 * freezer_change_state - change the freezing state of a cgroup_freezer
269 * @freezer: freezer of interest
270 * @freeze: whether to freeze or thaw
272 * Freeze or thaw @cgroup according to @freeze.
274 static void freezer_change_state(struct freezer
*freezer
, bool freeze
)
276 /* update @freezer */
277 spin_lock_irq(&freezer
->lock
);
278 freezer_apply_state(freezer
, freeze
);
279 spin_unlock_irq(&freezer
->lock
);
282 static int freezer_write(struct cgroup
*cgroup
, struct cftype
*cft
,
287 if (strcmp(buffer
, freezer_state_strs(0)) == 0)
289 else if (strcmp(buffer
, freezer_state_strs(CGROUP_FROZEN
)) == 0)
294 freezer_change_state(cgroup_freezer(cgroup
), freeze
);
298 static struct cftype files
[] = {
301 .flags
= CFTYPE_NOT_ON_ROOT
,
302 .read_seq_string
= freezer_read
,
303 .write_string
= freezer_write
,
308 struct cgroup_subsys freezer_subsys
= {
310 .create
= freezer_create
,
311 .destroy
= freezer_destroy
,
312 .subsys_id
= freezer_subsys_id
,
313 .attach
= freezer_attach
,
314 .fork
= freezer_fork
,
315 .base_cftypes
= files
,
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
323 .broken_hierarchy
= true,