Merge branch 'x86-intel-mid-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[platform/adaptation/renesas_rcar/renesas_kernel.git] / kernel / cgroup_freezer.c
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
17 #include <linux/export.h>
18 #include <linux/slab.h>
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 /*
26  * A cgroup is freezing if any FREEZING flags are set.  FREEZING_SELF is
27  * set if "FROZEN" is written to freezer.state cgroupfs file, and cleared
28  * for "THAWED".  FREEZING_PARENT is set if the parent freezer is FREEZING
29  * for whatever reason.  IOW, a cgroup has FREEZING_PARENT set if one of
30  * its ancestors has FREEZING_SELF set.
31  */
32 enum freezer_state_flags {
33         CGROUP_FREEZER_ONLINE   = (1 << 0), /* freezer is fully online */
34         CGROUP_FREEZING_SELF    = (1 << 1), /* this freezer is freezing */
35         CGROUP_FREEZING_PARENT  = (1 << 2), /* the parent freezer is freezing */
36         CGROUP_FROZEN           = (1 << 3), /* this and its descendants frozen */
37
38         /* mask for all FREEZING flags */
39         CGROUP_FREEZING         = CGROUP_FREEZING_SELF | CGROUP_FREEZING_PARENT,
40 };
41
42 struct freezer {
43         struct cgroup_subsys_state      css;
44         unsigned int                    state;
45         spinlock_t                      lock;
46 };
47
48 static inline struct freezer *css_freezer(struct cgroup_subsys_state *css)
49 {
50         return css ? container_of(css, struct freezer, css) : NULL;
51 }
52
53 static inline struct freezer *task_freezer(struct task_struct *task)
54 {
55         return css_freezer(task_css(task, freezer_subsys_id));
56 }
57
58 static struct freezer *parent_freezer(struct freezer *freezer)
59 {
60         return css_freezer(css_parent(&freezer->css));
61 }
62
63 bool cgroup_freezing(struct task_struct *task)
64 {
65         bool ret;
66
67         rcu_read_lock();
68         ret = task_freezer(task)->state & CGROUP_FREEZING;
69         rcu_read_unlock();
70
71         return ret;
72 }
73
74 /*
75  * cgroups_write_string() limits the size of freezer state strings to
76  * CGROUP_LOCAL_BUFFER_SIZE
77  */
78 static const char *freezer_state_strs(unsigned int state)
79 {
80         if (state & CGROUP_FROZEN)
81                 return "FROZEN";
82         if (state & CGROUP_FREEZING)
83                 return "FREEZING";
84         return "THAWED";
85 };
86
87 struct cgroup_subsys freezer_subsys;
88
89 static struct cgroup_subsys_state *
90 freezer_css_alloc(struct cgroup_subsys_state *parent_css)
91 {
92         struct freezer *freezer;
93
94         freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL);
95         if (!freezer)
96                 return ERR_PTR(-ENOMEM);
97
98         spin_lock_init(&freezer->lock);
99         return &freezer->css;
100 }
101
102 /**
103  * freezer_css_online - commit creation of a freezer css
104  * @css: css being created
105  *
106  * We're committing to creation of @css.  Mark it online and inherit
107  * parent's freezing state while holding both parent's and our
108  * freezer->lock.
109  */
110 static int freezer_css_online(struct cgroup_subsys_state *css)
111 {
112         struct freezer *freezer = css_freezer(css);
113         struct freezer *parent = parent_freezer(freezer);
114
115         /*
116          * The following double locking and freezing state inheritance
117          * guarantee that @cgroup can never escape ancestors' freezing
118          * states.  See css_for_each_descendant_pre() for details.
119          */
120         if (parent)
121                 spin_lock_irq(&parent->lock);
122         spin_lock_nested(&freezer->lock, SINGLE_DEPTH_NESTING);
123
124         freezer->state |= CGROUP_FREEZER_ONLINE;
125
126         if (parent && (parent->state & CGROUP_FREEZING)) {
127                 freezer->state |= CGROUP_FREEZING_PARENT | CGROUP_FROZEN;
128                 atomic_inc(&system_freezing_cnt);
129         }
130
131         spin_unlock(&freezer->lock);
132         if (parent)
133                 spin_unlock_irq(&parent->lock);
134
135         return 0;
136 }
137
138 /**
139  * freezer_css_offline - initiate destruction of a freezer css
140  * @css: css being destroyed
141  *
142  * @css is going away.  Mark it dead and decrement system_freezing_count if
143  * it was holding one.
144  */
145 static void freezer_css_offline(struct cgroup_subsys_state *css)
146 {
147         struct freezer *freezer = css_freezer(css);
148
149         spin_lock_irq(&freezer->lock);
150
151         if (freezer->state & CGROUP_FREEZING)
152                 atomic_dec(&system_freezing_cnt);
153
154         freezer->state = 0;
155
156         spin_unlock_irq(&freezer->lock);
157 }
158
159 static void freezer_css_free(struct cgroup_subsys_state *css)
160 {
161         kfree(css_freezer(css));
162 }
163
164 /*
165  * Tasks can be migrated into a different freezer anytime regardless of its
166  * current state.  freezer_attach() is responsible for making new tasks
167  * conform to the current state.
168  *
169  * Freezer state changes and task migration are synchronized via
170  * @freezer->lock.  freezer_attach() makes the new tasks conform to the
171  * current state and all following state changes can see the new tasks.
172  */
173 static void freezer_attach(struct cgroup_subsys_state *new_css,
174                            struct cgroup_taskset *tset)
175 {
176         struct freezer *freezer = css_freezer(new_css);
177         struct task_struct *task;
178         bool clear_frozen = false;
179
180         spin_lock_irq(&freezer->lock);
181
182         /*
183          * Make the new tasks conform to the current state of @new_css.
184          * For simplicity, when migrating any task to a FROZEN cgroup, we
185          * revert it to FREEZING and let update_if_frozen() determine the
186          * correct state later.
187          *
188          * Tasks in @tset are on @new_css but may not conform to its
189          * current state before executing the following - !frozen tasks may
190          * be visible in a FROZEN cgroup and frozen tasks in a THAWED one.
191          */
192         cgroup_taskset_for_each(task, new_css, tset) {
193                 if (!(freezer->state & CGROUP_FREEZING)) {
194                         __thaw_task(task);
195                 } else {
196                         freeze_task(task);
197                         freezer->state &= ~CGROUP_FROZEN;
198                         clear_frozen = true;
199                 }
200         }
201
202         spin_unlock_irq(&freezer->lock);
203
204         /*
205          * Propagate FROZEN clearing upwards.  We may race with
206          * update_if_frozen(), but as long as both work bottom-up, either
207          * update_if_frozen() sees child's FROZEN cleared or we clear the
208          * parent's FROZEN later.  No parent w/ !FROZEN children can be
209          * left FROZEN.
210          */
211         while (clear_frozen && (freezer = parent_freezer(freezer))) {
212                 spin_lock_irq(&freezer->lock);
213                 freezer->state &= ~CGROUP_FROZEN;
214                 clear_frozen = freezer->state & CGROUP_FREEZING;
215                 spin_unlock_irq(&freezer->lock);
216         }
217 }
218
219 static void freezer_fork(struct task_struct *task)
220 {
221         struct freezer *freezer;
222
223         rcu_read_lock();
224         freezer = task_freezer(task);
225
226         /*
227          * The root cgroup is non-freezable, so we can skip the
228          * following check.
229          */
230         if (!parent_freezer(freezer))
231                 goto out;
232
233         spin_lock_irq(&freezer->lock);
234         if (freezer->state & CGROUP_FREEZING)
235                 freeze_task(task);
236         spin_unlock_irq(&freezer->lock);
237 out:
238         rcu_read_unlock();
239 }
240
241 /**
242  * update_if_frozen - update whether a cgroup finished freezing
243  * @css: css of interest
244  *
245  * Once FREEZING is initiated, transition to FROZEN is lazily updated by
246  * calling this function.  If the current state is FREEZING but not FROZEN,
247  * this function checks whether all tasks of this cgroup and the descendant
248  * cgroups finished freezing and, if so, sets FROZEN.
249  *
250  * The caller is responsible for grabbing RCU read lock and calling
251  * update_if_frozen() on all descendants prior to invoking this function.
252  *
253  * Task states and freezer state might disagree while tasks are being
254  * migrated into or out of @css, so we can't verify task states against
255  * @freezer state here.  See freezer_attach() for details.
256  */
257 static void update_if_frozen(struct cgroup_subsys_state *css)
258 {
259         struct freezer *freezer = css_freezer(css);
260         struct cgroup_subsys_state *pos;
261         struct css_task_iter it;
262         struct task_struct *task;
263
264         WARN_ON_ONCE(!rcu_read_lock_held());
265
266         spin_lock_irq(&freezer->lock);
267
268         if (!(freezer->state & CGROUP_FREEZING) ||
269             (freezer->state & CGROUP_FROZEN))
270                 goto out_unlock;
271
272         /* are all (live) children frozen? */
273         css_for_each_child(pos, css) {
274                 struct freezer *child = css_freezer(pos);
275
276                 if ((child->state & CGROUP_FREEZER_ONLINE) &&
277                     !(child->state & CGROUP_FROZEN))
278                         goto out_unlock;
279         }
280
281         /* are all tasks frozen? */
282         css_task_iter_start(css, &it);
283
284         while ((task = css_task_iter_next(&it))) {
285                 if (freezing(task)) {
286                         /*
287                          * freezer_should_skip() indicates that the task
288                          * should be skipped when determining freezing
289                          * completion.  Consider it frozen in addition to
290                          * the usual frozen condition.
291                          */
292                         if (!frozen(task) && !freezer_should_skip(task))
293                                 goto out_iter_end;
294                 }
295         }
296
297         freezer->state |= CGROUP_FROZEN;
298 out_iter_end:
299         css_task_iter_end(&it);
300 out_unlock:
301         spin_unlock_irq(&freezer->lock);
302 }
303
304 static int freezer_read(struct seq_file *m, void *v)
305 {
306         struct cgroup_subsys_state *css = seq_css(m), *pos;
307
308         rcu_read_lock();
309
310         /* update states bottom-up */
311         css_for_each_descendant_post(pos, css)
312                 update_if_frozen(pos);
313
314         rcu_read_unlock();
315
316         seq_puts(m, freezer_state_strs(css_freezer(css)->state));
317         seq_putc(m, '\n');
318         return 0;
319 }
320
321 static void freeze_cgroup(struct freezer *freezer)
322 {
323         struct css_task_iter it;
324         struct task_struct *task;
325
326         css_task_iter_start(&freezer->css, &it);
327         while ((task = css_task_iter_next(&it)))
328                 freeze_task(task);
329         css_task_iter_end(&it);
330 }
331
332 static void unfreeze_cgroup(struct freezer *freezer)
333 {
334         struct css_task_iter it;
335         struct task_struct *task;
336
337         css_task_iter_start(&freezer->css, &it);
338         while ((task = css_task_iter_next(&it)))
339                 __thaw_task(task);
340         css_task_iter_end(&it);
341 }
342
343 /**
344  * freezer_apply_state - apply state change to a single cgroup_freezer
345  * @freezer: freezer to apply state change to
346  * @freeze: whether to freeze or unfreeze
347  * @state: CGROUP_FREEZING_* flag to set or clear
348  *
349  * Set or clear @state on @cgroup according to @freeze, and perform
350  * freezing or thawing as necessary.
351  */
352 static void freezer_apply_state(struct freezer *freezer, bool freeze,
353                                 unsigned int state)
354 {
355         /* also synchronizes against task migration, see freezer_attach() */
356         lockdep_assert_held(&freezer->lock);
357
358         if (!(freezer->state & CGROUP_FREEZER_ONLINE))
359                 return;
360
361         if (freeze) {
362                 if (!(freezer->state & CGROUP_FREEZING))
363                         atomic_inc(&system_freezing_cnt);
364                 freezer->state |= state;
365                 freeze_cgroup(freezer);
366         } else {
367                 bool was_freezing = freezer->state & CGROUP_FREEZING;
368
369                 freezer->state &= ~state;
370
371                 if (!(freezer->state & CGROUP_FREEZING)) {
372                         if (was_freezing)
373                                 atomic_dec(&system_freezing_cnt);
374                         freezer->state &= ~CGROUP_FROZEN;
375                         unfreeze_cgroup(freezer);
376                 }
377         }
378 }
379
380 /**
381  * freezer_change_state - change the freezing state of a cgroup_freezer
382  * @freezer: freezer of interest
383  * @freeze: whether to freeze or thaw
384  *
385  * Freeze or thaw @freezer according to @freeze.  The operations are
386  * recursive - all descendants of @freezer will be affected.
387  */
388 static void freezer_change_state(struct freezer *freezer, bool freeze)
389 {
390         struct cgroup_subsys_state *pos;
391
392         /*
393          * Update all its descendants in pre-order traversal.  Each
394          * descendant will try to inherit its parent's FREEZING state as
395          * CGROUP_FREEZING_PARENT.
396          */
397         rcu_read_lock();
398         css_for_each_descendant_pre(pos, &freezer->css) {
399                 struct freezer *pos_f = css_freezer(pos);
400                 struct freezer *parent = parent_freezer(pos_f);
401
402                 spin_lock_irq(&pos_f->lock);
403
404                 if (pos_f == freezer) {
405                         freezer_apply_state(pos_f, freeze,
406                                             CGROUP_FREEZING_SELF);
407                 } else {
408                         /*
409                          * Our update to @parent->state is already visible
410                          * which is all we need.  No need to lock @parent.
411                          * For more info on synchronization, see
412                          * freezer_post_create().
413                          */
414                         freezer_apply_state(pos_f,
415                                             parent->state & CGROUP_FREEZING,
416                                             CGROUP_FREEZING_PARENT);
417                 }
418
419                 spin_unlock_irq(&pos_f->lock);
420         }
421         rcu_read_unlock();
422 }
423
424 static int freezer_write(struct cgroup_subsys_state *css, struct cftype *cft,
425                          const char *buffer)
426 {
427         bool freeze;
428
429         if (strcmp(buffer, freezer_state_strs(0)) == 0)
430                 freeze = false;
431         else if (strcmp(buffer, freezer_state_strs(CGROUP_FROZEN)) == 0)
432                 freeze = true;
433         else
434                 return -EINVAL;
435
436         freezer_change_state(css_freezer(css), freeze);
437         return 0;
438 }
439
440 static u64 freezer_self_freezing_read(struct cgroup_subsys_state *css,
441                                       struct cftype *cft)
442 {
443         struct freezer *freezer = css_freezer(css);
444
445         return (bool)(freezer->state & CGROUP_FREEZING_SELF);
446 }
447
448 static u64 freezer_parent_freezing_read(struct cgroup_subsys_state *css,
449                                         struct cftype *cft)
450 {
451         struct freezer *freezer = css_freezer(css);
452
453         return (bool)(freezer->state & CGROUP_FREEZING_PARENT);
454 }
455
456 static struct cftype files[] = {
457         {
458                 .name = "state",
459                 .flags = CFTYPE_NOT_ON_ROOT,
460                 .seq_show = freezer_read,
461                 .write_string = freezer_write,
462         },
463         {
464                 .name = "self_freezing",
465                 .flags = CFTYPE_NOT_ON_ROOT,
466                 .read_u64 = freezer_self_freezing_read,
467         },
468         {
469                 .name = "parent_freezing",
470                 .flags = CFTYPE_NOT_ON_ROOT,
471                 .read_u64 = freezer_parent_freezing_read,
472         },
473         { }     /* terminate */
474 };
475
476 struct cgroup_subsys freezer_subsys = {
477         .name           = "freezer",
478         .css_alloc      = freezer_css_alloc,
479         .css_online     = freezer_css_online,
480         .css_offline    = freezer_css_offline,
481         .css_free       = freezer_css_free,
482         .subsys_id      = freezer_subsys_id,
483         .attach         = freezer_attach,
484         .fork           = freezer_fork,
485         .base_cftypes   = files,
486 };