idr: make idr_get_next() good for rcu_read_lock()
[GitHub/mt8127/android_kernel_alcatel_ttab.git] / include / linux / cgroup.h
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1#ifndef _LINUX_CGROUP_H
2#define _LINUX_CGROUP_H
3/*
4 * cgroup interface
5 *
6 * Copyright (C) 2003 BULL SA
7 * Copyright (C) 2004-2006 Silicon Graphics, Inc.
8 *
9 */
10
11#include <linux/sched.h>
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12#include <linux/cpumask.h>
13#include <linux/nodemask.h>
14#include <linux/rcupdate.h>
846c7bb0 15#include <linux/cgroupstats.h>
31a7df01 16#include <linux/prio_heap.h>
cc31edce 17#include <linux/rwsem.h>
38460b48 18#include <linux/idr.h>
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19
20#ifdef CONFIG_CGROUPS
21
22struct cgroupfs_root;
23struct cgroup_subsys;
24struct inode;
84eea842 25struct cgroup;
38460b48 26struct css_id;
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27
28extern int cgroup_init_early(void);
29extern int cgroup_init(void);
ddbcc7e8 30extern void cgroup_lock(void);
d11c563d 31extern int cgroup_lock_is_held(void);
84eea842 32extern bool cgroup_lock_live_group(struct cgroup *cgrp);
ddbcc7e8 33extern void cgroup_unlock(void);
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34extern void cgroup_fork(struct task_struct *p);
35extern void cgroup_fork_callbacks(struct task_struct *p);
817929ec 36extern void cgroup_post_fork(struct task_struct *p);
b4f48b63 37extern void cgroup_exit(struct task_struct *p, int run_callbacks);
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38extern int cgroupstats_build(struct cgroupstats *stats,
39 struct dentry *dentry);
e6a1105b 40extern int cgroup_load_subsys(struct cgroup_subsys *ss);
cf5d5941 41extern void cgroup_unload_subsys(struct cgroup_subsys *ss);
ddbcc7e8 42
828c0950 43extern const struct file_operations proc_cgroup_operations;
a424316c 44
aae8aab4 45/* Define the enumeration of all builtin cgroup subsystems */
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46#define SUBSYS(_x) _x ## _subsys_id,
47enum cgroup_subsys_id {
48#include <linux/cgroup_subsys.h>
aae8aab4 49 CGROUP_BUILTIN_SUBSYS_COUNT
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50};
51#undef SUBSYS
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52/*
53 * This define indicates the maximum number of subsystems that can be loaded
54 * at once. We limit to this many since cgroupfs_root has subsys_bits to keep
55 * track of all of them.
56 */
57#define CGROUP_SUBSYS_COUNT (BITS_PER_BYTE*sizeof(unsigned long))
817929ec 58
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59/* Per-subsystem/per-cgroup state maintained by the system. */
60struct cgroup_subsys_state {
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61 /*
62 * The cgroup that this subsystem is attached to. Useful
ddbcc7e8 63 * for subsystems that want to know about the cgroup
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64 * hierarchy structure
65 */
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66 struct cgroup *cgroup;
67
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68 /*
69 * State maintained by the cgroup system to allow subsystems
e7c5ec91 70 * to be "busy". Should be accessed via css_get(),
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71 * css_tryget() and and css_put().
72 */
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73
74 atomic_t refcnt;
75
76 unsigned long flags;
38460b48 77 /* ID for this css, if possible */
2c392b8c 78 struct css_id __rcu *id;
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79};
80
81/* bits in struct cgroup_subsys_state flags field */
82enum {
83 CSS_ROOT, /* This CSS is the root of the subsystem */
e7c5ec91 84 CSS_REMOVED, /* This CSS is dead */
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85};
86
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87/* Caller must verify that the css is not for root cgroup */
88static inline void __css_get(struct cgroup_subsys_state *css, int count)
89{
90 atomic_add(count, &css->refcnt);
91}
92
ddbcc7e8 93/*
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94 * Call css_get() to hold a reference on the css; it can be used
95 * for a reference obtained via:
96 * - an existing ref-counted reference to the css
97 * - task->cgroups for a locked task
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98 */
99
100static inline void css_get(struct cgroup_subsys_state *css)
101{
102 /* We don't need to reference count the root state */
103 if (!test_bit(CSS_ROOT, &css->flags))
d7b9fff7 104 __css_get(css, 1);
ddbcc7e8 105}
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106
107static inline bool css_is_removed(struct cgroup_subsys_state *css)
108{
109 return test_bit(CSS_REMOVED, &css->flags);
110}
111
112/*
113 * Call css_tryget() to take a reference on a css if your existing
114 * (known-valid) reference isn't already ref-counted. Returns false if
115 * the css has been destroyed.
116 */
117
118static inline bool css_tryget(struct cgroup_subsys_state *css)
119{
120 if (test_bit(CSS_ROOT, &css->flags))
121 return true;
122 while (!atomic_inc_not_zero(&css->refcnt)) {
123 if (test_bit(CSS_REMOVED, &css->flags))
124 return false;
804b3c28 125 cpu_relax();
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126 }
127 return true;
128}
129
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130/*
131 * css_put() should be called to release a reference taken by
e7c5ec91 132 * css_get() or css_tryget()
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133 */
134
d7b9fff7 135extern void __css_put(struct cgroup_subsys_state *css, int count);
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136static inline void css_put(struct cgroup_subsys_state *css)
137{
138 if (!test_bit(CSS_ROOT, &css->flags))
d7b9fff7 139 __css_put(css, 1);
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140}
141
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142/* bits in struct cgroup flags field */
143enum {
144 /* Control Group is dead */
145 CGRP_REMOVED,
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146 /*
147 * Control Group has previously had a child cgroup or a task,
148 * but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
149 */
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150 CGRP_RELEASABLE,
151 /* Control Group requires release notifications to userspace */
152 CGRP_NOTIFY_ON_RELEASE,
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153 /*
154 * A thread in rmdir() is wating for this cgroup.
155 */
156 CGRP_WAIT_ON_RMDIR,
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157 /*
158 * Clone cgroup values when creating a new child cgroup
159 */
160 CGRP_CLONE_CHILDREN,
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161};
162
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163struct cgroup {
164 unsigned long flags; /* "unsigned long" so bitops work */
165
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166 /*
167 * count users of this cgroup. >0 means busy, but doesn't
168 * necessarily indicate the number of tasks in the cgroup
169 */
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170 atomic_t count;
171
172 /*
173 * We link our 'sibling' struct into our parent's 'children'.
174 * Our children link their 'sibling' into our 'children'.
175 */
176 struct list_head sibling; /* my parent's children */
177 struct list_head children; /* my children */
178
d20a390a 179 struct cgroup *parent; /* my parent */
2c392b8c 180 struct dentry __rcu *dentry; /* cgroup fs entry, RCU protected */
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181
182 /* Private pointers for each registered subsystem */
183 struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
184
185 struct cgroupfs_root *root;
186 struct cgroup *top_cgroup;
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187
188 /*
189 * List of cg_cgroup_links pointing at css_sets with
190 * tasks in this cgroup. Protected by css_set_lock
191 */
192 struct list_head css_sets;
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193
194 /*
195 * Linked list running through all cgroups that can
196 * potentially be reaped by the release agent. Protected by
197 * release_list_lock
198 */
199 struct list_head release_list;
cc31edce 200
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201 /*
202 * list of pidlists, up to two for each namespace (one for procs, one
203 * for tasks); created on demand.
204 */
205 struct list_head pidlists;
206 struct mutex pidlist_mutex;
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207
208 /* For RCU-protected deletion */
209 struct rcu_head rcu_head;
0dea1168 210
25985edc 211 /* List of events which userspace want to receive */
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212 struct list_head event_list;
213 spinlock_t event_list_lock;
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214};
215
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216/*
217 * A css_set is a structure holding pointers to a set of
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218 * cgroup_subsys_state objects. This saves space in the task struct
219 * object and speeds up fork()/exit(), since a single inc/dec and a
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220 * list_add()/del() can bump the reference count on the entire cgroup
221 * set for a task.
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222 */
223
224struct css_set {
225
226 /* Reference count */
146aa1bd 227 atomic_t refcount;
817929ec 228
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229 /*
230 * List running through all cgroup groups in the same hash
231 * slot. Protected by css_set_lock
232 */
233 struct hlist_node hlist;
234
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235 /*
236 * List running through all tasks using this cgroup
237 * group. Protected by css_set_lock
238 */
239 struct list_head tasks;
240
241 /*
242 * List of cg_cgroup_link objects on link chains from
243 * cgroups referenced from this css_set. Protected by
244 * css_set_lock
245 */
246 struct list_head cg_links;
247
248 /*
249 * Set of subsystem states, one for each subsystem. This array
250 * is immutable after creation apart from the init_css_set
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251 * during subsystem registration (at boot time) and modular subsystem
252 * loading/unloading.
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253 */
254 struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
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255
256 /* For RCU-protected deletion */
257 struct rcu_head rcu_head;
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258};
259
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260/*
261 * cgroup_map_cb is an abstract callback API for reporting map-valued
262 * control files
263 */
264
265struct cgroup_map_cb {
266 int (*fill)(struct cgroup_map_cb *cb, const char *key, u64 value);
267 void *state;
268};
269
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270/*
271 * struct cftype: handler definitions for cgroup control files
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272 *
273 * When reading/writing to a file:
a043e3b2 274 * - the cgroup to use is file->f_dentry->d_parent->d_fsdata
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275 * - the 'cftype' of the file is file->f_dentry->d_fsdata
276 */
277
278#define MAX_CFTYPE_NAME 64
279struct cftype {
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280 /*
281 * By convention, the name should begin with the name of the
282 * subsystem, followed by a period
283 */
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284 char name[MAX_CFTYPE_NAME];
285 int private;
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286 /*
287 * If not 0, file mode is set to this value, otherwise it will
288 * be figured out automatically
289 */
a5e7ed32 290 umode_t mode;
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291
292 /*
293 * If non-zero, defines the maximum length of string that can
294 * be passed to write_string; defaults to 64
295 */
296 size_t max_write_len;
297
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298 int (*open)(struct inode *inode, struct file *file);
299 ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
300 struct file *file,
301 char __user *buf, size_t nbytes, loff_t *ppos);
ddbcc7e8 302 /*
f4c753b7 303 * read_u64() is a shortcut for the common case of returning a
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304 * single integer. Use it in place of read()
305 */
ce16b49d 306 u64 (*read_u64)(struct cgroup *cgrp, struct cftype *cft);
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307 /*
308 * read_s64() is a signed version of read_u64()
309 */
ce16b49d 310 s64 (*read_s64)(struct cgroup *cgrp, struct cftype *cft);
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311 /*
312 * read_map() is used for defining a map of key/value
313 * pairs. It should call cb->fill(cb, key, value) for each
314 * entry. The key/value pairs (and their ordering) should not
315 * change between reboots.
316 */
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317 int (*read_map)(struct cgroup *cont, struct cftype *cft,
318 struct cgroup_map_cb *cb);
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319 /*
320 * read_seq_string() is used for outputting a simple sequence
321 * using seqfile.
322 */
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323 int (*read_seq_string)(struct cgroup *cont, struct cftype *cft,
324 struct seq_file *m);
91796569 325
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326 ssize_t (*write)(struct cgroup *cgrp, struct cftype *cft,
327 struct file *file,
328 const char __user *buf, size_t nbytes, loff_t *ppos);
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329
330 /*
f4c753b7 331 * write_u64() is a shortcut for the common case of accepting
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332 * a single integer (as parsed by simple_strtoull) from
333 * userspace. Use in place of write(); return 0 or error.
334 */
ce16b49d 335 int (*write_u64)(struct cgroup *cgrp, struct cftype *cft, u64 val);
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336 /*
337 * write_s64() is a signed version of write_u64()
338 */
ce16b49d 339 int (*write_s64)(struct cgroup *cgrp, struct cftype *cft, s64 val);
355e0c48 340
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341 /*
342 * write_string() is passed a nul-terminated kernelspace
343 * buffer of maximum length determined by max_write_len.
344 * Returns 0 or -ve error code.
345 */
346 int (*write_string)(struct cgroup *cgrp, struct cftype *cft,
347 const char *buffer);
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348 /*
349 * trigger() callback can be used to get some kick from the
350 * userspace, when the actual string written is not important
351 * at all. The private field can be used to determine the
352 * kick type for multiplexing.
353 */
354 int (*trigger)(struct cgroup *cgrp, unsigned int event);
355
ce16b49d 356 int (*release)(struct inode *inode, struct file *file);
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357
358 /*
359 * register_event() callback will be used to add new userspace
360 * waiter for changes related to the cftype. Implement it if
361 * you want to provide this functionality. Use eventfd_signal()
362 * on eventfd to send notification to userspace.
363 */
364 int (*register_event)(struct cgroup *cgrp, struct cftype *cft,
365 struct eventfd_ctx *eventfd, const char *args);
366 /*
367 * unregister_event() callback will be called when userspace
368 * closes the eventfd or on cgroup removing.
369 * This callback must be implemented, if you want provide
370 * notification functionality.
0dea1168 371 */
907860ed 372 void (*unregister_event)(struct cgroup *cgrp, struct cftype *cft,
0dea1168 373 struct eventfd_ctx *eventfd);
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374};
375
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376struct cgroup_scanner {
377 struct cgroup *cg;
378 int (*test_task)(struct task_struct *p, struct cgroup_scanner *scan);
379 void (*process_task)(struct task_struct *p,
380 struct cgroup_scanner *scan);
381 struct ptr_heap *heap;
bd1a8ab7 382 void *data;
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383};
384
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385/*
386 * Add a new file to the given cgroup directory. Should only be
387 * called by subsystems from within a populate() method
388 */
ffd2d883 389int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
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390 const struct cftype *cft);
391
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392/*
393 * Add a set of new files to the given cgroup directory. Should
394 * only be called by subsystems from within a populate() method
395 */
ffd2d883 396int cgroup_add_files(struct cgroup *cgrp,
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397 struct cgroup_subsys *subsys,
398 const struct cftype cft[],
399 int count);
400
ffd2d883 401int cgroup_is_removed(const struct cgroup *cgrp);
ddbcc7e8 402
ffd2d883 403int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
ddbcc7e8 404
ffd2d883 405int cgroup_task_count(const struct cgroup *cgrp);
bbcb81d0 406
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407/* Return true if cgrp is a descendant of the task's cgroup */
408int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task);
ddbcc7e8 409
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410/*
411 * When the subsys has to access css and may add permanent refcnt to css,
412 * it should take care of racy conditions with rmdir(). Following set of
413 * functions, is for stop/restart rmdir if necessary.
414 * Because these will call css_get/put, "css" should be alive css.
415 *
416 * cgroup_exclude_rmdir();
417 * ...do some jobs which may access arbitrary empty cgroup
418 * cgroup_release_and_wakeup_rmdir();
419 *
420 * When someone removes a cgroup while cgroup_exclude_rmdir() holds it,
421 * it sleeps and cgroup_release_and_wakeup_rmdir() will wake him up.
422 */
423
424void cgroup_exclude_rmdir(struct cgroup_subsys_state *css);
425void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css);
426
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427/*
428 * Control Group taskset, used to pass around set of tasks to cgroup_subsys
429 * methods.
430 */
431struct cgroup_taskset;
432struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
433struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
434struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset);
435int cgroup_taskset_size(struct cgroup_taskset *tset);
436
437/**
438 * cgroup_taskset_for_each - iterate cgroup_taskset
439 * @task: the loop cursor
440 * @skip_cgrp: skip if task's cgroup matches this, %NULL to iterate through all
441 * @tset: taskset to iterate
442 */
443#define cgroup_taskset_for_each(task, skip_cgrp, tset) \
444 for ((task) = cgroup_taskset_first((tset)); (task); \
445 (task) = cgroup_taskset_next((tset))) \
446 if (!(skip_cgrp) || \
447 cgroup_taskset_cur_cgroup((tset)) != (skip_cgrp))
448
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449/*
450 * Control Group subsystem type.
451 * See Documentation/cgroups/cgroups.txt for details
452 */
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453
454struct cgroup_subsys {
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455 struct cgroup_subsys_state *(*create)(struct cgroup *cgrp);
456 int (*pre_destroy)(struct cgroup *cgrp);
457 void (*destroy)(struct cgroup *cgrp);
458 int (*can_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
459 void (*cancel_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
460 void (*attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
461 void (*fork)(struct task_struct *task);
462 void (*exit)(struct cgroup *cgrp, struct cgroup *old_cgrp,
463 struct task_struct *task);
464 int (*populate)(struct cgroup_subsys *ss, struct cgroup *cgrp);
465 void (*post_clone)(struct cgroup *cgrp);
466 void (*bind)(struct cgroup *root);
e5991371 467
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468 int subsys_id;
469 int active;
8bab8dde 470 int disabled;
ddbcc7e8 471 int early_init;
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472 /*
473 * True if this subsys uses ID. ID is not available before cgroup_init()
474 * (not available in early_init time.)
475 */
476 bool use_id;
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477#define MAX_CGROUP_TYPE_NAMELEN 32
478 const char *name;
479
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480 /*
481 * Protects sibling/children links of cgroups in this
482 * hierarchy, plus protects which hierarchy (or none) the
483 * subsystem is a part of (i.e. root/sibling). To avoid
484 * potential deadlocks, the following operations should not be
485 * undertaken while holding any hierarchy_mutex:
486 *
487 * - allocating memory
488 * - initiating hotplug events
489 */
490 struct mutex hierarchy_mutex;
cfebe563 491 struct lock_class_key subsys_key;
ddbcc7e8 492
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493 /*
494 * Link to parent, and list entry in parent's children.
495 * Protected by this->hierarchy_mutex and cgroup_lock()
496 */
497 struct cgroupfs_root *root;
ddbcc7e8 498 struct list_head sibling;
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499 /* used when use_id == true */
500 struct idr idr;
c1e2ee2d 501 rwlock_t id_lock;
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502
503 /* should be defined only by modular subsystems */
504 struct module *module;
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505};
506
507#define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
508#include <linux/cgroup_subsys.h>
509#undef SUBSYS
510
511static inline struct cgroup_subsys_state *cgroup_subsys_state(
ffd2d883 512 struct cgroup *cgrp, int subsys_id)
ddbcc7e8 513{
ffd2d883 514 return cgrp->subsys[subsys_id];
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515}
516
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517/*
518 * function to get the cgroup_subsys_state which allows for extra
519 * rcu_dereference_check() conditions, such as locks used during the
520 * cgroup_subsys::attach() methods.
521 */
522#define task_subsys_state_check(task, subsys_id, __c) \
523 rcu_dereference_check(task->cgroups->subsys[subsys_id], \
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524 lockdep_is_held(&task->alloc_lock) || \
525 cgroup_lock_is_held() || (__c))
526
527static inline struct cgroup_subsys_state *
528task_subsys_state(struct task_struct *task, int subsys_id)
ddbcc7e8 529{
dc61b1d6 530 return task_subsys_state_check(task, subsys_id, false);
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531}
532
533static inline struct cgroup* task_cgroup(struct task_struct *task,
534 int subsys_id)
535{
536 return task_subsys_state(task, subsys_id)->cgroup;
537}
538
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539/* A cgroup_iter should be treated as an opaque object */
540struct cgroup_iter {
541 struct list_head *cg_link;
542 struct list_head *task;
543};
544
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545/*
546 * To iterate across the tasks in a cgroup:
817929ec 547 *
b595076a 548 * 1) call cgroup_iter_start to initialize an iterator
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549 *
550 * 2) call cgroup_iter_next() to retrieve member tasks until it
551 * returns NULL or until you want to end the iteration
552 *
553 * 3) call cgroup_iter_end() to destroy the iterator.
31a7df01 554 *
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555 * Or, call cgroup_scan_tasks() to iterate through every task in a
556 * cgroup - cgroup_scan_tasks() holds the css_set_lock when calling
557 * the test_task() callback, but not while calling the process_task()
558 * callback.
817929ec 559 */
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560void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it);
561struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
817929ec 562 struct cgroup_iter *it);
ffd2d883 563void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it);
31a7df01 564int cgroup_scan_tasks(struct cgroup_scanner *scan);
956db3ca 565int cgroup_attach_task(struct cgroup *, struct task_struct *);
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566int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
567
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568/*
569 * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
570 * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
571 * CSS ID is assigned at cgroup allocation (create) automatically
572 * and removed when subsys calls free_css_id() function. This is because
573 * the lifetime of cgroup_subsys_state is subsys's matter.
574 *
575 * Looking up and scanning function should be called under rcu_read_lock().
576 * Taking cgroup_mutex()/hierarchy_mutex() is not necessary for following calls.
577 * But the css returned by this routine can be "not populated yet" or "being
578 * destroyed". The caller should check css and cgroup's status.
579 */
580
581/*
582 * Typically Called at ->destroy(), or somewhere the subsys frees
583 * cgroup_subsys_state.
584 */
585void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
586
587/* Find a cgroup_subsys_state which has given ID */
588
589struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id);
590
591/*
592 * Get a cgroup whose id is greater than or equal to id under tree of root.
593 * Returning a cgroup_subsys_state or NULL.
594 */
595struct cgroup_subsys_state *css_get_next(struct cgroup_subsys *ss, int id,
596 struct cgroup_subsys_state *root, int *foundid);
597
598/* Returns true if root is ancestor of cg */
599bool css_is_ancestor(struct cgroup_subsys_state *cg,
0b7f569e 600 const struct cgroup_subsys_state *root);
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601
602/* Get id and depth of css */
603unsigned short css_id(struct cgroup_subsys_state *css);
604unsigned short css_depth(struct cgroup_subsys_state *css);
e5d1367f 605struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id);
38460b48 606
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607#else /* !CONFIG_CGROUPS */
608
609static inline int cgroup_init_early(void) { return 0; }
610static inline int cgroup_init(void) { return 0; }
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611static inline void cgroup_fork(struct task_struct *p) {}
612static inline void cgroup_fork_callbacks(struct task_struct *p) {}
817929ec 613static inline void cgroup_post_fork(struct task_struct *p) {}
b4f48b63 614static inline void cgroup_exit(struct task_struct *p, int callbacks) {}
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615
616static inline void cgroup_lock(void) {}
617static inline void cgroup_unlock(void) {}
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618static inline int cgroupstats_build(struct cgroupstats *stats,
619 struct dentry *dentry)
620{
621 return -EINVAL;
622}
ddbcc7e8 623
d7926ee3 624/* No cgroups - nothing to do */
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625static inline int cgroup_attach_task_all(struct task_struct *from,
626 struct task_struct *t)
627{
628 return 0;
629}
d7926ee3 630
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631#endif /* !CONFIG_CGROUPS */
632
633#endif /* _LINUX_CGROUP_H */