1 #ifndef _LINUX_CGROUP_H
2 #define _LINUX_CGROUP_H
6 * Copyright (C) 2003 BULL SA
7 * Copyright (C) 2004-2006 Silicon Graphics, Inc.
11 #include <linux/sched.h>
12 #include <linux/cpumask.h>
13 #include <linux/nodemask.h>
14 #include <linux/rcupdate.h>
15 #include <linux/rculist.h>
16 #include <linux/cgroupstats.h>
17 #include <linux/prio_heap.h>
18 #include <linux/rwsem.h>
19 #include <linux/idr.h>
20 #include <linux/workqueue.h>
21 #include <linux/xattr.h>
23 #include <linux/percpu-refcount.h>
34 extern int cgroup_init_early(void);
35 extern int cgroup_init(void);
36 extern void cgroup_fork(struct task_struct *p);
37 extern void cgroup_post_fork(struct task_struct *p);
38 extern void cgroup_exit(struct task_struct *p, int run_callbacks);
39 extern int cgroupstats_build(struct cgroupstats *stats,
40 struct dentry *dentry);
41 extern int cgroup_load_subsys(struct cgroup_subsys *ss);
42 extern void cgroup_unload_subsys(struct cgroup_subsys *ss);
44 extern int proc_cgroup_show(struct seq_file *, void *);
47 * Define the enumeration of all cgroup subsystems.
49 * We define ids for builtin subsystems and then modular ones.
51 #define SUBSYS(_x) _x ## _subsys_id,
52 enum cgroup_subsys_id {
53 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
54 #include <linux/cgroup_subsys.h>
55 #undef IS_SUBSYS_ENABLED
56 CGROUP_BUILTIN_SUBSYS_COUNT,
58 __CGROUP_SUBSYS_TEMP_PLACEHOLDER = CGROUP_BUILTIN_SUBSYS_COUNT - 1,
60 #define IS_SUBSYS_ENABLED(option) IS_MODULE(option)
61 #include <linux/cgroup_subsys.h>
62 #undef IS_SUBSYS_ENABLED
67 /* Per-subsystem/per-cgroup state maintained by the system. */
68 struct cgroup_subsys_state {
70 * The cgroup that this subsystem is attached to. Useful
71 * for subsystems that want to know about the cgroup
74 struct cgroup *cgroup;
76 /* reference count - access via css_[try]get() and css_put() */
77 struct percpu_ref refcnt;
80 /* ID for this css, if possible */
81 struct css_id __rcu *id;
83 /* Used to put @cgroup->dentry on the last css_put() */
84 struct work_struct dput_work;
87 /* bits in struct cgroup_subsys_state flags field */
89 CSS_ROOT = (1 << 0), /* this CSS is the root of the subsystem */
90 CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */
94 * css_get - obtain a reference on the specified css
97 * The caller must already have a reference.
99 static inline void css_get(struct cgroup_subsys_state *css)
101 /* We don't need to reference count the root state */
102 if (!(css->flags & CSS_ROOT))
103 percpu_ref_get(&css->refcnt);
107 * css_tryget - try to obtain a reference on the specified css
110 * Obtain a reference on @css if it's alive. The caller naturally needs to
111 * ensure that @css is accessible but doesn't have to be holding a
112 * reference on it - IOW, RCU protected access is good enough for this
113 * function. Returns %true if a reference count was successfully obtained;
116 static inline bool css_tryget(struct cgroup_subsys_state *css)
118 if (css->flags & CSS_ROOT)
120 return percpu_ref_tryget(&css->refcnt);
124 * css_put - put a css reference
127 * Put a reference obtained via css_get() and css_tryget().
129 static inline void css_put(struct cgroup_subsys_state *css)
131 if (!(css->flags & CSS_ROOT))
132 percpu_ref_put(&css->refcnt);
135 /* bits in struct cgroup flags field */
137 /* Control Group is dead */
140 * Control Group has previously had a child cgroup or a task,
141 * but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
144 /* Control Group requires release notifications to userspace */
145 CGRP_NOTIFY_ON_RELEASE,
147 * Clone the parent's configuration when creating a new child
148 * cpuset cgroup. For historical reasons, this option can be
149 * specified at mount time and thus is implemented here.
151 CGRP_CPUSET_CLONE_CHILDREN,
152 /* see the comment above CGRP_ROOT_SANE_BEHAVIOR for details */
157 struct rcu_head rcu_head;
162 unsigned long flags; /* "unsigned long" so bitops work */
164 int id; /* ida allocated in-hierarchy ID */
167 * We link our 'sibling' struct into our parent's 'children'.
168 * Our children link their 'sibling' into our 'children'.
170 struct list_head sibling; /* my parent's children */
171 struct list_head children; /* my children */
172 struct list_head files; /* my files */
174 struct cgroup *parent; /* my parent */
175 struct dentry *dentry; /* cgroup fs entry, RCU protected */
178 * Monotonically increasing unique serial number which defines a
179 * uniform order among all cgroups. It's guaranteed that all
180 * ->children lists are in the ascending order of ->serial_nr.
181 * It's used to allow interrupting and resuming iterations.
186 * This is a copy of dentry->d_name, and it's needed because
187 * we can't use dentry->d_name in cgroup_path().
189 * You must acquire rcu_read_lock() to access cgrp->name, and
190 * the only place that can change it is rename(), which is
191 * protected by parent dir's i_mutex.
193 * Normally you should use cgroup_name() wrapper rather than
194 * access it directly.
196 struct cgroup_name __rcu *name;
198 /* Private pointers for each registered subsystem */
199 struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
201 struct cgroupfs_root *root;
204 * List of cgrp_cset_links pointing at css_sets with tasks in this
205 * cgroup. Protected by css_set_lock.
207 struct list_head cset_links;
210 * Linked list running through all cgroups that can
211 * potentially be reaped by the release agent. Protected by
214 struct list_head release_list;
217 * list of pidlists, up to two for each namespace (one for procs, one
218 * for tasks); created on demand.
220 struct list_head pidlists;
221 struct mutex pidlist_mutex;
223 /* For css percpu_ref killing and RCU-protected deletion */
224 struct rcu_head rcu_head;
225 struct work_struct destroy_work;
226 atomic_t css_kill_cnt;
228 /* List of events which userspace want to receive */
229 struct list_head event_list;
230 spinlock_t event_list_lock;
232 /* directory xattrs */
233 struct simple_xattrs xattrs;
236 #define MAX_CGROUP_ROOT_NAMELEN 64
238 /* cgroupfs_root->flags */
241 * Unfortunately, cgroup core and various controllers are riddled
242 * with idiosyncrasies and pointless options. The following flag,
243 * when set, will force sane behavior - some options are forced on,
244 * others are disallowed, and some controllers will change their
245 * hierarchical or other behaviors.
247 * The set of behaviors affected by this flag are still being
248 * determined and developed and the mount option for this flag is
249 * prefixed with __DEVEL__. The prefix will be dropped once we
250 * reach the point where all behaviors are compatible with the
251 * planned unified hierarchy, which will automatically turn on this
254 * The followings are the behaviors currently affected this flag.
256 * - Mount options "noprefix" and "clone_children" are disallowed.
257 * Also, cgroupfs file cgroup.clone_children is not created.
259 * - When mounting an existing superblock, mount options should
262 * - Remount is disallowed.
264 * - "tasks" is removed. Everything should be at process
265 * granularity. Use "cgroup.procs" instead.
267 * - "release_agent" and "notify_on_release" are removed.
268 * Replacement notification mechanism will be implemented.
270 * - rename(2) is disallowed.
272 * - memcg: use_hierarchy is on by default and the cgroup file for
273 * the flag is not created.
275 CGRP_ROOT_SANE_BEHAVIOR = (1 << 0),
277 CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
278 CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
282 * A cgroupfs_root represents the root of a cgroup hierarchy, and may be
283 * associated with a superblock to form an active hierarchy. This is
284 * internal to cgroup core. Don't access directly from controllers.
286 struct cgroupfs_root {
287 struct super_block *sb;
289 /* The bitmask of subsystems attached to this hierarchy */
290 unsigned long subsys_mask;
292 /* Unique id for this hierarchy. */
295 /* A list running through the attached subsystems */
296 struct list_head subsys_list;
298 /* The root cgroup for this hierarchy */
299 struct cgroup top_cgroup;
301 /* Tracks how many cgroups are currently defined in hierarchy.*/
302 int number_of_cgroups;
304 /* A list running through the active hierarchies */
305 struct list_head root_list;
307 /* Hierarchy-specific flags */
310 /* IDs for cgroups in this hierarchy */
311 struct ida cgroup_ida;
313 /* The path to use for release notifications. */
314 char release_agent_path[PATH_MAX];
316 /* The name for this hierarchy - may be empty */
317 char name[MAX_CGROUP_ROOT_NAMELEN];
321 * A css_set is a structure holding pointers to a set of
322 * cgroup_subsys_state objects. This saves space in the task struct
323 * object and speeds up fork()/exit(), since a single inc/dec and a
324 * list_add()/del() can bump the reference count on the entire cgroup
330 /* Reference count */
334 * List running through all cgroup groups in the same hash
335 * slot. Protected by css_set_lock
337 struct hlist_node hlist;
340 * List running through all tasks using this cgroup
341 * group. Protected by css_set_lock
343 struct list_head tasks;
346 * List of cgrp_cset_links pointing at cgroups referenced from this
347 * css_set. Protected by css_set_lock.
349 struct list_head cgrp_links;
352 * Set of subsystem states, one for each subsystem. This array
353 * is immutable after creation apart from the init_css_set
354 * during subsystem registration (at boot time) and modular subsystem
357 struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
359 /* For RCU-protected deletion */
360 struct rcu_head rcu_head;
364 * cgroup_map_cb is an abstract callback API for reporting map-valued
368 struct cgroup_map_cb {
369 int (*fill)(struct cgroup_map_cb *cb, const char *key, u64 value);
374 * struct cftype: handler definitions for cgroup control files
376 * When reading/writing to a file:
377 * - the cgroup to use is file->f_dentry->d_parent->d_fsdata
378 * - the 'cftype' of the file is file->f_dentry->d_fsdata
383 CFTYPE_ONLY_ON_ROOT = (1 << 0), /* only create on root cg */
384 CFTYPE_NOT_ON_ROOT = (1 << 1), /* don't create on root cg */
385 CFTYPE_INSANE = (1 << 2), /* don't create if sane_behavior */
388 #define MAX_CFTYPE_NAME 64
392 * By convention, the name should begin with the name of the
393 * subsystem, followed by a period. Zero length string indicates
394 * end of cftype array.
396 char name[MAX_CFTYPE_NAME];
399 * If not 0, file mode is set to this value, otherwise it will
400 * be figured out automatically
405 * If non-zero, defines the maximum length of string that can
406 * be passed to write_string; defaults to 64
408 size_t max_write_len;
413 int (*open)(struct inode *inode, struct file *file);
414 ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
416 char __user *buf, size_t nbytes, loff_t *ppos);
418 * read_u64() is a shortcut for the common case of returning a
419 * single integer. Use it in place of read()
421 u64 (*read_u64)(struct cgroup *cgrp, struct cftype *cft);
423 * read_s64() is a signed version of read_u64()
425 s64 (*read_s64)(struct cgroup *cgrp, struct cftype *cft);
427 * read_map() is used for defining a map of key/value
428 * pairs. It should call cb->fill(cb, key, value) for each
429 * entry. The key/value pairs (and their ordering) should not
430 * change between reboots.
432 int (*read_map)(struct cgroup *cgrp, struct cftype *cft,
433 struct cgroup_map_cb *cb);
435 * read_seq_string() is used for outputting a simple sequence
438 int (*read_seq_string)(struct cgroup *cgrp, struct cftype *cft,
441 ssize_t (*write)(struct cgroup *cgrp, struct cftype *cft,
443 const char __user *buf, size_t nbytes, loff_t *ppos);
446 * write_u64() is a shortcut for the common case of accepting
447 * a single integer (as parsed by simple_strtoull) from
448 * userspace. Use in place of write(); return 0 or error.
450 int (*write_u64)(struct cgroup *cgrp, struct cftype *cft, u64 val);
452 * write_s64() is a signed version of write_u64()
454 int (*write_s64)(struct cgroup *cgrp, struct cftype *cft, s64 val);
457 * write_string() is passed a nul-terminated kernelspace
458 * buffer of maximum length determined by max_write_len.
459 * Returns 0 or -ve error code.
461 int (*write_string)(struct cgroup *cgrp, struct cftype *cft,
464 * trigger() callback can be used to get some kick from the
465 * userspace, when the actual string written is not important
466 * at all. The private field can be used to determine the
467 * kick type for multiplexing.
469 int (*trigger)(struct cgroup *cgrp, unsigned int event);
471 int (*release)(struct inode *inode, struct file *file);
474 * register_event() callback will be used to add new userspace
475 * waiter for changes related to the cftype. Implement it if
476 * you want to provide this functionality. Use eventfd_signal()
477 * on eventfd to send notification to userspace.
479 int (*register_event)(struct cgroup *cgrp, struct cftype *cft,
480 struct eventfd_ctx *eventfd, const char *args);
482 * unregister_event() callback will be called when userspace
483 * closes the eventfd or on cgroup removing.
484 * This callback must be implemented, if you want provide
485 * notification functionality.
487 void (*unregister_event)(struct cgroup *cgrp, struct cftype *cft,
488 struct eventfd_ctx *eventfd);
492 * cftype_sets describe cftypes belonging to a subsystem and are chained at
493 * cgroup_subsys->cftsets. Each cftset points to an array of cftypes
494 * terminated by zero length name.
497 struct list_head node; /* chained at subsys->cftsets */
501 struct cgroup_scanner {
503 int (*test_task)(struct task_struct *p, struct cgroup_scanner *scan);
504 void (*process_task)(struct task_struct *p,
505 struct cgroup_scanner *scan);
506 struct ptr_heap *heap;
511 * See the comment above CGRP_ROOT_SANE_BEHAVIOR for details. This
512 * function can be called as long as @cgrp is accessible.
514 static inline bool cgroup_sane_behavior(const struct cgroup *cgrp)
516 return cgrp->root->flags & CGRP_ROOT_SANE_BEHAVIOR;
519 /* Caller should hold rcu_read_lock() */
520 static inline const char *cgroup_name(const struct cgroup *cgrp)
522 return rcu_dereference(cgrp->name)->name;
525 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
526 int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
528 bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
530 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
531 int task_cgroup_path_from_hierarchy(struct task_struct *task, int hierarchy_id,
532 char *buf, size_t buflen);
534 int cgroup_task_count(const struct cgroup *cgrp);
537 * Control Group taskset, used to pass around set of tasks to cgroup_subsys
540 struct cgroup_taskset;
541 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
542 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
543 struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset);
544 int cgroup_taskset_size(struct cgroup_taskset *tset);
547 * cgroup_taskset_for_each - iterate cgroup_taskset
548 * @task: the loop cursor
549 * @skip_cgrp: skip if task's cgroup matches this, %NULL to iterate through all
550 * @tset: taskset to iterate
552 #define cgroup_taskset_for_each(task, skip_cgrp, tset) \
553 for ((task) = cgroup_taskset_first((tset)); (task); \
554 (task) = cgroup_taskset_next((tset))) \
555 if (!(skip_cgrp) || \
556 cgroup_taskset_cur_cgroup((tset)) != (skip_cgrp))
559 * Control Group subsystem type.
560 * See Documentation/cgroups/cgroups.txt for details
563 struct cgroup_subsys {
564 struct cgroup_subsys_state *(*css_alloc)(struct cgroup *cgrp);
565 int (*css_online)(struct cgroup *cgrp);
566 void (*css_offline)(struct cgroup *cgrp);
567 void (*css_free)(struct cgroup *cgrp);
569 int (*can_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
570 void (*cancel_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
571 void (*attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
572 void (*fork)(struct task_struct *task);
573 void (*exit)(struct cgroup *cgrp, struct cgroup *old_cgrp,
574 struct task_struct *task);
575 void (*bind)(struct cgroup *root);
581 * True if this subsys uses ID. ID is not available before cgroup_init()
582 * (not available in early_init time.)
587 * If %false, this subsystem is properly hierarchical -
588 * configuration, resource accounting and restriction on a parent
589 * cgroup cover those of its children. If %true, hierarchy support
590 * is broken in some ways - some subsystems ignore hierarchy
591 * completely while others are only implemented half-way.
593 * It's now disallowed to create nested cgroups if the subsystem is
594 * broken and cgroup core will emit a warning message on such
595 * cases. Eventually, all subsystems will be made properly
596 * hierarchical and this will go away.
598 bool broken_hierarchy;
599 bool warned_broken_hierarchy;
601 #define MAX_CGROUP_TYPE_NAMELEN 32
605 * Link to parent, and list entry in parent's children.
606 * Protected by cgroup_lock()
608 struct cgroupfs_root *root;
609 struct list_head sibling;
610 /* used when use_id == true */
614 /* list of cftype_sets */
615 struct list_head cftsets;
617 /* base cftypes, automatically [de]registered with subsys itself */
618 struct cftype *base_cftypes;
619 struct cftype_set base_cftset;
621 /* should be defined only by modular subsystems */
622 struct module *module;
625 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
626 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
627 #include <linux/cgroup_subsys.h>
628 #undef IS_SUBSYS_ENABLED
631 static inline struct cgroup_subsys_state *cgroup_subsys_state(
632 struct cgroup *cgrp, int subsys_id)
634 return cgrp->subsys[subsys_id];
638 * function to get the cgroup_subsys_state which allows for extra
639 * rcu_dereference_check() conditions, such as locks used during the
640 * cgroup_subsys::attach() methods.
642 #ifdef CONFIG_PROVE_RCU
643 extern struct mutex cgroup_mutex;
644 #define task_subsys_state_check(task, subsys_id, __c) \
645 rcu_dereference_check((task)->cgroups->subsys[(subsys_id)], \
646 lockdep_is_held(&(task)->alloc_lock) || \
647 lockdep_is_held(&cgroup_mutex) || (__c))
649 #define task_subsys_state_check(task, subsys_id, __c) \
650 rcu_dereference((task)->cgroups->subsys[(subsys_id)])
653 static inline struct cgroup_subsys_state *
654 task_subsys_state(struct task_struct *task, int subsys_id)
656 return task_subsys_state_check(task, subsys_id, false);
659 static inline struct cgroup* task_cgroup(struct task_struct *task,
662 return task_subsys_state(task, subsys_id)->cgroup;
665 struct cgroup *cgroup_next_sibling(struct cgroup *pos);
668 * cgroup_for_each_child - iterate through children of a cgroup
669 * @pos: the cgroup * to use as the loop cursor
670 * @cgrp: cgroup whose children to walk
672 * Walk @cgrp's children. Must be called under rcu_read_lock(). A child
673 * cgroup which hasn't finished ->css_online() or already has finished
674 * ->css_offline() may show up during traversal and it's each subsystem's
675 * responsibility to verify that each @pos is alive.
677 * If a subsystem synchronizes against the parent in its ->css_online() and
678 * before starting iterating, a cgroup which finished ->css_online() is
679 * guaranteed to be visible in the future iterations.
681 * It is allowed to temporarily drop RCU read lock during iteration. The
682 * caller is responsible for ensuring that @pos remains accessible until
683 * the start of the next iteration by, for example, bumping the css refcnt.
685 #define cgroup_for_each_child(pos, cgrp) \
686 for ((pos) = list_first_or_null_rcu(&(cgrp)->children, \
687 struct cgroup, sibling); \
688 (pos); (pos) = cgroup_next_sibling((pos)))
690 struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
691 struct cgroup *cgroup);
692 struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos);
695 * cgroup_for_each_descendant_pre - pre-order walk of a cgroup's descendants
696 * @pos: the cgroup * to use as the loop cursor
697 * @cgroup: cgroup whose descendants to walk
699 * Walk @cgroup's descendants. Must be called under rcu_read_lock(). A
700 * descendant cgroup which hasn't finished ->css_online() or already has
701 * finished ->css_offline() may show up during traversal and it's each
702 * subsystem's responsibility to verify that each @pos is alive.
704 * If a subsystem synchronizes against the parent in its ->css_online() and
705 * before starting iterating, and synchronizes against @pos on each
706 * iteration, any descendant cgroup which finished ->css_online() is
707 * guaranteed to be visible in the future iterations.
709 * In other words, the following guarantees that a descendant can't escape
710 * state updates of its ancestors.
714 * Lock @cgrp->parent and @cgrp;
715 * Inherit state from @cgrp->parent;
719 * my_update_state(@cgrp)
722 * Update @cgrp's state;
725 * cgroup_for_each_descendant_pre(@pos, @cgrp) {
727 * Verify @pos is alive and inherit state from @pos->parent;
732 * As long as the inheriting step, including checking the parent state, is
733 * enclosed inside @pos locking, double-locking the parent isn't necessary
734 * while inheriting. The state update to the parent is guaranteed to be
735 * visible by walking order and, as long as inheriting operations to the
736 * same @pos are atomic to each other, multiple updates racing each other
737 * still result in the correct state. It's guaranateed that at least one
738 * inheritance happens for any cgroup after the latest update to its
741 * If checking parent's state requires locking the parent, each inheriting
742 * iteration should lock and unlock both @pos->parent and @pos.
744 * Alternatively, a subsystem may choose to use a single global lock to
745 * synchronize ->css_online() and ->css_offline() against tree-walking
748 * It is allowed to temporarily drop RCU read lock during iteration. The
749 * caller is responsible for ensuring that @pos remains accessible until
750 * the start of the next iteration by, for example, bumping the css refcnt.
752 #define cgroup_for_each_descendant_pre(pos, cgroup) \
753 for (pos = cgroup_next_descendant_pre(NULL, (cgroup)); (pos); \
754 pos = cgroup_next_descendant_pre((pos), (cgroup)))
756 struct cgroup *cgroup_next_descendant_post(struct cgroup *pos,
757 struct cgroup *cgroup);
760 * cgroup_for_each_descendant_post - post-order walk of a cgroup's descendants
761 * @pos: the cgroup * to use as the loop cursor
762 * @cgroup: cgroup whose descendants to walk
764 * Similar to cgroup_for_each_descendant_pre() but performs post-order
765 * traversal instead. Note that the walk visibility guarantee described in
766 * pre-order walk doesn't apply the same to post-order walks.
768 #define cgroup_for_each_descendant_post(pos, cgroup) \
769 for (pos = cgroup_next_descendant_post(NULL, (cgroup)); (pos); \
770 pos = cgroup_next_descendant_post((pos), (cgroup)))
772 /* A cgroup_iter should be treated as an opaque object */
774 struct list_head *cset_link;
775 struct list_head *task;
779 * To iterate across the tasks in a cgroup:
781 * 1) call cgroup_iter_start to initialize an iterator
783 * 2) call cgroup_iter_next() to retrieve member tasks until it
784 * returns NULL or until you want to end the iteration
786 * 3) call cgroup_iter_end() to destroy the iterator.
788 * Or, call cgroup_scan_tasks() to iterate through every task in a
789 * cgroup - cgroup_scan_tasks() holds the css_set_lock when calling
790 * the test_task() callback, but not while calling the process_task()
793 void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it);
794 struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
795 struct cgroup_iter *it);
796 void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it);
797 int cgroup_scan_tasks(struct cgroup_scanner *scan);
798 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
799 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
802 * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
803 * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
804 * CSS ID is assigned at cgroup allocation (create) automatically
805 * and removed when subsys calls free_css_id() function. This is because
806 * the lifetime of cgroup_subsys_state is subsys's matter.
808 * Looking up and scanning function should be called under rcu_read_lock().
809 * Taking cgroup_mutex is not necessary for following calls.
810 * But the css returned by this routine can be "not populated yet" or "being
811 * destroyed". The caller should check css and cgroup's status.
815 * Typically Called at ->destroy(), or somewhere the subsys frees
816 * cgroup_subsys_state.
818 void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
820 /* Find a cgroup_subsys_state which has given ID */
822 struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id);
824 /* Returns true if root is ancestor of cg */
825 bool css_is_ancestor(struct cgroup_subsys_state *cg,
826 const struct cgroup_subsys_state *root);
828 /* Get id and depth of css */
829 unsigned short css_id(struct cgroup_subsys_state *css);
830 struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id);
832 #else /* !CONFIG_CGROUPS */
834 static inline int cgroup_init_early(void) { return 0; }
835 static inline int cgroup_init(void) { return 0; }
836 static inline void cgroup_fork(struct task_struct *p) {}
837 static inline void cgroup_post_fork(struct task_struct *p) {}
838 static inline void cgroup_exit(struct task_struct *p, int callbacks) {}
840 static inline int cgroupstats_build(struct cgroupstats *stats,
841 struct dentry *dentry)
846 /* No cgroups - nothing to do */
847 static inline int cgroup_attach_task_all(struct task_struct *from,
848 struct task_struct *t)
853 #endif /* !CONFIG_CGROUPS */
855 #endif /* _LINUX_CGROUP_H */