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>
33 extern int cgroup_init_early(void);
34 extern int cgroup_init(void);
35 extern void cgroup_fork(struct task_struct *p);
36 extern void cgroup_post_fork(struct task_struct *p);
37 extern void cgroup_exit(struct task_struct *p, int run_callbacks);
38 extern int cgroupstats_build(struct cgroupstats *stats,
39 struct dentry *dentry);
40 extern int cgroup_load_subsys(struct cgroup_subsys *ss);
41 extern void cgroup_unload_subsys(struct cgroup_subsys *ss);
43 extern int proc_cgroup_show(struct seq_file *, void *);
46 * Define the enumeration of all cgroup subsystems.
48 * We define ids for builtin subsystems and then modular ones.
50 #define SUBSYS(_x) _x ## _subsys_id,
51 enum cgroup_subsys_id {
52 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
53 #include <linux/cgroup_subsys.h>
54 #undef IS_SUBSYS_ENABLED
55 CGROUP_BUILTIN_SUBSYS_COUNT,
57 __CGROUP_SUBSYS_TEMP_PLACEHOLDER = CGROUP_BUILTIN_SUBSYS_COUNT - 1,
59 #define IS_SUBSYS_ENABLED(option) IS_MODULE(option)
60 #include <linux/cgroup_subsys.h>
61 #undef IS_SUBSYS_ENABLED
66 /* Per-subsystem/per-cgroup state maintained by the system. */
67 struct cgroup_subsys_state {
69 * The cgroup that this subsystem is attached to. Useful
70 * for subsystems that want to know about the cgroup
73 struct cgroup *cgroup;
76 * State maintained by the cgroup system to allow subsystems
77 * to be "busy". Should be accessed via css_get(),
78 * css_tryget() and css_put().
84 /* ID for this css, if possible */
85 struct css_id __rcu *id;
87 /* Used to put @cgroup->dentry on the last css_put() */
88 struct work_struct dput_work;
91 /* bits in struct cgroup_subsys_state flags field */
93 CSS_ROOT = (1 << 0), /* this CSS is the root of the subsystem */
94 CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */
97 /* Caller must verify that the css is not for root cgroup */
98 static inline void __css_get(struct cgroup_subsys_state *css, int count)
100 atomic_add(count, &css->refcnt);
104 * Call css_get() to hold a reference on the css; it can be used
105 * for a reference obtained via:
106 * - an existing ref-counted reference to the css
107 * - task->cgroups for a locked task
110 static inline void css_get(struct cgroup_subsys_state *css)
112 /* We don't need to reference count the root state */
113 if (!(css->flags & CSS_ROOT))
118 * Call css_tryget() to take a reference on a css if your existing
119 * (known-valid) reference isn't already ref-counted. Returns false if
120 * the css has been destroyed.
123 extern bool __css_tryget(struct cgroup_subsys_state *css);
124 static inline bool css_tryget(struct cgroup_subsys_state *css)
126 if (css->flags & CSS_ROOT)
128 return __css_tryget(css);
132 * css_put() should be called to release a reference taken by
133 * css_get() or css_tryget()
136 extern void __css_put(struct cgroup_subsys_state *css);
137 static inline void css_put(struct cgroup_subsys_state *css)
139 if (!(css->flags & CSS_ROOT))
143 /* bits in struct cgroup flags field */
145 /* Control Group is dead */
148 * Control Group has previously had a child cgroup or a task,
149 * but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
152 /* Control Group requires release notifications to userspace */
153 CGRP_NOTIFY_ON_RELEASE,
155 * Clone the parent's configuration when creating a new child
156 * cpuset cgroup. For historical reasons, this option can be
157 * specified at mount time and thus is implemented here.
159 CGRP_CPUSET_CLONE_CHILDREN,
160 /* see the comment above CGRP_ROOT_SANE_BEHAVIOR for details */
165 struct rcu_head rcu_head;
170 unsigned long flags; /* "unsigned long" so bitops work */
173 * count users of this cgroup. >0 means busy, but doesn't
174 * necessarily indicate the number of tasks in the cgroup
178 int id; /* ida allocated in-hierarchy ID */
181 * We link our 'sibling' struct into our parent's 'children'.
182 * Our children link their 'sibling' into our 'children'.
184 struct list_head sibling; /* my parent's children */
185 struct list_head children; /* my children */
186 struct list_head files; /* my files */
188 struct cgroup *parent; /* my parent */
189 struct dentry *dentry; /* cgroup fs entry, RCU protected */
192 * Monotonically increasing unique serial number which defines a
193 * uniform order among all cgroups. It's guaranteed that all
194 * ->children lists are in the ascending order of ->serial_nr.
195 * It's used to allow interrupting and resuming iterations.
200 * This is a copy of dentry->d_name, and it's needed because
201 * we can't use dentry->d_name in cgroup_path().
203 * You must acquire rcu_read_lock() to access cgrp->name, and
204 * the only place that can change it is rename(), which is
205 * protected by parent dir's i_mutex.
207 * Normally you should use cgroup_name() wrapper rather than
208 * access it directly.
210 struct cgroup_name __rcu *name;
212 /* Private pointers for each registered subsystem */
213 struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
215 struct cgroupfs_root *root;
218 * List of cg_cgroup_links pointing at css_sets with
219 * tasks in this cgroup. Protected by css_set_lock
221 struct list_head css_sets;
223 struct list_head allcg_node; /* cgroupfs_root->allcg_list */
224 struct list_head cft_q_node; /* used during cftype add/rm */
227 * Linked list running through all cgroups that can
228 * potentially be reaped by the release agent. Protected by
231 struct list_head release_list;
234 * list of pidlists, up to two for each namespace (one for procs, one
235 * for tasks); created on demand.
237 struct list_head pidlists;
238 struct mutex pidlist_mutex;
240 /* For RCU-protected deletion */
241 struct rcu_head rcu_head;
242 struct work_struct free_work;
244 /* List of events which userspace want to receive */
245 struct list_head event_list;
246 spinlock_t event_list_lock;
248 /* directory xattrs */
249 struct simple_xattrs xattrs;
252 #define MAX_CGROUP_ROOT_NAMELEN 64
254 /* cgroupfs_root->flags */
257 * Unfortunately, cgroup core and various controllers are riddled
258 * with idiosyncrasies and pointless options. The following flag,
259 * when set, will force sane behavior - some options are forced on,
260 * others are disallowed, and some controllers will change their
261 * hierarchical or other behaviors.
263 * The set of behaviors affected by this flag are still being
264 * determined and developed and the mount option for this flag is
265 * prefixed with __DEVEL__. The prefix will be dropped once we
266 * reach the point where all behaviors are compatible with the
267 * planned unified hierarchy, which will automatically turn on this
270 * The followings are the behaviors currently affected this flag.
272 * - Mount options "noprefix" and "clone_children" are disallowed.
273 * Also, cgroupfs file cgroup.clone_children is not created.
275 * - When mounting an existing superblock, mount options should
278 * - Remount is disallowed.
280 * - cpuset: tasks will be kept in empty cpusets when hotplug happens
281 * and take masks of ancestors with non-empty cpus/mems, instead of
282 * being moved to an ancestor.
284 * - cpuset: a task can be moved into an empty cpuset, and again it
285 * takes masks of ancestors.
287 * - memcg: use_hierarchy is on by default and the cgroup file for
288 * the flag is not created.
290 * The followings are planned changes.
292 * - release_agent will be disallowed once replacement notification
293 * mechanism is implemented.
295 CGRP_ROOT_SANE_BEHAVIOR = (1 << 0),
297 CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
298 CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
302 * A cgroupfs_root represents the root of a cgroup hierarchy, and may be
303 * associated with a superblock to form an active hierarchy. This is
304 * internal to cgroup core. Don't access directly from controllers.
306 struct cgroupfs_root {
307 struct super_block *sb;
310 * The bitmask of subsystems intended to be attached to this
313 unsigned long subsys_mask;
315 /* Unique id for this hierarchy. */
318 /* The bitmask of subsystems currently attached to this hierarchy */
319 unsigned long actual_subsys_mask;
321 /* A list running through the attached subsystems */
322 struct list_head subsys_list;
324 /* The root cgroup for this hierarchy */
325 struct cgroup top_cgroup;
327 /* Tracks how many cgroups are currently defined in hierarchy.*/
328 int number_of_cgroups;
330 /* A list running through the active hierarchies */
331 struct list_head root_list;
333 /* All cgroups on this root, cgroup_mutex protected */
334 struct list_head allcg_list;
336 /* Hierarchy-specific flags */
339 /* IDs for cgroups in this hierarchy */
340 struct ida cgroup_ida;
342 /* The path to use for release notifications. */
343 char release_agent_path[PATH_MAX];
345 /* The name for this hierarchy - may be empty */
346 char name[MAX_CGROUP_ROOT_NAMELEN];
350 * A css_set is a structure holding pointers to a set of
351 * cgroup_subsys_state objects. This saves space in the task struct
352 * object and speeds up fork()/exit(), since a single inc/dec and a
353 * list_add()/del() can bump the reference count on the entire cgroup
359 /* Reference count */
363 * List running through all cgroup groups in the same hash
364 * slot. Protected by css_set_lock
366 struct hlist_node hlist;
369 * List running through all tasks using this cgroup
370 * group. Protected by css_set_lock
372 struct list_head tasks;
375 * List of cg_cgroup_link objects on link chains from
376 * cgroups referenced from this css_set. Protected by
379 struct list_head cg_links;
382 * Set of subsystem states, one for each subsystem. This array
383 * is immutable after creation apart from the init_css_set
384 * during subsystem registration (at boot time) and modular subsystem
387 struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
389 /* For RCU-protected deletion */
390 struct rcu_head rcu_head;
394 * cgroup_map_cb is an abstract callback API for reporting map-valued
398 struct cgroup_map_cb {
399 int (*fill)(struct cgroup_map_cb *cb, const char *key, u64 value);
404 * struct cftype: handler definitions for cgroup control files
406 * When reading/writing to a file:
407 * - the cgroup to use is file->f_dentry->d_parent->d_fsdata
408 * - the 'cftype' of the file is file->f_dentry->d_fsdata
412 #define CFTYPE_ONLY_ON_ROOT (1U << 0) /* only create on root cg */
413 #define CFTYPE_NOT_ON_ROOT (1U << 1) /* don't create on root cg */
414 #define CFTYPE_INSANE (1U << 2) /* don't create if sane_behavior */
416 #define MAX_CFTYPE_NAME 64
420 * By convention, the name should begin with the name of the
421 * subsystem, followed by a period. Zero length string indicates
422 * end of cftype array.
424 char name[MAX_CFTYPE_NAME];
427 * If not 0, file mode is set to this value, otherwise it will
428 * be figured out automatically
433 * If non-zero, defines the maximum length of string that can
434 * be passed to write_string; defaults to 64
436 size_t max_write_len;
441 int (*open)(struct inode *inode, struct file *file);
442 ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
444 char __user *buf, size_t nbytes, loff_t *ppos);
446 * read_u64() is a shortcut for the common case of returning a
447 * single integer. Use it in place of read()
449 u64 (*read_u64)(struct cgroup *cgrp, struct cftype *cft);
451 * read_s64() is a signed version of read_u64()
453 s64 (*read_s64)(struct cgroup *cgrp, struct cftype *cft);
455 * read_map() is used for defining a map of key/value
456 * pairs. It should call cb->fill(cb, key, value) for each
457 * entry. The key/value pairs (and their ordering) should not
458 * change between reboots.
460 int (*read_map)(struct cgroup *cont, struct cftype *cft,
461 struct cgroup_map_cb *cb);
463 * read_seq_string() is used for outputting a simple sequence
466 int (*read_seq_string)(struct cgroup *cont, struct cftype *cft,
469 ssize_t (*write)(struct cgroup *cgrp, struct cftype *cft,
471 const char __user *buf, size_t nbytes, loff_t *ppos);
474 * write_u64() is a shortcut for the common case of accepting
475 * a single integer (as parsed by simple_strtoull) from
476 * userspace. Use in place of write(); return 0 or error.
478 int (*write_u64)(struct cgroup *cgrp, struct cftype *cft, u64 val);
480 * write_s64() is a signed version of write_u64()
482 int (*write_s64)(struct cgroup *cgrp, struct cftype *cft, s64 val);
485 * write_string() is passed a nul-terminated kernelspace
486 * buffer of maximum length determined by max_write_len.
487 * Returns 0 or -ve error code.
489 int (*write_string)(struct cgroup *cgrp, struct cftype *cft,
492 * trigger() callback can be used to get some kick from the
493 * userspace, when the actual string written is not important
494 * at all. The private field can be used to determine the
495 * kick type for multiplexing.
497 int (*trigger)(struct cgroup *cgrp, unsigned int event);
499 int (*release)(struct inode *inode, struct file *file);
502 * register_event() callback will be used to add new userspace
503 * waiter for changes related to the cftype. Implement it if
504 * you want to provide this functionality. Use eventfd_signal()
505 * on eventfd to send notification to userspace.
507 int (*register_event)(struct cgroup *cgrp, struct cftype *cft,
508 struct eventfd_ctx *eventfd, const char *args);
510 * unregister_event() callback will be called when userspace
511 * closes the eventfd or on cgroup removing.
512 * This callback must be implemented, if you want provide
513 * notification functionality.
515 void (*unregister_event)(struct cgroup *cgrp, struct cftype *cft,
516 struct eventfd_ctx *eventfd);
520 * cftype_sets describe cftypes belonging to a subsystem and are chained at
521 * cgroup_subsys->cftsets. Each cftset points to an array of cftypes
522 * terminated by zero length name.
525 struct list_head node; /* chained at subsys->cftsets */
529 struct cgroup_scanner {
531 int (*test_task)(struct task_struct *p, struct cgroup_scanner *scan);
532 void (*process_task)(struct task_struct *p,
533 struct cgroup_scanner *scan);
534 struct ptr_heap *heap;
539 * See the comment above CGRP_ROOT_SANE_BEHAVIOR for details. This
540 * function can be called as long as @cgrp is accessible.
542 static inline bool cgroup_sane_behavior(const struct cgroup *cgrp)
544 return cgrp->root->flags & CGRP_ROOT_SANE_BEHAVIOR;
547 /* Caller should hold rcu_read_lock() */
548 static inline const char *cgroup_name(const struct cgroup *cgrp)
550 return rcu_dereference(cgrp->name)->name;
553 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
554 int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
556 bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
558 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
559 int task_cgroup_path_from_hierarchy(struct task_struct *task, int hierarchy_id,
560 char *buf, size_t buflen);
562 int cgroup_task_count(const struct cgroup *cgrp);
565 * Control Group taskset, used to pass around set of tasks to cgroup_subsys
568 struct cgroup_taskset;
569 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
570 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
571 struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset);
572 int cgroup_taskset_size(struct cgroup_taskset *tset);
575 * cgroup_taskset_for_each - iterate cgroup_taskset
576 * @task: the loop cursor
577 * @skip_cgrp: skip if task's cgroup matches this, %NULL to iterate through all
578 * @tset: taskset to iterate
580 #define cgroup_taskset_for_each(task, skip_cgrp, tset) \
581 for ((task) = cgroup_taskset_first((tset)); (task); \
582 (task) = cgroup_taskset_next((tset))) \
583 if (!(skip_cgrp) || \
584 cgroup_taskset_cur_cgroup((tset)) != (skip_cgrp))
587 * Control Group subsystem type.
588 * See Documentation/cgroups/cgroups.txt for details
591 struct cgroup_subsys {
592 struct cgroup_subsys_state *(*css_alloc)(struct cgroup *cgrp);
593 int (*css_online)(struct cgroup *cgrp);
594 void (*css_offline)(struct cgroup *cgrp);
595 void (*css_free)(struct cgroup *cgrp);
597 int (*can_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
598 void (*cancel_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
599 void (*attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
600 void (*fork)(struct task_struct *task);
601 void (*exit)(struct cgroup *cgrp, struct cgroup *old_cgrp,
602 struct task_struct *task);
603 void (*bind)(struct cgroup *root);
609 * True if this subsys uses ID. ID is not available before cgroup_init()
610 * (not available in early_init time.)
615 * If %false, this subsystem is properly hierarchical -
616 * configuration, resource accounting and restriction on a parent
617 * cgroup cover those of its children. If %true, hierarchy support
618 * is broken in some ways - some subsystems ignore hierarchy
619 * completely while others are only implemented half-way.
621 * It's now disallowed to create nested cgroups if the subsystem is
622 * broken and cgroup core will emit a warning message on such
623 * cases. Eventually, all subsystems will be made properly
624 * hierarchical and this will go away.
626 bool broken_hierarchy;
627 bool warned_broken_hierarchy;
629 #define MAX_CGROUP_TYPE_NAMELEN 32
633 * Link to parent, and list entry in parent's children.
634 * Protected by cgroup_lock()
636 struct cgroupfs_root *root;
637 struct list_head sibling;
638 /* used when use_id == true */
642 /* list of cftype_sets */
643 struct list_head cftsets;
645 /* base cftypes, automatically [de]registered with subsys itself */
646 struct cftype *base_cftypes;
647 struct cftype_set base_cftset;
649 /* should be defined only by modular subsystems */
650 struct module *module;
653 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
654 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
655 #include <linux/cgroup_subsys.h>
656 #undef IS_SUBSYS_ENABLED
659 static inline struct cgroup_subsys_state *cgroup_subsys_state(
660 struct cgroup *cgrp, int subsys_id)
662 return cgrp->subsys[subsys_id];
666 * function to get the cgroup_subsys_state which allows for extra
667 * rcu_dereference_check() conditions, such as locks used during the
668 * cgroup_subsys::attach() methods.
670 #ifdef CONFIG_PROVE_RCU
671 extern struct mutex cgroup_mutex;
672 #define task_subsys_state_check(task, subsys_id, __c) \
673 rcu_dereference_check((task)->cgroups->subsys[(subsys_id)], \
674 lockdep_is_held(&(task)->alloc_lock) || \
675 lockdep_is_held(&cgroup_mutex) || (__c))
677 #define task_subsys_state_check(task, subsys_id, __c) \
678 rcu_dereference((task)->cgroups->subsys[(subsys_id)])
681 static inline struct cgroup_subsys_state *
682 task_subsys_state(struct task_struct *task, int subsys_id)
684 return task_subsys_state_check(task, subsys_id, false);
687 static inline struct cgroup* task_cgroup(struct task_struct *task,
690 return task_subsys_state(task, subsys_id)->cgroup;
693 struct cgroup *cgroup_next_sibling(struct cgroup *pos);
696 * cgroup_for_each_child - iterate through children of a cgroup
697 * @pos: the cgroup * to use as the loop cursor
698 * @cgrp: cgroup whose children to walk
700 * Walk @cgrp's children. Must be called under rcu_read_lock(). A child
701 * cgroup which hasn't finished ->css_online() or already has finished
702 * ->css_offline() may show up during traversal and it's each subsystem's
703 * responsibility to verify that each @pos is alive.
705 * If a subsystem synchronizes against the parent in its ->css_online() and
706 * before starting iterating, a cgroup which finished ->css_online() is
707 * guaranteed to be visible in the future iterations.
709 * It is allowed to temporarily drop RCU read lock during iteration. The
710 * caller is responsible for ensuring that @pos remains accessible until
711 * the start of the next iteration by, for example, bumping the css refcnt.
713 #define cgroup_for_each_child(pos, cgrp) \
714 for ((pos) = list_first_or_null_rcu(&(cgrp)->children, \
715 struct cgroup, sibling); \
716 (pos); (pos) = cgroup_next_sibling((pos)))
718 struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
719 struct cgroup *cgroup);
720 struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos);
723 * cgroup_for_each_descendant_pre - pre-order walk of a cgroup's descendants
724 * @pos: the cgroup * to use as the loop cursor
725 * @cgroup: cgroup whose descendants to walk
727 * Walk @cgroup's descendants. Must be called under rcu_read_lock(). A
728 * descendant cgroup which hasn't finished ->css_online() or already has
729 * finished ->css_offline() may show up during traversal and it's each
730 * subsystem's responsibility to verify that each @pos is alive.
732 * If a subsystem synchronizes against the parent in its ->css_online() and
733 * before starting iterating, and synchronizes against @pos on each
734 * iteration, any descendant cgroup which finished ->css_online() is
735 * guaranteed to be visible in the future iterations.
737 * In other words, the following guarantees that a descendant can't escape
738 * state updates of its ancestors.
742 * Lock @cgrp->parent and @cgrp;
743 * Inherit state from @cgrp->parent;
747 * my_update_state(@cgrp)
750 * Update @cgrp's state;
753 * cgroup_for_each_descendant_pre(@pos, @cgrp) {
755 * Verify @pos is alive and inherit state from @pos->parent;
760 * As long as the inheriting step, including checking the parent state, is
761 * enclosed inside @pos locking, double-locking the parent isn't necessary
762 * while inheriting. The state update to the parent is guaranteed to be
763 * visible by walking order and, as long as inheriting operations to the
764 * same @pos are atomic to each other, multiple updates racing each other
765 * still result in the correct state. It's guaranateed that at least one
766 * inheritance happens for any cgroup after the latest update to its
769 * If checking parent's state requires locking the parent, each inheriting
770 * iteration should lock and unlock both @pos->parent and @pos.
772 * Alternatively, a subsystem may choose to use a single global lock to
773 * synchronize ->css_online() and ->css_offline() against tree-walking
776 * It is allowed to temporarily drop RCU read lock during iteration. The
777 * caller is responsible for ensuring that @pos remains accessible until
778 * the start of the next iteration by, for example, bumping the css refcnt.
780 #define cgroup_for_each_descendant_pre(pos, cgroup) \
781 for (pos = cgroup_next_descendant_pre(NULL, (cgroup)); (pos); \
782 pos = cgroup_next_descendant_pre((pos), (cgroup)))
784 struct cgroup *cgroup_next_descendant_post(struct cgroup *pos,
785 struct cgroup *cgroup);
788 * cgroup_for_each_descendant_post - post-order walk of a cgroup's descendants
789 * @pos: the cgroup * to use as the loop cursor
790 * @cgroup: cgroup whose descendants to walk
792 * Similar to cgroup_for_each_descendant_pre() but performs post-order
793 * traversal instead. Note that the walk visibility guarantee described in
794 * pre-order walk doesn't apply the same to post-order walks.
796 #define cgroup_for_each_descendant_post(pos, cgroup) \
797 for (pos = cgroup_next_descendant_post(NULL, (cgroup)); (pos); \
798 pos = cgroup_next_descendant_post((pos), (cgroup)))
800 /* A cgroup_iter should be treated as an opaque object */
802 struct list_head *cg_link;
803 struct list_head *task;
807 * To iterate across the tasks in a cgroup:
809 * 1) call cgroup_iter_start to initialize an iterator
811 * 2) call cgroup_iter_next() to retrieve member tasks until it
812 * returns NULL or until you want to end the iteration
814 * 3) call cgroup_iter_end() to destroy the iterator.
816 * Or, call cgroup_scan_tasks() to iterate through every task in a
817 * cgroup - cgroup_scan_tasks() holds the css_set_lock when calling
818 * the test_task() callback, but not while calling the process_task()
821 void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it);
822 struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
823 struct cgroup_iter *it);
824 void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it);
825 int cgroup_scan_tasks(struct cgroup_scanner *scan);
826 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
827 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
830 * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
831 * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
832 * CSS ID is assigned at cgroup allocation (create) automatically
833 * and removed when subsys calls free_css_id() function. This is because
834 * the lifetime of cgroup_subsys_state is subsys's matter.
836 * Looking up and scanning function should be called under rcu_read_lock().
837 * Taking cgroup_mutex is not necessary for following calls.
838 * But the css returned by this routine can be "not populated yet" or "being
839 * destroyed". The caller should check css and cgroup's status.
843 * Typically Called at ->destroy(), or somewhere the subsys frees
844 * cgroup_subsys_state.
846 void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
848 /* Find a cgroup_subsys_state which has given ID */
850 struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id);
852 /* Returns true if root is ancestor of cg */
853 bool css_is_ancestor(struct cgroup_subsys_state *cg,
854 const struct cgroup_subsys_state *root);
856 /* Get id and depth of css */
857 unsigned short css_id(struct cgroup_subsys_state *css);
858 unsigned short css_depth(struct cgroup_subsys_state *css);
859 struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id);
861 #else /* !CONFIG_CGROUPS */
863 static inline int cgroup_init_early(void) { return 0; }
864 static inline int cgroup_init(void) { return 0; }
865 static inline void cgroup_fork(struct task_struct *p) {}
866 static inline void cgroup_post_fork(struct task_struct *p) {}
867 static inline void cgroup_exit(struct task_struct *p, int callbacks) {}
869 static inline int cgroupstats_build(struct cgroupstats *stats,
870 struct dentry *dentry)
875 /* No cgroups - nothing to do */
876 static inline int cgroup_attach_task_all(struct task_struct *from,
877 struct task_struct *t)
882 #endif /* !CONFIG_CGROUPS */
884 #endif /* _LINUX_CGROUP_H */