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>
32 extern int cgroup_init_early(void);
33 extern int cgroup_init(void);
34 extern void cgroup_fork(struct task_struct
*p
);
35 extern void cgroup_post_fork(struct task_struct
*p
);
36 extern void cgroup_exit(struct task_struct
*p
, int run_callbacks
);
37 extern int cgroupstats_build(struct cgroupstats
*stats
,
38 struct dentry
*dentry
);
39 extern int cgroup_load_subsys(struct cgroup_subsys
*ss
);
40 extern void cgroup_unload_subsys(struct cgroup_subsys
*ss
);
42 extern const struct file_operations proc_cgroup_operations
;
45 * Define the enumeration of all cgroup subsystems.
47 * We define ids for builtin subsystems and then modular ones.
49 #define SUBSYS(_x) _x ## _subsys_id,
50 enum cgroup_subsys_id
{
51 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
52 #include <linux/cgroup_subsys.h>
53 #undef IS_SUBSYS_ENABLED
54 CGROUP_BUILTIN_SUBSYS_COUNT
,
56 __CGROUP_SUBSYS_TEMP_PLACEHOLDER
= CGROUP_BUILTIN_SUBSYS_COUNT
- 1,
58 #define IS_SUBSYS_ENABLED(option) IS_MODULE(option)
59 #include <linux/cgroup_subsys.h>
60 #undef IS_SUBSYS_ENABLED
65 /* Per-subsystem/per-cgroup state maintained by the system. */
66 struct cgroup_subsys_state
{
68 * The cgroup that this subsystem is attached to. Useful
69 * for subsystems that want to know about the cgroup
72 struct cgroup
*cgroup
;
75 * State maintained by the cgroup system to allow subsystems
76 * to be "busy". Should be accessed via css_get(),
77 * css_tryget() and css_put().
83 /* ID for this css, if possible */
84 struct css_id __rcu
*id
;
86 /* Used to put @cgroup->dentry on the last css_put() */
87 struct work_struct dput_work
;
90 /* bits in struct cgroup_subsys_state flags field */
92 CSS_ROOT
= (1 << 0), /* this CSS is the root of the subsystem */
93 CSS_ONLINE
= (1 << 1), /* between ->css_online() and ->css_offline() */
96 /* Caller must verify that the css is not for root cgroup */
97 static inline void __css_get(struct cgroup_subsys_state
*css
, int count
)
99 atomic_add(count
, &css
->refcnt
);
103 * Call css_get() to hold a reference on the css; it can be used
104 * for a reference obtained via:
105 * - an existing ref-counted reference to the css
106 * - task->cgroups for a locked task
109 static inline void css_get(struct cgroup_subsys_state
*css
)
111 /* We don't need to reference count the root state */
112 if (!(css
->flags
& CSS_ROOT
))
117 * Call css_tryget() to take a reference on a css if your existing
118 * (known-valid) reference isn't already ref-counted. Returns false if
119 * the css has been destroyed.
122 extern bool __css_tryget(struct cgroup_subsys_state
*css
);
123 static inline bool css_tryget(struct cgroup_subsys_state
*css
)
125 if (css
->flags
& CSS_ROOT
)
127 return __css_tryget(css
);
131 * css_put() should be called to release a reference taken by
132 * css_get() or css_tryget()
135 extern void __css_put(struct cgroup_subsys_state
*css
);
136 static inline void css_put(struct cgroup_subsys_state
*css
)
138 if (!(css
->flags
& CSS_ROOT
))
142 /* bits in struct cgroup flags field */
144 /* Control Group is dead */
147 * Control Group has previously had a child cgroup or a task,
148 * but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
151 /* Control Group requires release notifications to userspace */
152 CGRP_NOTIFY_ON_RELEASE
,
154 * Clone the parent's configuration when creating a new child
155 * cpuset cgroup. For historical reasons, this option can be
156 * specified at mount time and thus is implemented here.
158 CGRP_CPUSET_CLONE_CHILDREN
,
159 /* see the comment above CGRP_ROOT_SANE_BEHAVIOR for details */
164 struct rcu_head rcu_head
;
169 unsigned long flags
; /* "unsigned long" so bitops work */
172 * count users of this cgroup. >0 means busy, but doesn't
173 * necessarily indicate the number of tasks in the cgroup
177 int id
; /* ida allocated in-hierarchy ID */
180 * We link our 'sibling' struct into our parent's 'children'.
181 * Our children link their 'sibling' into our 'children'.
183 struct list_head sibling
; /* my parent's children */
184 struct list_head children
; /* my children */
185 struct list_head files
; /* my files */
187 struct cgroup
*parent
; /* my parent */
188 struct dentry
*dentry
; /* cgroup fs entry, RCU protected */
191 * This is a copy of dentry->d_name, and it's needed because
192 * we can't use dentry->d_name in cgroup_path().
194 * You must acquire rcu_read_lock() to access cgrp->name, and
195 * the only place that can change it is rename(), which is
196 * protected by parent dir's i_mutex.
198 * Normally you should use cgroup_name() wrapper rather than
199 * access it directly.
201 struct cgroup_name __rcu
*name
;
203 /* Private pointers for each registered subsystem */
204 struct cgroup_subsys_state
*subsys
[CGROUP_SUBSYS_COUNT
];
206 struct cgroupfs_root
*root
;
207 struct cgroup
*top_cgroup
;
210 * List of cg_cgroup_links pointing at css_sets with
211 * tasks in this cgroup. Protected by css_set_lock
213 struct list_head css_sets
;
215 struct list_head allcg_node
; /* cgroupfs_root->allcg_list */
216 struct list_head cft_q_node
; /* used during cftype add/rm */
219 * Linked list running through all cgroups that can
220 * potentially be reaped by the release agent. Protected by
223 struct list_head release_list
;
226 * list of pidlists, up to two for each namespace (one for procs, one
227 * for tasks); created on demand.
229 struct list_head pidlists
;
230 struct mutex pidlist_mutex
;
232 /* For RCU-protected deletion */
233 struct rcu_head rcu_head
;
234 struct work_struct free_work
;
236 /* List of events which userspace want to receive */
237 struct list_head event_list
;
238 spinlock_t event_list_lock
;
240 /* directory xattrs */
241 struct simple_xattrs xattrs
;
244 #define MAX_CGROUP_ROOT_NAMELEN 64
246 /* cgroupfs_root->flags */
249 * Unfortunately, cgroup core and various controllers are riddled
250 * with idiosyncrasies and pointless options. The following flag,
251 * when set, will force sane behavior - some options are forced on,
252 * others are disallowed, and some controllers will change their
253 * hierarchical or other behaviors.
255 * The set of behaviors affected by this flag are still being
256 * determined and developed and the mount option for this flag is
257 * prefixed with __DEVEL__. The prefix will be dropped once we
258 * reach the point where all behaviors are compatible with the
259 * planned unified hierarchy, which will automatically turn on this
262 * The followings are the behaviors currently affected this flag.
264 * - Mount options "noprefix" and "clone_children" are disallowed.
265 * Also, cgroupfs file cgroup.clone_children is not created.
267 * - When mounting an existing superblock, mount options should
270 * - Remount is disallowed.
272 * The followings are planned changes.
274 * - release_agent will be disallowed once replacement notification
275 * mechanism is implemented.
277 CGRP_ROOT_SANE_BEHAVIOR
= (1 << 0),
279 CGRP_ROOT_NOPREFIX
= (1 << 1), /* mounted subsystems have no named prefix */
280 CGRP_ROOT_XATTR
= (1 << 2), /* supports extended attributes */
284 * A cgroupfs_root represents the root of a cgroup hierarchy, and may be
285 * associated with a superblock to form an active hierarchy. This is
286 * internal to cgroup core. Don't access directly from controllers.
288 struct cgroupfs_root
{
289 struct super_block
*sb
;
292 * The bitmask of subsystems intended to be attached to this
295 unsigned long subsys_mask
;
297 /* Unique id for this hierarchy. */
300 /* The bitmask of subsystems currently attached to this hierarchy */
301 unsigned long actual_subsys_mask
;
303 /* A list running through the attached subsystems */
304 struct list_head subsys_list
;
306 /* The root cgroup for this hierarchy */
307 struct cgroup top_cgroup
;
309 /* Tracks how many cgroups are currently defined in hierarchy.*/
310 int number_of_cgroups
;
312 /* A list running through the active hierarchies */
313 struct list_head root_list
;
315 /* All cgroups on this root, cgroup_mutex protected */
316 struct list_head allcg_list
;
318 /* Hierarchy-specific flags */
321 /* IDs for cgroups in this hierarchy */
322 struct ida cgroup_ida
;
324 /* The path to use for release notifications. */
325 char release_agent_path
[PATH_MAX
];
327 /* The name for this hierarchy - may be empty */
328 char name
[MAX_CGROUP_ROOT_NAMELEN
];
332 * A css_set is a structure holding pointers to a set of
333 * cgroup_subsys_state objects. This saves space in the task struct
334 * object and speeds up fork()/exit(), since a single inc/dec and a
335 * list_add()/del() can bump the reference count on the entire cgroup
341 /* Reference count */
345 * List running through all cgroup groups in the same hash
346 * slot. Protected by css_set_lock
348 struct hlist_node hlist
;
351 * List running through all tasks using this cgroup
352 * group. Protected by css_set_lock
354 struct list_head tasks
;
357 * List of cg_cgroup_link objects on link chains from
358 * cgroups referenced from this css_set. Protected by
361 struct list_head cg_links
;
364 * Set of subsystem states, one for each subsystem. This array
365 * is immutable after creation apart from the init_css_set
366 * during subsystem registration (at boot time) and modular subsystem
369 struct cgroup_subsys_state
*subsys
[CGROUP_SUBSYS_COUNT
];
371 /* For RCU-protected deletion */
372 struct rcu_head rcu_head
;
376 * cgroup_map_cb is an abstract callback API for reporting map-valued
380 struct cgroup_map_cb
{
381 int (*fill
)(struct cgroup_map_cb
*cb
, const char *key
, u64 value
);
386 * struct cftype: handler definitions for cgroup control files
388 * When reading/writing to a file:
389 * - the cgroup to use is file->f_dentry->d_parent->d_fsdata
390 * - the 'cftype' of the file is file->f_dentry->d_fsdata
394 #define CFTYPE_ONLY_ON_ROOT (1U << 0) /* only create on root cg */
395 #define CFTYPE_NOT_ON_ROOT (1U << 1) /* don't create on root cg */
396 #define CFTYPE_INSANE (1U << 2) /* don't create if sane_behavior */
398 #define MAX_CFTYPE_NAME 64
402 * By convention, the name should begin with the name of the
403 * subsystem, followed by a period. Zero length string indicates
404 * end of cftype array.
406 char name
[MAX_CFTYPE_NAME
];
409 * If not 0, file mode is set to this value, otherwise it will
410 * be figured out automatically
415 * If non-zero, defines the maximum length of string that can
416 * be passed to write_string; defaults to 64
418 size_t max_write_len
;
424 struct simple_xattrs xattrs
;
426 int (*open
)(struct inode
*inode
, struct file
*file
);
427 ssize_t (*read
)(struct cgroup
*cgrp
, struct cftype
*cft
,
429 char __user
*buf
, size_t nbytes
, loff_t
*ppos
);
431 * read_u64() is a shortcut for the common case of returning a
432 * single integer. Use it in place of read()
434 u64 (*read_u64
)(struct cgroup
*cgrp
, struct cftype
*cft
);
436 * read_s64() is a signed version of read_u64()
438 s64 (*read_s64
)(struct cgroup
*cgrp
, struct cftype
*cft
);
440 * read_map() is used for defining a map of key/value
441 * pairs. It should call cb->fill(cb, key, value) for each
442 * entry. The key/value pairs (and their ordering) should not
443 * change between reboots.
445 int (*read_map
)(struct cgroup
*cont
, struct cftype
*cft
,
446 struct cgroup_map_cb
*cb
);
448 * read_seq_string() is used for outputting a simple sequence
451 int (*read_seq_string
)(struct cgroup
*cont
, struct cftype
*cft
,
454 ssize_t (*write
)(struct cgroup
*cgrp
, struct cftype
*cft
,
456 const char __user
*buf
, size_t nbytes
, loff_t
*ppos
);
459 * write_u64() is a shortcut for the common case of accepting
460 * a single integer (as parsed by simple_strtoull) from
461 * userspace. Use in place of write(); return 0 or error.
463 int (*write_u64
)(struct cgroup
*cgrp
, struct cftype
*cft
, u64 val
);
465 * write_s64() is a signed version of write_u64()
467 int (*write_s64
)(struct cgroup
*cgrp
, struct cftype
*cft
, s64 val
);
470 * write_string() is passed a nul-terminated kernelspace
471 * buffer of maximum length determined by max_write_len.
472 * Returns 0 or -ve error code.
474 int (*write_string
)(struct cgroup
*cgrp
, struct cftype
*cft
,
477 * trigger() callback can be used to get some kick from the
478 * userspace, when the actual string written is not important
479 * at all. The private field can be used to determine the
480 * kick type for multiplexing.
482 int (*trigger
)(struct cgroup
*cgrp
, unsigned int event
);
484 int (*release
)(struct inode
*inode
, struct file
*file
);
487 * register_event() callback will be used to add new userspace
488 * waiter for changes related to the cftype. Implement it if
489 * you want to provide this functionality. Use eventfd_signal()
490 * on eventfd to send notification to userspace.
492 int (*register_event
)(struct cgroup
*cgrp
, struct cftype
*cft
,
493 struct eventfd_ctx
*eventfd
, const char *args
);
495 * unregister_event() callback will be called when userspace
496 * closes the eventfd or on cgroup removing.
497 * This callback must be implemented, if you want provide
498 * notification functionality.
500 void (*unregister_event
)(struct cgroup
*cgrp
, struct cftype
*cft
,
501 struct eventfd_ctx
*eventfd
);
505 * cftype_sets describe cftypes belonging to a subsystem and are chained at
506 * cgroup_subsys->cftsets. Each cftset points to an array of cftypes
507 * terminated by zero length name.
510 struct list_head node
; /* chained at subsys->cftsets */
514 struct cgroup_scanner
{
516 int (*test_task
)(struct task_struct
*p
, struct cgroup_scanner
*scan
);
517 void (*process_task
)(struct task_struct
*p
,
518 struct cgroup_scanner
*scan
);
519 struct ptr_heap
*heap
;
524 * See the comment above CGRP_ROOT_SANE_BEHAVIOR for details. This
525 * function can be called as long as @cgrp is accessible.
527 static inline bool cgroup_sane_behavior(const struct cgroup
*cgrp
)
529 return cgrp
->root
->flags
& CGRP_ROOT_SANE_BEHAVIOR
;
532 /* Caller should hold rcu_read_lock() */
533 static inline const char *cgroup_name(const struct cgroup
*cgrp
)
535 return rcu_dereference(cgrp
->name
)->name
;
538 int cgroup_add_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
);
539 int cgroup_rm_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
);
541 int cgroup_is_removed(const struct cgroup
*cgrp
);
542 bool cgroup_is_descendant(struct cgroup
*cgrp
, struct cgroup
*ancestor
);
544 int cgroup_path(const struct cgroup
*cgrp
, char *buf
, int buflen
);
546 int cgroup_task_count(const struct cgroup
*cgrp
);
549 * Control Group taskset, used to pass around set of tasks to cgroup_subsys
552 struct cgroup_taskset
;
553 struct task_struct
*cgroup_taskset_first(struct cgroup_taskset
*tset
);
554 struct task_struct
*cgroup_taskset_next(struct cgroup_taskset
*tset
);
555 struct cgroup
*cgroup_taskset_cur_cgroup(struct cgroup_taskset
*tset
);
556 int cgroup_taskset_size(struct cgroup_taskset
*tset
);
559 * cgroup_taskset_for_each - iterate cgroup_taskset
560 * @task: the loop cursor
561 * @skip_cgrp: skip if task's cgroup matches this, %NULL to iterate through all
562 * @tset: taskset to iterate
564 #define cgroup_taskset_for_each(task, skip_cgrp, tset) \
565 for ((task) = cgroup_taskset_first((tset)); (task); \
566 (task) = cgroup_taskset_next((tset))) \
567 if (!(skip_cgrp) || \
568 cgroup_taskset_cur_cgroup((tset)) != (skip_cgrp))
571 * Control Group subsystem type.
572 * See Documentation/cgroups/cgroups.txt for details
575 struct cgroup_subsys
{
576 struct cgroup_subsys_state
*(*css_alloc
)(struct cgroup
*cgrp
);
577 int (*css_online
)(struct cgroup
*cgrp
);
578 void (*css_offline
)(struct cgroup
*cgrp
);
579 void (*css_free
)(struct cgroup
*cgrp
);
581 int (*can_attach
)(struct cgroup
*cgrp
, struct cgroup_taskset
*tset
);
582 void (*cancel_attach
)(struct cgroup
*cgrp
, struct cgroup_taskset
*tset
);
583 void (*attach
)(struct cgroup
*cgrp
, struct cgroup_taskset
*tset
);
584 void (*fork
)(struct task_struct
*task
);
585 void (*exit
)(struct cgroup
*cgrp
, struct cgroup
*old_cgrp
,
586 struct task_struct
*task
);
587 void (*bind
)(struct cgroup
*root
);
594 * True if this subsys uses ID. ID is not available before cgroup_init()
595 * (not available in early_init time.)
600 * If %false, this subsystem is properly hierarchical -
601 * configuration, resource accounting and restriction on a parent
602 * cgroup cover those of its children. If %true, hierarchy support
603 * is broken in some ways - some subsystems ignore hierarchy
604 * completely while others are only implemented half-way.
606 * It's now disallowed to create nested cgroups if the subsystem is
607 * broken and cgroup core will emit a warning message on such
608 * cases. Eventually, all subsystems will be made properly
609 * hierarchical and this will go away.
611 bool broken_hierarchy
;
612 bool warned_broken_hierarchy
;
614 #define MAX_CGROUP_TYPE_NAMELEN 32
618 * Link to parent, and list entry in parent's children.
619 * Protected by cgroup_lock()
621 struct cgroupfs_root
*root
;
622 struct list_head sibling
;
623 /* used when use_id == true */
627 /* list of cftype_sets */
628 struct list_head cftsets
;
630 /* base cftypes, automatically [de]registered with subsys itself */
631 struct cftype
*base_cftypes
;
632 struct cftype_set base_cftset
;
634 /* should be defined only by modular subsystems */
635 struct module
*module
;
638 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
639 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
640 #include <linux/cgroup_subsys.h>
641 #undef IS_SUBSYS_ENABLED
644 static inline struct cgroup_subsys_state
*cgroup_subsys_state(
645 struct cgroup
*cgrp
, int subsys_id
)
647 return cgrp
->subsys
[subsys_id
];
651 * function to get the cgroup_subsys_state which allows for extra
652 * rcu_dereference_check() conditions, such as locks used during the
653 * cgroup_subsys::attach() methods.
655 #ifdef CONFIG_PROVE_RCU
656 extern struct mutex cgroup_mutex
;
657 #define task_subsys_state_check(task, subsys_id, __c) \
658 rcu_dereference_check((task)->cgroups->subsys[(subsys_id)], \
659 lockdep_is_held(&(task)->alloc_lock) || \
660 lockdep_is_held(&cgroup_mutex) || (__c))
662 #define task_subsys_state_check(task, subsys_id, __c) \
663 rcu_dereference((task)->cgroups->subsys[(subsys_id)])
666 static inline struct cgroup_subsys_state
*
667 task_subsys_state(struct task_struct
*task
, int subsys_id
)
669 return task_subsys_state_check(task
, subsys_id
, false);
672 static inline struct cgroup
* task_cgroup(struct task_struct
*task
,
675 return task_subsys_state(task
, subsys_id
)->cgroup
;
679 * cgroup_for_each_child - iterate through children of a cgroup
680 * @pos: the cgroup * to use as the loop cursor
681 * @cgroup: cgroup whose children to walk
683 * Walk @cgroup's children. Must be called under rcu_read_lock(). A child
684 * cgroup which hasn't finished ->css_online() or already has finished
685 * ->css_offline() may show up during traversal and it's each subsystem's
686 * responsibility to verify that each @pos is alive.
688 * If a subsystem synchronizes against the parent in its ->css_online() and
689 * before starting iterating, a cgroup which finished ->css_online() is
690 * guaranteed to be visible in the future iterations.
692 #define cgroup_for_each_child(pos, cgroup) \
693 list_for_each_entry_rcu(pos, &(cgroup)->children, sibling)
695 struct cgroup
*cgroup_next_descendant_pre(struct cgroup
*pos
,
696 struct cgroup
*cgroup
);
697 struct cgroup
*cgroup_rightmost_descendant(struct cgroup
*pos
);
700 * cgroup_for_each_descendant_pre - pre-order walk of a cgroup's descendants
701 * @pos: the cgroup * to use as the loop cursor
702 * @cgroup: cgroup whose descendants to walk
704 * Walk @cgroup's descendants. Must be called under rcu_read_lock(). A
705 * descendant cgroup which hasn't finished ->css_online() or already has
706 * finished ->css_offline() may show up during traversal and it's each
707 * subsystem's responsibility to verify that each @pos is alive.
709 * If a subsystem synchronizes against the parent in its ->css_online() and
710 * before starting iterating, and synchronizes against @pos on each
711 * iteration, any descendant cgroup which finished ->css_offline() is
712 * guaranteed to be visible in the future iterations.
714 * In other words, the following guarantees that a descendant can't escape
715 * state updates of its ancestors.
719 * Lock @cgrp->parent and @cgrp;
720 * Inherit state from @cgrp->parent;
724 * my_update_state(@cgrp)
727 * Update @cgrp's state;
730 * cgroup_for_each_descendant_pre(@pos, @cgrp) {
732 * Verify @pos is alive and inherit state from @pos->parent;
737 * As long as the inheriting step, including checking the parent state, is
738 * enclosed inside @pos locking, double-locking the parent isn't necessary
739 * while inheriting. The state update to the parent is guaranteed to be
740 * visible by walking order and, as long as inheriting operations to the
741 * same @pos are atomic to each other, multiple updates racing each other
742 * still result in the correct state. It's guaranateed that at least one
743 * inheritance happens for any cgroup after the latest update to its
746 * If checking parent's state requires locking the parent, each inheriting
747 * iteration should lock and unlock both @pos->parent and @pos.
749 * Alternatively, a subsystem may choose to use a single global lock to
750 * synchronize ->css_online() and ->css_offline() against tree-walking
753 #define cgroup_for_each_descendant_pre(pos, cgroup) \
754 for (pos = cgroup_next_descendant_pre(NULL, (cgroup)); (pos); \
755 pos = cgroup_next_descendant_pre((pos), (cgroup)))
757 struct cgroup
*cgroup_next_descendant_post(struct cgroup
*pos
,
758 struct cgroup
*cgroup
);
761 * cgroup_for_each_descendant_post - post-order walk of a cgroup's descendants
762 * @pos: the cgroup * to use as the loop cursor
763 * @cgroup: cgroup whose descendants to walk
765 * Similar to cgroup_for_each_descendant_pre() but performs post-order
766 * traversal instead. Note that the walk visibility guarantee described in
767 * pre-order walk doesn't apply the same to post-order walks.
769 #define cgroup_for_each_descendant_post(pos, cgroup) \
770 for (pos = cgroup_next_descendant_post(NULL, (cgroup)); (pos); \
771 pos = cgroup_next_descendant_post((pos), (cgroup)))
773 /* A cgroup_iter should be treated as an opaque object */
775 struct list_head
*cg_link
;
776 struct list_head
*task
;
780 * To iterate across the tasks in a cgroup:
782 * 1) call cgroup_iter_start to initialize an iterator
784 * 2) call cgroup_iter_next() to retrieve member tasks until it
785 * returns NULL or until you want to end the iteration
787 * 3) call cgroup_iter_end() to destroy the iterator.
789 * Or, call cgroup_scan_tasks() to iterate through every task in a
790 * cgroup - cgroup_scan_tasks() holds the css_set_lock when calling
791 * the test_task() callback, but not while calling the process_task()
794 void cgroup_iter_start(struct cgroup
*cgrp
, struct cgroup_iter
*it
);
795 struct task_struct
*cgroup_iter_next(struct cgroup
*cgrp
,
796 struct cgroup_iter
*it
);
797 void cgroup_iter_end(struct cgroup
*cgrp
, struct cgroup_iter
*it
);
798 int cgroup_scan_tasks(struct cgroup_scanner
*scan
);
799 int cgroup_attach_task_all(struct task_struct
*from
, struct task_struct
*);
800 int cgroup_transfer_tasks(struct cgroup
*to
, struct cgroup
*from
);
803 * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
804 * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
805 * CSS ID is assigned at cgroup allocation (create) automatically
806 * and removed when subsys calls free_css_id() function. This is because
807 * the lifetime of cgroup_subsys_state is subsys's matter.
809 * Looking up and scanning function should be called under rcu_read_lock().
810 * Taking cgroup_mutex is not necessary for following calls.
811 * But the css returned by this routine can be "not populated yet" or "being
812 * destroyed". The caller should check css and cgroup's status.
816 * Typically Called at ->destroy(), or somewhere the subsys frees
817 * cgroup_subsys_state.
819 void free_css_id(struct cgroup_subsys
*ss
, struct cgroup_subsys_state
*css
);
821 /* Find a cgroup_subsys_state which has given ID */
823 struct cgroup_subsys_state
*css_lookup(struct cgroup_subsys
*ss
, int id
);
826 * Get a cgroup whose id is greater than or equal to id under tree of root.
827 * Returning a cgroup_subsys_state or NULL.
829 struct cgroup_subsys_state
*css_get_next(struct cgroup_subsys
*ss
, int id
,
830 struct cgroup_subsys_state
*root
, int *foundid
);
832 /* Returns true if root is ancestor of cg */
833 bool css_is_ancestor(struct cgroup_subsys_state
*cg
,
834 const struct cgroup_subsys_state
*root
);
836 /* Get id and depth of css */
837 unsigned short css_id(struct cgroup_subsys_state
*css
);
838 unsigned short css_depth(struct cgroup_subsys_state
*css
);
839 struct cgroup_subsys_state
*cgroup_css_from_dir(struct file
*f
, int id
);
841 #else /* !CONFIG_CGROUPS */
843 static inline int cgroup_init_early(void) { return 0; }
844 static inline int cgroup_init(void) { return 0; }
845 static inline void cgroup_fork(struct task_struct
*p
) {}
846 static inline void cgroup_post_fork(struct task_struct
*p
) {}
847 static inline void cgroup_exit(struct task_struct
*p
, int callbacks
) {}
849 static inline void cgroup_lock(void) {}
850 static inline void cgroup_unlock(void) {}
851 static inline int cgroupstats_build(struct cgroupstats
*stats
,
852 struct dentry
*dentry
)
857 /* No cgroups - nothing to do */
858 static inline int cgroup_attach_task_all(struct task_struct
*from
,
859 struct task_struct
*t
)
864 #endif /* !CONFIG_CGROUPS */
866 #endif /* _LINUX_CGROUP_H */