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 * - memcg: use_hierarchy is on by default and the cgroup file for
281 * the flag is not created.
283 * The followings are planned changes.
285 * - release_agent will be disallowed once replacement notification
286 * mechanism is implemented.
288 CGRP_ROOT_SANE_BEHAVIOR
= (1 << 0),
290 CGRP_ROOT_NOPREFIX
= (1 << 1), /* mounted subsystems have no named prefix */
291 CGRP_ROOT_XATTR
= (1 << 2), /* supports extended attributes */
295 * A cgroupfs_root represents the root of a cgroup hierarchy, and may be
296 * associated with a superblock to form an active hierarchy. This is
297 * internal to cgroup core. Don't access directly from controllers.
299 struct cgroupfs_root
{
300 struct super_block
*sb
;
303 * The bitmask of subsystems intended to be attached to this
306 unsigned long subsys_mask
;
308 /* Unique id for this hierarchy. */
311 /* The bitmask of subsystems currently attached to this hierarchy */
312 unsigned long actual_subsys_mask
;
314 /* A list running through the attached subsystems */
315 struct list_head subsys_list
;
317 /* The root cgroup for this hierarchy */
318 struct cgroup top_cgroup
;
320 /* Tracks how many cgroups are currently defined in hierarchy.*/
321 int number_of_cgroups
;
323 /* A list running through the active hierarchies */
324 struct list_head root_list
;
326 /* All cgroups on this root, cgroup_mutex protected */
327 struct list_head allcg_list
;
329 /* Hierarchy-specific flags */
332 /* IDs for cgroups in this hierarchy */
333 struct ida cgroup_ida
;
335 /* The path to use for release notifications. */
336 char release_agent_path
[PATH_MAX
];
338 /* The name for this hierarchy - may be empty */
339 char name
[MAX_CGROUP_ROOT_NAMELEN
];
343 * A css_set is a structure holding pointers to a set of
344 * cgroup_subsys_state objects. This saves space in the task struct
345 * object and speeds up fork()/exit(), since a single inc/dec and a
346 * list_add()/del() can bump the reference count on the entire cgroup
352 /* Reference count */
356 * List running through all cgroup groups in the same hash
357 * slot. Protected by css_set_lock
359 struct hlist_node hlist
;
362 * List running through all tasks using this cgroup
363 * group. Protected by css_set_lock
365 struct list_head tasks
;
368 * List of cg_cgroup_link objects on link chains from
369 * cgroups referenced from this css_set. Protected by
372 struct list_head cg_links
;
375 * Set of subsystem states, one for each subsystem. This array
376 * is immutable after creation apart from the init_css_set
377 * during subsystem registration (at boot time) and modular subsystem
380 struct cgroup_subsys_state
*subsys
[CGROUP_SUBSYS_COUNT
];
382 /* For RCU-protected deletion */
383 struct rcu_head rcu_head
;
387 * cgroup_map_cb is an abstract callback API for reporting map-valued
391 struct cgroup_map_cb
{
392 int (*fill
)(struct cgroup_map_cb
*cb
, const char *key
, u64 value
);
397 * struct cftype: handler definitions for cgroup control files
399 * When reading/writing to a file:
400 * - the cgroup to use is file->f_dentry->d_parent->d_fsdata
401 * - the 'cftype' of the file is file->f_dentry->d_fsdata
405 #define CFTYPE_ONLY_ON_ROOT (1U << 0) /* only create on root cg */
406 #define CFTYPE_NOT_ON_ROOT (1U << 1) /* don't create on root cg */
407 #define CFTYPE_INSANE (1U << 2) /* don't create if sane_behavior */
409 #define MAX_CFTYPE_NAME 64
413 * By convention, the name should begin with the name of the
414 * subsystem, followed by a period. Zero length string indicates
415 * end of cftype array.
417 char name
[MAX_CFTYPE_NAME
];
420 * If not 0, file mode is set to this value, otherwise it will
421 * be figured out automatically
426 * If non-zero, defines the maximum length of string that can
427 * be passed to write_string; defaults to 64
429 size_t max_write_len
;
434 int (*open
)(struct inode
*inode
, struct file
*file
);
435 ssize_t (*read
)(struct cgroup
*cgrp
, struct cftype
*cft
,
437 char __user
*buf
, size_t nbytes
, loff_t
*ppos
);
439 * read_u64() is a shortcut for the common case of returning a
440 * single integer. Use it in place of read()
442 u64 (*read_u64
)(struct cgroup
*cgrp
, struct cftype
*cft
);
444 * read_s64() is a signed version of read_u64()
446 s64 (*read_s64
)(struct cgroup
*cgrp
, struct cftype
*cft
);
448 * read_map() is used for defining a map of key/value
449 * pairs. It should call cb->fill(cb, key, value) for each
450 * entry. The key/value pairs (and their ordering) should not
451 * change between reboots.
453 int (*read_map
)(struct cgroup
*cont
, struct cftype
*cft
,
454 struct cgroup_map_cb
*cb
);
456 * read_seq_string() is used for outputting a simple sequence
459 int (*read_seq_string
)(struct cgroup
*cont
, struct cftype
*cft
,
462 ssize_t (*write
)(struct cgroup
*cgrp
, struct cftype
*cft
,
464 const char __user
*buf
, size_t nbytes
, loff_t
*ppos
);
467 * write_u64() is a shortcut for the common case of accepting
468 * a single integer (as parsed by simple_strtoull) from
469 * userspace. Use in place of write(); return 0 or error.
471 int (*write_u64
)(struct cgroup
*cgrp
, struct cftype
*cft
, u64 val
);
473 * write_s64() is a signed version of write_u64()
475 int (*write_s64
)(struct cgroup
*cgrp
, struct cftype
*cft
, s64 val
);
478 * write_string() is passed a nul-terminated kernelspace
479 * buffer of maximum length determined by max_write_len.
480 * Returns 0 or -ve error code.
482 int (*write_string
)(struct cgroup
*cgrp
, struct cftype
*cft
,
485 * trigger() callback can be used to get some kick from the
486 * userspace, when the actual string written is not important
487 * at all. The private field can be used to determine the
488 * kick type for multiplexing.
490 int (*trigger
)(struct cgroup
*cgrp
, unsigned int event
);
492 int (*release
)(struct inode
*inode
, struct file
*file
);
495 * register_event() callback will be used to add new userspace
496 * waiter for changes related to the cftype. Implement it if
497 * you want to provide this functionality. Use eventfd_signal()
498 * on eventfd to send notification to userspace.
500 int (*register_event
)(struct cgroup
*cgrp
, struct cftype
*cft
,
501 struct eventfd_ctx
*eventfd
, const char *args
);
503 * unregister_event() callback will be called when userspace
504 * closes the eventfd or on cgroup removing.
505 * This callback must be implemented, if you want provide
506 * notification functionality.
508 void (*unregister_event
)(struct cgroup
*cgrp
, struct cftype
*cft
,
509 struct eventfd_ctx
*eventfd
);
513 * cftype_sets describe cftypes belonging to a subsystem and are chained at
514 * cgroup_subsys->cftsets. Each cftset points to an array of cftypes
515 * terminated by zero length name.
518 struct list_head node
; /* chained at subsys->cftsets */
522 struct cgroup_scanner
{
524 int (*test_task
)(struct task_struct
*p
, struct cgroup_scanner
*scan
);
525 void (*process_task
)(struct task_struct
*p
,
526 struct cgroup_scanner
*scan
);
527 struct ptr_heap
*heap
;
532 * See the comment above CGRP_ROOT_SANE_BEHAVIOR for details. This
533 * function can be called as long as @cgrp is accessible.
535 static inline bool cgroup_sane_behavior(const struct cgroup
*cgrp
)
537 return cgrp
->root
->flags
& CGRP_ROOT_SANE_BEHAVIOR
;
540 /* Caller should hold rcu_read_lock() */
541 static inline const char *cgroup_name(const struct cgroup
*cgrp
)
543 return rcu_dereference(cgrp
->name
)->name
;
546 int cgroup_add_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
);
547 int cgroup_rm_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
);
549 bool cgroup_is_descendant(struct cgroup
*cgrp
, struct cgroup
*ancestor
);
551 int cgroup_path(const struct cgroup
*cgrp
, char *buf
, int buflen
);
552 int task_cgroup_path_from_hierarchy(struct task_struct
*task
, int hierarchy_id
,
553 char *buf
, size_t buflen
);
555 int cgroup_task_count(const struct cgroup
*cgrp
);
558 * Control Group taskset, used to pass around set of tasks to cgroup_subsys
561 struct cgroup_taskset
;
562 struct task_struct
*cgroup_taskset_first(struct cgroup_taskset
*tset
);
563 struct task_struct
*cgroup_taskset_next(struct cgroup_taskset
*tset
);
564 struct cgroup
*cgroup_taskset_cur_cgroup(struct cgroup_taskset
*tset
);
565 int cgroup_taskset_size(struct cgroup_taskset
*tset
);
568 * cgroup_taskset_for_each - iterate cgroup_taskset
569 * @task: the loop cursor
570 * @skip_cgrp: skip if task's cgroup matches this, %NULL to iterate through all
571 * @tset: taskset to iterate
573 #define cgroup_taskset_for_each(task, skip_cgrp, tset) \
574 for ((task) = cgroup_taskset_first((tset)); (task); \
575 (task) = cgroup_taskset_next((tset))) \
576 if (!(skip_cgrp) || \
577 cgroup_taskset_cur_cgroup((tset)) != (skip_cgrp))
580 * Control Group subsystem type.
581 * See Documentation/cgroups/cgroups.txt for details
584 struct cgroup_subsys
{
585 struct cgroup_subsys_state
*(*css_alloc
)(struct cgroup
*cgrp
);
586 int (*css_online
)(struct cgroup
*cgrp
);
587 void (*css_offline
)(struct cgroup
*cgrp
);
588 void (*css_free
)(struct cgroup
*cgrp
);
590 int (*can_attach
)(struct cgroup
*cgrp
, struct cgroup_taskset
*tset
);
591 void (*cancel_attach
)(struct cgroup
*cgrp
, struct cgroup_taskset
*tset
);
592 void (*attach
)(struct cgroup
*cgrp
, struct cgroup_taskset
*tset
);
593 void (*fork
)(struct task_struct
*task
);
594 void (*exit
)(struct cgroup
*cgrp
, struct cgroup
*old_cgrp
,
595 struct task_struct
*task
);
596 void (*bind
)(struct cgroup
*root
);
602 * True if this subsys uses ID. ID is not available before cgroup_init()
603 * (not available in early_init time.)
608 * If %false, this subsystem is properly hierarchical -
609 * configuration, resource accounting and restriction on a parent
610 * cgroup cover those of its children. If %true, hierarchy support
611 * is broken in some ways - some subsystems ignore hierarchy
612 * completely while others are only implemented half-way.
614 * It's now disallowed to create nested cgroups if the subsystem is
615 * broken and cgroup core will emit a warning message on such
616 * cases. Eventually, all subsystems will be made properly
617 * hierarchical and this will go away.
619 bool broken_hierarchy
;
620 bool warned_broken_hierarchy
;
622 #define MAX_CGROUP_TYPE_NAMELEN 32
626 * Link to parent, and list entry in parent's children.
627 * Protected by cgroup_lock()
629 struct cgroupfs_root
*root
;
630 struct list_head sibling
;
631 /* used when use_id == true */
635 /* list of cftype_sets */
636 struct list_head cftsets
;
638 /* base cftypes, automatically [de]registered with subsys itself */
639 struct cftype
*base_cftypes
;
640 struct cftype_set base_cftset
;
642 /* should be defined only by modular subsystems */
643 struct module
*module
;
646 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
647 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
648 #include <linux/cgroup_subsys.h>
649 #undef IS_SUBSYS_ENABLED
652 static inline struct cgroup_subsys_state
*cgroup_subsys_state(
653 struct cgroup
*cgrp
, int subsys_id
)
655 return cgrp
->subsys
[subsys_id
];
659 * function to get the cgroup_subsys_state which allows for extra
660 * rcu_dereference_check() conditions, such as locks used during the
661 * cgroup_subsys::attach() methods.
663 #ifdef CONFIG_PROVE_RCU
664 extern struct mutex cgroup_mutex
;
665 #define task_subsys_state_check(task, subsys_id, __c) \
666 rcu_dereference_check((task)->cgroups->subsys[(subsys_id)], \
667 lockdep_is_held(&(task)->alloc_lock) || \
668 lockdep_is_held(&cgroup_mutex) || (__c))
670 #define task_subsys_state_check(task, subsys_id, __c) \
671 rcu_dereference((task)->cgroups->subsys[(subsys_id)])
674 static inline struct cgroup_subsys_state
*
675 task_subsys_state(struct task_struct
*task
, int subsys_id
)
677 return task_subsys_state_check(task
, subsys_id
, false);
680 static inline struct cgroup
* task_cgroup(struct task_struct
*task
,
683 return task_subsys_state(task
, subsys_id
)->cgroup
;
686 struct cgroup
*cgroup_next_sibling(struct cgroup
*pos
);
689 * cgroup_for_each_child - iterate through children of a cgroup
690 * @pos: the cgroup * to use as the loop cursor
691 * @cgrp: cgroup whose children to walk
693 * Walk @cgrp's children. Must be called under rcu_read_lock(). A child
694 * cgroup which hasn't finished ->css_online() or already has finished
695 * ->css_offline() may show up during traversal and it's each subsystem's
696 * responsibility to verify that each @pos is alive.
698 * If a subsystem synchronizes against the parent in its ->css_online() and
699 * before starting iterating, a cgroup which finished ->css_online() is
700 * guaranteed to be visible in the future iterations.
702 * It is allowed to temporarily drop RCU read lock during iteration. The
703 * caller is responsible for ensuring that @pos remains accessible until
704 * the start of the next iteration by, for example, bumping the css refcnt.
706 #define cgroup_for_each_child(pos, cgrp) \
707 for ((pos) = list_first_or_null_rcu(&(cgrp)->children, \
708 struct cgroup, sibling); \
709 (pos); (pos) = cgroup_next_sibling((pos)))
711 struct cgroup
*cgroup_next_descendant_pre(struct cgroup
*pos
,
712 struct cgroup
*cgroup
);
713 struct cgroup
*cgroup_rightmost_descendant(struct cgroup
*pos
);
716 * cgroup_for_each_descendant_pre - pre-order walk of a cgroup's descendants
717 * @pos: the cgroup * to use as the loop cursor
718 * @cgroup: cgroup whose descendants to walk
720 * Walk @cgroup's descendants. Must be called under rcu_read_lock(). A
721 * descendant cgroup which hasn't finished ->css_online() or already has
722 * finished ->css_offline() may show up during traversal and it's each
723 * subsystem's responsibility to verify that each @pos is alive.
725 * If a subsystem synchronizes against the parent in its ->css_online() and
726 * before starting iterating, and synchronizes against @pos on each
727 * iteration, any descendant cgroup which finished ->css_online() is
728 * guaranteed to be visible in the future iterations.
730 * In other words, the following guarantees that a descendant can't escape
731 * state updates of its ancestors.
735 * Lock @cgrp->parent and @cgrp;
736 * Inherit state from @cgrp->parent;
740 * my_update_state(@cgrp)
743 * Update @cgrp's state;
746 * cgroup_for_each_descendant_pre(@pos, @cgrp) {
748 * Verify @pos is alive and inherit state from @pos->parent;
753 * As long as the inheriting step, including checking the parent state, is
754 * enclosed inside @pos locking, double-locking the parent isn't necessary
755 * while inheriting. The state update to the parent is guaranteed to be
756 * visible by walking order and, as long as inheriting operations to the
757 * same @pos are atomic to each other, multiple updates racing each other
758 * still result in the correct state. It's guaranateed that at least one
759 * inheritance happens for any cgroup after the latest update to its
762 * If checking parent's state requires locking the parent, each inheriting
763 * iteration should lock and unlock both @pos->parent and @pos.
765 * Alternatively, a subsystem may choose to use a single global lock to
766 * synchronize ->css_online() and ->css_offline() against tree-walking
769 * It is allowed to temporarily drop RCU read lock during iteration. The
770 * caller is responsible for ensuring that @pos remains accessible until
771 * the start of the next iteration by, for example, bumping the css refcnt.
773 #define cgroup_for_each_descendant_pre(pos, cgroup) \
774 for (pos = cgroup_next_descendant_pre(NULL, (cgroup)); (pos); \
775 pos = cgroup_next_descendant_pre((pos), (cgroup)))
777 struct cgroup
*cgroup_next_descendant_post(struct cgroup
*pos
,
778 struct cgroup
*cgroup
);
781 * cgroup_for_each_descendant_post - post-order walk of a cgroup's descendants
782 * @pos: the cgroup * to use as the loop cursor
783 * @cgroup: cgroup whose descendants to walk
785 * Similar to cgroup_for_each_descendant_pre() but performs post-order
786 * traversal instead. Note that the walk visibility guarantee described in
787 * pre-order walk doesn't apply the same to post-order walks.
789 #define cgroup_for_each_descendant_post(pos, cgroup) \
790 for (pos = cgroup_next_descendant_post(NULL, (cgroup)); (pos); \
791 pos = cgroup_next_descendant_post((pos), (cgroup)))
793 /* A cgroup_iter should be treated as an opaque object */
795 struct list_head
*cg_link
;
796 struct list_head
*task
;
800 * To iterate across the tasks in a cgroup:
802 * 1) call cgroup_iter_start to initialize an iterator
804 * 2) call cgroup_iter_next() to retrieve member tasks until it
805 * returns NULL or until you want to end the iteration
807 * 3) call cgroup_iter_end() to destroy the iterator.
809 * Or, call cgroup_scan_tasks() to iterate through every task in a
810 * cgroup - cgroup_scan_tasks() holds the css_set_lock when calling
811 * the test_task() callback, but not while calling the process_task()
814 void cgroup_iter_start(struct cgroup
*cgrp
, struct cgroup_iter
*it
);
815 struct task_struct
*cgroup_iter_next(struct cgroup
*cgrp
,
816 struct cgroup_iter
*it
);
817 void cgroup_iter_end(struct cgroup
*cgrp
, struct cgroup_iter
*it
);
818 int cgroup_scan_tasks(struct cgroup_scanner
*scan
);
819 int cgroup_attach_task_all(struct task_struct
*from
, struct task_struct
*);
820 int cgroup_transfer_tasks(struct cgroup
*to
, struct cgroup
*from
);
823 * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
824 * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
825 * CSS ID is assigned at cgroup allocation (create) automatically
826 * and removed when subsys calls free_css_id() function. This is because
827 * the lifetime of cgroup_subsys_state is subsys's matter.
829 * Looking up and scanning function should be called under rcu_read_lock().
830 * Taking cgroup_mutex is not necessary for following calls.
831 * But the css returned by this routine can be "not populated yet" or "being
832 * destroyed". The caller should check css and cgroup's status.
836 * Typically Called at ->destroy(), or somewhere the subsys frees
837 * cgroup_subsys_state.
839 void free_css_id(struct cgroup_subsys
*ss
, struct cgroup_subsys_state
*css
);
841 /* Find a cgroup_subsys_state which has given ID */
843 struct cgroup_subsys_state
*css_lookup(struct cgroup_subsys
*ss
, int id
);
845 /* Returns true if root is ancestor of cg */
846 bool css_is_ancestor(struct cgroup_subsys_state
*cg
,
847 const struct cgroup_subsys_state
*root
);
849 /* Get id and depth of css */
850 unsigned short css_id(struct cgroup_subsys_state
*css
);
851 struct cgroup_subsys_state
*cgroup_css_from_dir(struct file
*f
, int id
);
853 #else /* !CONFIG_CGROUPS */
855 static inline int cgroup_init_early(void) { return 0; }
856 static inline int cgroup_init(void) { return 0; }
857 static inline void cgroup_fork(struct task_struct
*p
) {}
858 static inline void cgroup_post_fork(struct task_struct
*p
) {}
859 static inline void cgroup_exit(struct task_struct
*p
, int callbacks
) {}
861 static inline int cgroupstats_build(struct cgroupstats
*stats
,
862 struct dentry
*dentry
)
867 /* No cgroups - nothing to do */
868 static inline int cgroup_attach_task_all(struct task_struct
*from
,
869 struct task_struct
*t
)
874 #endif /* !CONFIG_CGROUPS */
876 #endif /* _LINUX_CGROUP_H */