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>
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 {
68 /* the cgroup that this css is attached to */
69 struct cgroup *cgroup;
71 /* the cgroup subsystem that this css is attached to */
72 struct cgroup_subsys *ss;
74 /* reference count - access via css_[try]get() and css_put() */
75 struct percpu_ref refcnt;
78 struct cgroup_subsys_state *parent;
81 /* ID for this css, if possible */
82 struct css_id __rcu *id;
84 /* percpu_ref killing and RCU release */
85 struct rcu_head rcu_head;
86 struct work_struct destroy_work;
89 /* bits in struct cgroup_subsys_state flags field */
91 CSS_ROOT = (1 << 0), /* this CSS is the root of the subsystem */
92 CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */
96 * css_get - obtain a reference on the specified css
99 * The caller must already have a reference.
101 static inline void css_get(struct cgroup_subsys_state *css)
103 /* We don't need to reference count the root state */
104 if (!(css->flags & CSS_ROOT))
105 percpu_ref_get(&css->refcnt);
109 * css_tryget - try to obtain a reference on the specified css
112 * Obtain a reference on @css if it's alive. The caller naturally needs to
113 * ensure that @css is accessible but doesn't have to be holding a
114 * reference on it - IOW, RCU protected access is good enough for this
115 * function. Returns %true if a reference count was successfully obtained;
118 static inline bool css_tryget(struct cgroup_subsys_state *css)
120 if (css->flags & CSS_ROOT)
122 return percpu_ref_tryget(&css->refcnt);
126 * css_put - put a css reference
129 * Put a reference obtained via css_get() and css_tryget().
131 static inline void css_put(struct cgroup_subsys_state *css)
133 if (!(css->flags & CSS_ROOT))
134 percpu_ref_put(&css->refcnt);
137 /* bits in struct cgroup flags field */
139 /* Control Group is dead */
142 * Control Group has previously had a child cgroup or a task,
143 * but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
146 /* Control Group requires release notifications to userspace */
147 CGRP_NOTIFY_ON_RELEASE,
149 * Clone the parent's configuration when creating a new child
150 * cpuset cgroup. For historical reasons, this option can be
151 * specified at mount time and thus is implemented here.
153 CGRP_CPUSET_CLONE_CHILDREN,
154 /* see the comment above CGRP_ROOT_SANE_BEHAVIOR for details */
159 struct rcu_head rcu_head;
164 unsigned long flags; /* "unsigned long" so bitops work */
167 * idr allocated in-hierarchy ID.
169 * The ID of the root cgroup is always 0, and a new cgroup
170 * will be assigned with a smallest available ID.
174 /* the number of attached css's */
178 * We link our 'sibling' struct into our parent's 'children'.
179 * Our children link their 'sibling' into our 'children'.
181 struct list_head sibling; /* my parent's children */
182 struct list_head children; /* my children */
183 struct list_head files; /* my files */
185 struct cgroup *parent; /* my parent */
186 struct dentry *dentry; /* cgroup fs entry, RCU protected */
189 * Monotonically increasing unique serial number which defines a
190 * uniform order among all cgroups. It's guaranteed that all
191 * ->children lists are in the ascending order of ->serial_nr.
192 * It's used to allow interrupting and resuming iterations.
197 * This is a copy of dentry->d_name, and it's needed because
198 * we can't use dentry->d_name in cgroup_path().
200 * You must acquire rcu_read_lock() to access cgrp->name, and
201 * the only place that can change it is rename(), which is
202 * protected by parent dir's i_mutex.
204 * Normally you should use cgroup_name() wrapper rather than
205 * access it directly.
207 struct cgroup_name __rcu *name;
209 /* Private pointers for each registered subsystem */
210 struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
212 struct cgroupfs_root *root;
215 * List of cgrp_cset_links pointing at css_sets with tasks in this
216 * cgroup. Protected by css_set_lock.
218 struct list_head cset_links;
221 * Linked list running through all cgroups that can
222 * potentially be reaped by the release agent. Protected by
225 struct list_head release_list;
228 * list of pidlists, up to two for each namespace (one for procs, one
229 * for tasks); created on demand.
231 struct list_head pidlists;
232 struct mutex pidlist_mutex;
234 /* dummy css with NULL ->ss, points back to this cgroup */
235 struct cgroup_subsys_state dummy_css;
237 /* For css percpu_ref killing and RCU-protected deletion */
238 struct rcu_head rcu_head;
239 struct work_struct destroy_work;
241 /* directory xattrs */
242 struct simple_xattrs xattrs;
245 #define MAX_CGROUP_ROOT_NAMELEN 64
247 /* cgroupfs_root->flags */
250 * Unfortunately, cgroup core and various controllers are riddled
251 * with idiosyncrasies and pointless options. The following flag,
252 * when set, will force sane behavior - some options are forced on,
253 * others are disallowed, and some controllers will change their
254 * hierarchical or other behaviors.
256 * The set of behaviors affected by this flag are still being
257 * determined and developed and the mount option for this flag is
258 * prefixed with __DEVEL__. The prefix will be dropped once we
259 * reach the point where all behaviors are compatible with the
260 * planned unified hierarchy, which will automatically turn on this
263 * The followings are the behaviors currently affected this flag.
265 * - Mount options "noprefix" and "clone_children" are disallowed.
266 * Also, cgroupfs file cgroup.clone_children is not created.
268 * - When mounting an existing superblock, mount options should
271 * - Remount is disallowed.
273 * - rename(2) is disallowed.
275 * - "tasks" is removed. Everything should be at process
276 * granularity. Use "cgroup.procs" instead.
278 * - "release_agent" and "notify_on_release" are removed.
279 * Replacement notification mechanism will be implemented.
281 * - cpuset: tasks will be kept in empty cpusets when hotplug happens
282 * and take masks of ancestors with non-empty cpus/mems, instead of
283 * being moved to an ancestor.
285 * - cpuset: a task can be moved into an empty cpuset, and again it
286 * takes masks of ancestors.
288 * - memcg: use_hierarchy is on by default and the cgroup file for
289 * the flag is not created.
291 * - blkcg: blk-throttle becomes properly hierarchical.
293 CGRP_ROOT_SANE_BEHAVIOR = (1 << 0),
295 CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
296 CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
298 /* mount options live below bit 16 */
299 CGRP_ROOT_OPTION_MASK = (1 << 16) - 1,
301 CGRP_ROOT_SUBSYS_BOUND = (1 << 16), /* subsystems finished binding */
305 * A cgroupfs_root represents the root of a cgroup hierarchy, and may be
306 * associated with a superblock to form an active hierarchy. This is
307 * internal to cgroup core. Don't access directly from controllers.
309 struct cgroupfs_root {
310 struct super_block *sb;
312 /* The bitmask of subsystems attached to this hierarchy */
313 unsigned long subsys_mask;
315 /* Unique id for this hierarchy. */
318 /* A list running through the attached subsystems */
319 struct list_head subsys_list;
321 /* The root cgroup for this hierarchy */
322 struct cgroup top_cgroup;
324 /* Tracks how many cgroups are currently defined in hierarchy.*/
325 int number_of_cgroups;
327 /* A list running through the active hierarchies */
328 struct list_head root_list;
330 /* Hierarchy-specific flags */
333 /* IDs for cgroups in this hierarchy */
334 struct idr cgroup_idr;
336 /* The path to use for release notifications. */
337 char release_agent_path[PATH_MAX];
339 /* The name for this hierarchy - may be empty */
340 char name[MAX_CGROUP_ROOT_NAMELEN];
344 * A css_set is a structure holding pointers to a set of
345 * cgroup_subsys_state objects. This saves space in the task struct
346 * object and speeds up fork()/exit(), since a single inc/dec and a
347 * list_add()/del() can bump the reference count on the entire cgroup
353 /* Reference count */
357 * List running through all cgroup groups in the same hash
358 * slot. Protected by css_set_lock
360 struct hlist_node hlist;
363 * List running through all tasks using this cgroup
364 * group. Protected by css_set_lock
366 struct list_head tasks;
369 * List of cgrp_cset_links pointing at cgroups referenced from this
370 * css_set. Protected by css_set_lock.
372 struct list_head cgrp_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
406 CFTYPE_ONLY_ON_ROOT = (1 << 0), /* only create on root cgrp */
407 CFTYPE_NOT_ON_ROOT = (1 << 1), /* don't create on root cgrp */
408 CFTYPE_INSANE = (1 << 2), /* don't create if sane_behavior */
409 CFTYPE_NO_PREFIX = (1 << 3), /* (DON'T USE FOR NEW FILES) no subsys prefix */
412 #define MAX_CFTYPE_NAME 64
416 * By convention, the name should begin with the name of the
417 * subsystem, followed by a period. Zero length string indicates
418 * end of cftype array.
420 char name[MAX_CFTYPE_NAME];
423 * If not 0, file mode is set to this value, otherwise it will
424 * be figured out automatically
429 * If non-zero, defines the maximum length of string that can
430 * be passed to write_string; defaults to 64
432 size_t max_write_len;
438 * The subsys this file belongs to. Initialized automatically
439 * during registration. NULL for cgroup core files.
441 struct cgroup_subsys *ss;
443 int (*open)(struct inode *inode, struct file *file);
444 ssize_t (*read)(struct cgroup_subsys_state *css, struct cftype *cft,
446 char __user *buf, size_t nbytes, loff_t *ppos);
448 * read_u64() is a shortcut for the common case of returning a
449 * single integer. Use it in place of read()
451 u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft);
453 * read_s64() is a signed version of read_u64()
455 s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft);
457 * read_map() is used for defining a map of key/value
458 * pairs. It should call cb->fill(cb, key, value) for each
459 * entry. The key/value pairs (and their ordering) should not
460 * change between reboots.
462 int (*read_map)(struct cgroup_subsys_state *css, struct cftype *cft,
463 struct cgroup_map_cb *cb);
465 * read_seq_string() is used for outputting a simple sequence
468 int (*read_seq_string)(struct cgroup_subsys_state *css,
469 struct cftype *cft, struct seq_file *m);
471 ssize_t (*write)(struct cgroup_subsys_state *css, struct cftype *cft,
473 const char __user *buf, size_t nbytes, loff_t *ppos);
476 * write_u64() is a shortcut for the common case of accepting
477 * a single integer (as parsed by simple_strtoull) from
478 * userspace. Use in place of write(); return 0 or error.
480 int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft,
483 * write_s64() is a signed version of write_u64()
485 int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft,
489 * write_string() is passed a nul-terminated kernelspace
490 * buffer of maximum length determined by max_write_len.
491 * Returns 0 or -ve error code.
493 int (*write_string)(struct cgroup_subsys_state *css, struct cftype *cft,
496 * trigger() callback can be used to get some kick from the
497 * userspace, when the actual string written is not important
498 * at all. The private field can be used to determine the
499 * kick type for multiplexing.
501 int (*trigger)(struct cgroup_subsys_state *css, unsigned int event);
503 int (*release)(struct inode *inode, struct file *file);
507 * cftype_sets describe cftypes belonging to a subsystem and are chained at
508 * cgroup_subsys->cftsets. Each cftset points to an array of cftypes
509 * terminated by zero length name.
512 struct list_head node; /* chained at subsys->cftsets */
517 * See the comment above CGRP_ROOT_SANE_BEHAVIOR for details. This
518 * function can be called as long as @cgrp is accessible.
520 static inline bool cgroup_sane_behavior(const struct cgroup *cgrp)
522 return cgrp->root->flags & CGRP_ROOT_SANE_BEHAVIOR;
525 /* Caller should hold rcu_read_lock() */
526 static inline const char *cgroup_name(const struct cgroup *cgrp)
528 return rcu_dereference(cgrp->name)->name;
531 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
532 int cgroup_rm_cftypes(struct cftype *cfts);
534 bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
536 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
537 int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
539 int cgroup_task_count(const struct cgroup *cgrp);
542 * Control Group taskset, used to pass around set of tasks to cgroup_subsys
545 struct cgroup_taskset;
546 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
547 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
548 struct cgroup_subsys_state *cgroup_taskset_cur_css(struct cgroup_taskset *tset,
550 int cgroup_taskset_size(struct cgroup_taskset *tset);
553 * cgroup_taskset_for_each - iterate cgroup_taskset
554 * @task: the loop cursor
555 * @skip_css: skip if task's css matches this, %NULL to iterate through all
556 * @tset: taskset to iterate
558 #define cgroup_taskset_for_each(task, skip_css, tset) \
559 for ((task) = cgroup_taskset_first((tset)); (task); \
560 (task) = cgroup_taskset_next((tset))) \
562 cgroup_taskset_cur_css((tset), \
563 (skip_css)->ss->subsys_id) != (skip_css))
566 * Control Group subsystem type.
567 * See Documentation/cgroups/cgroups.txt for details
570 struct cgroup_subsys {
571 struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);
572 int (*css_online)(struct cgroup_subsys_state *css);
573 void (*css_offline)(struct cgroup_subsys_state *css);
574 void (*css_free)(struct cgroup_subsys_state *css);
576 int (*can_attach)(struct cgroup_subsys_state *css,
577 struct cgroup_taskset *tset);
578 void (*cancel_attach)(struct cgroup_subsys_state *css,
579 struct cgroup_taskset *tset);
580 void (*attach)(struct cgroup_subsys_state *css,
581 struct cgroup_taskset *tset);
582 void (*fork)(struct task_struct *task);
583 void (*exit)(struct cgroup_subsys_state *css,
584 struct cgroup_subsys_state *old_css,
585 struct task_struct *task);
586 void (*bind)(struct cgroup_subsys_state *root_css);
593 * If %false, this subsystem is properly hierarchical -
594 * configuration, resource accounting and restriction on a parent
595 * cgroup cover those of its children. If %true, hierarchy support
596 * is broken in some ways - some subsystems ignore hierarchy
597 * completely while others are only implemented half-way.
599 * It's now disallowed to create nested cgroups if the subsystem is
600 * broken and cgroup core will emit a warning message on such
601 * cases. Eventually, all subsystems will be made properly
602 * hierarchical and this will go away.
604 bool broken_hierarchy;
605 bool warned_broken_hierarchy;
607 #define MAX_CGROUP_TYPE_NAMELEN 32
611 * Link to parent, and list entry in parent's children.
612 * Protected by cgroup_lock()
614 struct cgroupfs_root *root;
615 struct list_head sibling;
617 /* list of cftype_sets */
618 struct list_head cftsets;
620 /* base cftypes, automatically [de]registered with subsys itself */
621 struct cftype *base_cftypes;
622 struct cftype_set base_cftset;
624 /* should be defined only by modular subsystems */
625 struct module *module;
628 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
629 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
630 #include <linux/cgroup_subsys.h>
631 #undef IS_SUBSYS_ENABLED
635 * css_parent - find the parent css
636 * @css: the target cgroup_subsys_state
638 * Return the parent css of @css. This function is guaranteed to return
639 * non-NULL parent as long as @css isn't the root.
642 struct cgroup_subsys_state *css_parent(struct cgroup_subsys_state *css)
648 * task_css_set_check - obtain a task's css_set with extra access conditions
649 * @task: the task to obtain css_set for
650 * @__c: extra condition expression to be passed to rcu_dereference_check()
652 * A task's css_set is RCU protected, initialized and exited while holding
653 * task_lock(), and can only be modified while holding both cgroup_mutex
654 * and task_lock() while the task is alive. This macro verifies that the
655 * caller is inside proper critical section and returns @task's css_set.
657 * The caller can also specify additional allowed conditions via @__c, such
658 * as locks used during the cgroup_subsys::attach() methods.
660 #ifdef CONFIG_PROVE_RCU
661 extern struct mutex cgroup_mutex;
662 #define task_css_set_check(task, __c) \
663 rcu_dereference_check((task)->cgroups, \
664 lockdep_is_held(&(task)->alloc_lock) || \
665 lockdep_is_held(&cgroup_mutex) || (__c))
667 #define task_css_set_check(task, __c) \
668 rcu_dereference((task)->cgroups)
672 * task_css_check - obtain css for (task, subsys) w/ extra access conds
673 * @task: the target task
674 * @subsys_id: the target subsystem ID
675 * @__c: extra condition expression to be passed to rcu_dereference_check()
677 * Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The
678 * synchronization rules are the same as task_css_set_check().
680 #define task_css_check(task, subsys_id, __c) \
681 task_css_set_check((task), (__c))->subsys[(subsys_id)]
684 * task_css_set - obtain a task's css_set
685 * @task: the task to obtain css_set for
687 * See task_css_set_check().
689 static inline struct css_set *task_css_set(struct task_struct *task)
691 return task_css_set_check(task, false);
695 * task_css - obtain css for (task, subsys)
696 * @task: the target task
697 * @subsys_id: the target subsystem ID
699 * See task_css_check().
701 static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
704 return task_css_check(task, subsys_id, false);
707 static inline struct cgroup *task_cgroup(struct task_struct *task,
710 return task_css(task, subsys_id)->cgroup;
713 struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
714 struct cgroup_subsys_state *parent);
716 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
719 * css_for_each_child - iterate through children of a css
720 * @pos: the css * to use as the loop cursor
721 * @parent: css whose children to walk
723 * Walk @parent's children. Must be called under rcu_read_lock(). A child
724 * css which hasn't finished ->css_online() or already has finished
725 * ->css_offline() may show up during traversal and it's each subsystem's
726 * responsibility to verify that each @pos is alive.
728 * If a subsystem synchronizes against the parent in its ->css_online() and
729 * before starting iterating, a css which finished ->css_online() is
730 * guaranteed to be visible in the future iterations.
732 * It is allowed to temporarily drop RCU read lock during iteration. The
733 * caller is responsible for ensuring that @pos remains accessible until
734 * the start of the next iteration by, for example, bumping the css refcnt.
736 #define css_for_each_child(pos, parent) \
737 for ((pos) = css_next_child(NULL, (parent)); (pos); \
738 (pos) = css_next_child((pos), (parent)))
740 struct cgroup_subsys_state *
741 css_next_descendant_pre(struct cgroup_subsys_state *pos,
742 struct cgroup_subsys_state *css);
744 struct cgroup_subsys_state *
745 css_rightmost_descendant(struct cgroup_subsys_state *pos);
748 * css_for_each_descendant_pre - pre-order walk of a css's descendants
749 * @pos: the css * to use as the loop cursor
750 * @root: css whose descendants to walk
752 * Walk @root's descendants. @root is included in the iteration and the
753 * first node to be visited. Must be called under rcu_read_lock(). A
754 * descendant css which hasn't finished ->css_online() or already has
755 * finished ->css_offline() may show up during traversal and it's each
756 * subsystem's responsibility to verify that each @pos is alive.
758 * If a subsystem synchronizes against the parent in its ->css_online() and
759 * before starting iterating, and synchronizes against @pos on each
760 * iteration, any descendant css which finished ->css_online() is
761 * guaranteed to be visible in the future iterations.
763 * In other words, the following guarantees that a descendant can't escape
764 * state updates of its ancestors.
768 * Lock @css's parent and @css;
769 * Inherit state from the parent;
773 * my_update_state(@css)
775 * css_for_each_descendant_pre(@pos, @css) {
778 * Update @css's state;
780 * Verify @pos is alive and inherit state from its parent;
785 * As long as the inheriting step, including checking the parent state, is
786 * enclosed inside @pos locking, double-locking the parent isn't necessary
787 * while inheriting. The state update to the parent is guaranteed to be
788 * visible by walking order and, as long as inheriting operations to the
789 * same @pos are atomic to each other, multiple updates racing each other
790 * still result in the correct state. It's guaranateed that at least one
791 * inheritance happens for any css after the latest update to its parent.
793 * If checking parent's state requires locking the parent, each inheriting
794 * iteration should lock and unlock both @pos->parent and @pos.
796 * Alternatively, a subsystem may choose to use a single global lock to
797 * synchronize ->css_online() and ->css_offline() against tree-walking
800 * It is allowed to temporarily drop RCU read lock during iteration. The
801 * caller is responsible for ensuring that @pos remains accessible until
802 * the start of the next iteration by, for example, bumping the css refcnt.
804 #define css_for_each_descendant_pre(pos, css) \
805 for ((pos) = css_next_descendant_pre(NULL, (css)); (pos); \
806 (pos) = css_next_descendant_pre((pos), (css)))
808 struct cgroup_subsys_state *
809 css_next_descendant_post(struct cgroup_subsys_state *pos,
810 struct cgroup_subsys_state *css);
813 * css_for_each_descendant_post - post-order walk of a css's descendants
814 * @pos: the css * to use as the loop cursor
815 * @css: css whose descendants to walk
817 * Similar to css_for_each_descendant_pre() but performs post-order
818 * traversal instead. @root is included in the iteration and the last
819 * node to be visited. Note that the walk visibility guarantee described
820 * in pre-order walk doesn't apply the same to post-order walks.
822 #define css_for_each_descendant_post(pos, css) \
823 for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \
824 (pos) = css_next_descendant_post((pos), (css)))
826 /* A css_task_iter should be treated as an opaque object */
827 struct css_task_iter {
828 struct cgroup_subsys_state *origin_css;
829 struct list_head *cset_link;
830 struct list_head *task;
833 void css_task_iter_start(struct cgroup_subsys_state *css,
834 struct css_task_iter *it);
835 struct task_struct *css_task_iter_next(struct css_task_iter *it);
836 void css_task_iter_end(struct css_task_iter *it);
838 int css_scan_tasks(struct cgroup_subsys_state *css,
839 bool (*test)(struct task_struct *, void *),
840 void (*process)(struct task_struct *, void *),
841 void *data, struct ptr_heap *heap);
843 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
844 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
846 struct cgroup_subsys_state *css_from_dir(struct dentry *dentry,
847 struct cgroup_subsys *ss);
849 #else /* !CONFIG_CGROUPS */
851 static inline int cgroup_init_early(void) { return 0; }
852 static inline int cgroup_init(void) { return 0; }
853 static inline void cgroup_fork(struct task_struct *p) {}
854 static inline void cgroup_post_fork(struct task_struct *p) {}
855 static inline void cgroup_exit(struct task_struct *p, int callbacks) {}
857 static inline int cgroupstats_build(struct cgroupstats *stats,
858 struct dentry *dentry)
863 /* No cgroups - nothing to do */
864 static inline int cgroup_attach_task_all(struct task_struct *from,
865 struct task_struct *t)
870 #endif /* !CONFIG_CGROUPS */
872 #endif /* _LINUX_CGROUP_H */