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>
24 #include <linux/seq_file.h>
34 extern int cgroup_init_early(void);
35 extern int cgroup_init(void);
36 extern void cgroup_fork(struct task_struct *p);
37 extern void cgroup_post_fork(struct task_struct *p);
38 extern void cgroup_exit(struct task_struct *p, int run_callbacks);
39 extern int cgroupstats_build(struct cgroupstats *stats,
40 struct dentry *dentry);
41 extern int cgroup_load_subsys(struct cgroup_subsys *ss);
42 extern void cgroup_unload_subsys(struct cgroup_subsys *ss);
44 extern int proc_cgroup_show(struct seq_file *, void *);
47 * Define the enumeration of all cgroup subsystems.
49 * We define ids for builtin subsystems and then modular ones.
51 #define SUBSYS(_x) _x ## _subsys_id,
52 enum cgroup_subsys_id {
53 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
54 #include <linux/cgroup_subsys.h>
55 #undef IS_SUBSYS_ENABLED
56 CGROUP_BUILTIN_SUBSYS_COUNT,
58 __CGROUP_SUBSYS_TEMP_PLACEHOLDER = CGROUP_BUILTIN_SUBSYS_COUNT - 1,
60 #define IS_SUBSYS_ENABLED(option) IS_MODULE(option)
61 #include <linux/cgroup_subsys.h>
62 #undef IS_SUBSYS_ENABLED
67 /* Per-subsystem/per-cgroup state maintained by the system. */
68 struct cgroup_subsys_state {
69 /* the cgroup that this css is attached to */
70 struct cgroup *cgroup;
72 /* the cgroup subsystem that this css is attached to */
73 struct cgroup_subsys *ss;
75 /* reference count - access via css_[try]get() and css_put() */
76 struct percpu_ref refcnt;
79 struct cgroup_subsys_state *parent;
82 /* ID for this css, if possible */
83 struct css_id __rcu *id;
85 /* percpu_ref killing and RCU release */
86 struct rcu_head rcu_head;
87 struct work_struct destroy_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() */
97 * css_get - obtain a reference on the specified css
100 * The caller must already have a reference.
102 static inline void css_get(struct cgroup_subsys_state *css)
104 /* We don't need to reference count the root state */
105 if (!(css->flags & CSS_ROOT))
106 percpu_ref_get(&css->refcnt);
110 * css_tryget - try to obtain a reference on the specified css
113 * Obtain a reference on @css if it's alive. The caller naturally needs to
114 * ensure that @css is accessible but doesn't have to be holding a
115 * reference on it - IOW, RCU protected access is good enough for this
116 * function. Returns %true if a reference count was successfully obtained;
119 static inline bool css_tryget(struct cgroup_subsys_state *css)
121 if (css->flags & CSS_ROOT)
123 return percpu_ref_tryget(&css->refcnt);
127 * css_put - put a css reference
130 * Put a reference obtained via css_get() and css_tryget().
132 static inline void css_put(struct cgroup_subsys_state *css)
134 if (!(css->flags & CSS_ROOT))
135 percpu_ref_put(&css->refcnt);
138 /* bits in struct cgroup flags field */
140 /* Control Group is dead */
143 * Control Group has previously had a child cgroup or a task,
144 * but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
147 /* Control Group requires release notifications to userspace */
148 CGRP_NOTIFY_ON_RELEASE,
150 * Clone the parent's configuration when creating a new child
151 * cpuset cgroup. For historical reasons, this option can be
152 * specified at mount time and thus is implemented here.
154 CGRP_CPUSET_CLONE_CHILDREN,
155 /* see the comment above CGRP_ROOT_SANE_BEHAVIOR for details */
160 struct rcu_head rcu_head;
165 unsigned long flags; /* "unsigned long" so bitops work */
168 * idr allocated in-hierarchy ID.
170 * The ID of the root cgroup is always 0, and a new cgroup
171 * will be assigned with a smallest available ID.
175 /* the number of attached css's */
179 * We link our 'sibling' struct into our parent's 'children'.
180 * Our children link their 'sibling' into our 'children'.
182 struct list_head sibling; /* my parent's children */
183 struct list_head children; /* my children */
184 struct list_head files; /* my files */
186 struct cgroup *parent; /* my parent */
187 struct dentry *dentry; /* cgroup fs entry, RCU protected */
190 * Monotonically increasing unique serial number which defines a
191 * uniform order among all cgroups. It's guaranteed that all
192 * ->children lists are in the ascending order of ->serial_nr.
193 * It's used to allow interrupting and resuming iterations.
198 * This is a copy of dentry->d_name, and it's needed because
199 * we can't use dentry->d_name in cgroup_path().
201 * You must acquire rcu_read_lock() to access cgrp->name, and
202 * the only place that can change it is rename(), which is
203 * protected by parent dir's i_mutex.
205 * Normally you should use cgroup_name() wrapper rather than
206 * access it directly.
208 struct cgroup_name __rcu *name;
210 /* Private pointers for each registered subsystem */
211 struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
213 struct cgroupfs_root *root;
216 * List of cgrp_cset_links pointing at css_sets with tasks in this
217 * cgroup. Protected by css_set_lock.
219 struct list_head cset_links;
222 * Linked list running through all cgroups that can
223 * potentially be reaped by the release agent. Protected by
226 struct list_head release_list;
229 * list of pidlists, up to two for each namespace (one for procs, one
230 * for tasks); created on demand.
232 struct list_head pidlists;
233 struct mutex pidlist_mutex;
235 /* dummy css with NULL ->ss, points back to this cgroup */
236 struct cgroup_subsys_state dummy_css;
238 /* For css percpu_ref killing and RCU-protected deletion */
239 struct rcu_head rcu_head;
240 struct work_struct destroy_work;
242 /* directory xattrs */
243 struct simple_xattrs xattrs;
246 #define MAX_CGROUP_ROOT_NAMELEN 64
248 /* cgroupfs_root->flags */
251 * Unfortunately, cgroup core and various controllers are riddled
252 * with idiosyncrasies and pointless options. The following flag,
253 * when set, will force sane behavior - some options are forced on,
254 * others are disallowed, and some controllers will change their
255 * hierarchical or other behaviors.
257 * The set of behaviors affected by this flag are still being
258 * determined and developed and the mount option for this flag is
259 * prefixed with __DEVEL__. The prefix will be dropped once we
260 * reach the point where all behaviors are compatible with the
261 * planned unified hierarchy, which will automatically turn on this
264 * The followings are the behaviors currently affected this flag.
266 * - Mount options "noprefix" and "clone_children" are disallowed.
267 * Also, cgroupfs file cgroup.clone_children is not created.
269 * - When mounting an existing superblock, mount options should
272 * - Remount is disallowed.
274 * - rename(2) is disallowed.
276 * - "tasks" is removed. Everything should be at process
277 * granularity. Use "cgroup.procs" instead.
279 * - "cgroup.procs" is not sorted. pids will be unique unless they
280 * got recycled inbetween reads.
282 * - "release_agent" and "notify_on_release" are removed.
283 * Replacement notification mechanism will be implemented.
285 * - cpuset: tasks will be kept in empty cpusets when hotplug happens
286 * and take masks of ancestors with non-empty cpus/mems, instead of
287 * being moved to an ancestor.
289 * - cpuset: a task can be moved into an empty cpuset, and again it
290 * takes masks of ancestors.
292 * - memcg: use_hierarchy is on by default and the cgroup file for
293 * the flag is not created.
295 * - blkcg: blk-throttle becomes properly hierarchical.
297 CGRP_ROOT_SANE_BEHAVIOR = (1 << 0),
299 CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
300 CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
302 /* mount options live below bit 16 */
303 CGRP_ROOT_OPTION_MASK = (1 << 16) - 1,
305 CGRP_ROOT_SUBSYS_BOUND = (1 << 16), /* subsystems finished binding */
309 * A cgroupfs_root represents the root of a cgroup hierarchy, and may be
310 * associated with a superblock to form an active hierarchy. This is
311 * internal to cgroup core. Don't access directly from controllers.
313 struct cgroupfs_root {
314 struct super_block *sb;
316 /* The bitmask of subsystems attached to this hierarchy */
317 unsigned long subsys_mask;
319 /* Unique id for this hierarchy. */
322 /* A list running through the attached subsystems */
323 struct list_head subsys_list;
325 /* The root cgroup for this hierarchy */
326 struct cgroup top_cgroup;
328 /* Tracks how many cgroups are currently defined in hierarchy.*/
329 int number_of_cgroups;
331 /* A list running through the active hierarchies */
332 struct list_head root_list;
334 /* Hierarchy-specific flags */
337 /* IDs for cgroups in this hierarchy */
338 struct idr cgroup_idr;
340 /* The path to use for release notifications. */
341 char release_agent_path[PATH_MAX];
343 /* The name for this hierarchy - may be empty */
344 char name[MAX_CGROUP_ROOT_NAMELEN];
348 * A css_set is a structure holding pointers to a set of
349 * cgroup_subsys_state objects. This saves space in the task struct
350 * object and speeds up fork()/exit(), since a single inc/dec and a
351 * list_add()/del() can bump the reference count on the entire cgroup
357 /* Reference count */
361 * List running through all cgroup groups in the same hash
362 * slot. Protected by css_set_lock
364 struct hlist_node hlist;
367 * List running through all tasks using this cgroup
368 * group. Protected by css_set_lock
370 struct list_head tasks;
373 * List of cgrp_cset_links pointing at cgroups referenced from this
374 * css_set. Protected by css_set_lock.
376 struct list_head cgrp_links;
379 * Set of subsystem states, one for each subsystem. This array
380 * is immutable after creation apart from the init_css_set
381 * during subsystem registration (at boot time) and modular subsystem
384 struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
386 /* For RCU-protected deletion */
387 struct rcu_head rcu_head;
391 * struct cftype: handler definitions for cgroup control files
393 * When reading/writing to a file:
394 * - the cgroup to use is file->f_dentry->d_parent->d_fsdata
395 * - the 'cftype' of the file is file->f_dentry->d_fsdata
400 CFTYPE_ONLY_ON_ROOT = (1 << 0), /* only create on root cgrp */
401 CFTYPE_NOT_ON_ROOT = (1 << 1), /* don't create on root cgrp */
402 CFTYPE_INSANE = (1 << 2), /* don't create if sane_behavior */
403 CFTYPE_NO_PREFIX = (1 << 3), /* (DON'T USE FOR NEW FILES) no subsys prefix */
406 #define MAX_CFTYPE_NAME 64
410 * By convention, the name should begin with the name of the
411 * subsystem, followed by a period. Zero length string indicates
412 * end of cftype array.
414 char name[MAX_CFTYPE_NAME];
417 * If not 0, file mode is set to this value, otherwise it will
418 * be figured out automatically
423 * If non-zero, defines the maximum length of string that can
424 * be passed to write_string; defaults to 64
426 size_t max_write_len;
432 * The subsys this file belongs to. Initialized automatically
433 * during registration. NULL for cgroup core files.
435 struct cgroup_subsys *ss;
437 int (*open)(struct inode *inode, struct file *file);
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_subsys_state *css, struct cftype *cft);
444 * read_s64() is a signed version of read_u64()
446 s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft);
448 * read_seq_string() is used for outputting a simple sequence
451 int (*read_seq_string)(struct cgroup_subsys_state *css,
452 struct cftype *cft, struct seq_file *m);
455 * write_u64() is a shortcut for the common case of accepting
456 * a single integer (as parsed by simple_strtoull) from
457 * userspace. Use in place of write(); return 0 or error.
459 int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft,
462 * write_s64() is a signed version of write_u64()
464 int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft,
468 * write_string() is passed a nul-terminated kernelspace
469 * buffer of maximum length determined by max_write_len.
470 * Returns 0 or -ve error code.
472 int (*write_string)(struct cgroup_subsys_state *css, struct cftype *cft,
475 * trigger() callback can be used to get some kick from the
476 * userspace, when the actual string written is not important
477 * at all. The private field can be used to determine the
478 * kick type for multiplexing.
480 int (*trigger)(struct cgroup_subsys_state *css, unsigned int event);
484 * cftype_sets describe cftypes belonging to a subsystem and are chained at
485 * cgroup_subsys->cftsets. Each cftset points to an array of cftypes
486 * terminated by zero length name.
489 struct list_head node; /* chained at subsys->cftsets */
494 * cgroupfs file entry, pointed to from leaf dentry->d_fsdata. Don't
498 struct list_head node;
499 struct dentry *dentry;
501 struct cgroup_subsys_state *css;
504 struct simple_xattrs xattrs;
507 /* seq_file->private points to the following, only ->priv is public */
508 struct cgroup_open_file {
514 * See the comment above CGRP_ROOT_SANE_BEHAVIOR for details. This
515 * function can be called as long as @cgrp is accessible.
517 static inline bool cgroup_sane_behavior(const struct cgroup *cgrp)
519 return cgrp->root->flags & CGRP_ROOT_SANE_BEHAVIOR;
522 /* Caller should hold rcu_read_lock() */
523 static inline const char *cgroup_name(const struct cgroup *cgrp)
525 return rcu_dereference(cgrp->name)->name;
528 static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq)
530 struct cgroup_open_file *of = seq->private;
534 static inline struct cftype *seq_cft(struct seq_file *seq)
536 struct cgroup_open_file *of = seq->private;
537 return of->cfe->type;
540 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
541 int cgroup_rm_cftypes(struct cftype *cfts);
543 bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
545 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
546 int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
548 int cgroup_task_count(const struct cgroup *cgrp);
551 * Control Group taskset, used to pass around set of tasks to cgroup_subsys
554 struct cgroup_taskset;
555 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
556 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
557 struct cgroup_subsys_state *cgroup_taskset_cur_css(struct cgroup_taskset *tset,
559 int cgroup_taskset_size(struct cgroup_taskset *tset);
562 * cgroup_taskset_for_each - iterate cgroup_taskset
563 * @task: the loop cursor
564 * @skip_css: skip if task's css matches this, %NULL to iterate through all
565 * @tset: taskset to iterate
567 #define cgroup_taskset_for_each(task, skip_css, tset) \
568 for ((task) = cgroup_taskset_first((tset)); (task); \
569 (task) = cgroup_taskset_next((tset))) \
571 cgroup_taskset_cur_css((tset), \
572 (skip_css)->ss->subsys_id) != (skip_css))
575 * Control Group subsystem type.
576 * See Documentation/cgroups/cgroups.txt for details
579 struct cgroup_subsys {
580 struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);
581 int (*css_online)(struct cgroup_subsys_state *css);
582 void (*css_offline)(struct cgroup_subsys_state *css);
583 void (*css_free)(struct cgroup_subsys_state *css);
585 int (*can_attach)(struct cgroup_subsys_state *css,
586 struct cgroup_taskset *tset);
587 void (*cancel_attach)(struct cgroup_subsys_state *css,
588 struct cgroup_taskset *tset);
589 void (*attach)(struct cgroup_subsys_state *css,
590 struct cgroup_taskset *tset);
591 void (*fork)(struct task_struct *task);
592 void (*exit)(struct cgroup_subsys_state *css,
593 struct cgroup_subsys_state *old_css,
594 struct task_struct *task);
595 void (*bind)(struct cgroup_subsys_state *root_css);
602 * If %false, this subsystem is properly hierarchical -
603 * configuration, resource accounting and restriction on a parent
604 * cgroup cover those of its children. If %true, hierarchy support
605 * is broken in some ways - some subsystems ignore hierarchy
606 * completely while others are only implemented half-way.
608 * It's now disallowed to create nested cgroups if the subsystem is
609 * broken and cgroup core will emit a warning message on such
610 * cases. Eventually, all subsystems will be made properly
611 * hierarchical and this will go away.
613 bool broken_hierarchy;
614 bool warned_broken_hierarchy;
616 #define MAX_CGROUP_TYPE_NAMELEN 32
620 * Link to parent, and list entry in parent's children.
621 * Protected by cgroup_lock()
623 struct cgroupfs_root *root;
624 struct list_head sibling;
626 /* list of cftype_sets */
627 struct list_head cftsets;
629 /* base cftypes, automatically [de]registered with subsys itself */
630 struct cftype *base_cftypes;
631 struct cftype_set base_cftset;
633 /* should be defined only by modular subsystems */
634 struct module *module;
637 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
638 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
639 #include <linux/cgroup_subsys.h>
640 #undef IS_SUBSYS_ENABLED
644 * css_parent - find the parent css
645 * @css: the target cgroup_subsys_state
647 * Return the parent css of @css. This function is guaranteed to return
648 * non-NULL parent as long as @css isn't the root.
651 struct cgroup_subsys_state *css_parent(struct cgroup_subsys_state *css)
657 * task_css_set_check - obtain a task's css_set with extra access conditions
658 * @task: the task to obtain css_set for
659 * @__c: extra condition expression to be passed to rcu_dereference_check()
661 * A task's css_set is RCU protected, initialized and exited while holding
662 * task_lock(), and can only be modified while holding both cgroup_mutex
663 * and task_lock() while the task is alive. This macro verifies that the
664 * caller is inside proper critical section and returns @task's css_set.
666 * The caller can also specify additional allowed conditions via @__c, such
667 * as locks used during the cgroup_subsys::attach() methods.
669 #ifdef CONFIG_PROVE_RCU
670 extern struct mutex cgroup_mutex;
671 #define task_css_set_check(task, __c) \
672 rcu_dereference_check((task)->cgroups, \
673 lockdep_is_held(&(task)->alloc_lock) || \
674 lockdep_is_held(&cgroup_mutex) || (__c))
676 #define task_css_set_check(task, __c) \
677 rcu_dereference((task)->cgroups)
681 * task_css_check - obtain css for (task, subsys) w/ extra access conds
682 * @task: the target task
683 * @subsys_id: the target subsystem ID
684 * @__c: extra condition expression to be passed to rcu_dereference_check()
686 * Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The
687 * synchronization rules are the same as task_css_set_check().
689 #define task_css_check(task, subsys_id, __c) \
690 task_css_set_check((task), (__c))->subsys[(subsys_id)]
693 * task_css_set - obtain a task's css_set
694 * @task: the task to obtain css_set for
696 * See task_css_set_check().
698 static inline struct css_set *task_css_set(struct task_struct *task)
700 return task_css_set_check(task, false);
704 * task_css - obtain css for (task, subsys)
705 * @task: the target task
706 * @subsys_id: the target subsystem ID
708 * See task_css_check().
710 static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
713 return task_css_check(task, subsys_id, false);
716 static inline struct cgroup *task_cgroup(struct task_struct *task,
719 return task_css(task, subsys_id)->cgroup;
722 struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
723 struct cgroup_subsys_state *parent);
725 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
728 * css_for_each_child - iterate through children of a css
729 * @pos: the css * to use as the loop cursor
730 * @parent: css whose children to walk
732 * Walk @parent's children. Must be called under rcu_read_lock(). A child
733 * css which hasn't finished ->css_online() or already has finished
734 * ->css_offline() may show up during traversal and it's each subsystem's
735 * responsibility to verify that each @pos is alive.
737 * If a subsystem synchronizes against the parent in its ->css_online() and
738 * before starting iterating, a css which finished ->css_online() is
739 * guaranteed to be visible in the future iterations.
741 * It is allowed to temporarily drop RCU read lock during iteration. The
742 * caller is responsible for ensuring that @pos remains accessible until
743 * the start of the next iteration by, for example, bumping the css refcnt.
745 #define css_for_each_child(pos, parent) \
746 for ((pos) = css_next_child(NULL, (parent)); (pos); \
747 (pos) = css_next_child((pos), (parent)))
749 struct cgroup_subsys_state *
750 css_next_descendant_pre(struct cgroup_subsys_state *pos,
751 struct cgroup_subsys_state *css);
753 struct cgroup_subsys_state *
754 css_rightmost_descendant(struct cgroup_subsys_state *pos);
757 * css_for_each_descendant_pre - pre-order walk of a css's descendants
758 * @pos: the css * to use as the loop cursor
759 * @root: css whose descendants to walk
761 * Walk @root's descendants. @root is included in the iteration and the
762 * first node to be visited. Must be called under rcu_read_lock(). A
763 * descendant css which hasn't finished ->css_online() or already has
764 * finished ->css_offline() may show up during traversal and it's each
765 * subsystem's responsibility to verify that each @pos is alive.
767 * If a subsystem synchronizes against the parent in its ->css_online() and
768 * before starting iterating, and synchronizes against @pos on each
769 * iteration, any descendant css which finished ->css_online() is
770 * guaranteed to be visible in the future iterations.
772 * In other words, the following guarantees that a descendant can't escape
773 * state updates of its ancestors.
777 * Lock @css's parent and @css;
778 * Inherit state from the parent;
782 * my_update_state(@css)
784 * css_for_each_descendant_pre(@pos, @css) {
787 * Update @css's state;
789 * Verify @pos is alive and inherit state from its parent;
794 * As long as the inheriting step, including checking the parent state, is
795 * enclosed inside @pos locking, double-locking the parent isn't necessary
796 * while inheriting. The state update to the parent is guaranteed to be
797 * visible by walking order and, as long as inheriting operations to the
798 * same @pos are atomic to each other, multiple updates racing each other
799 * still result in the correct state. It's guaranateed that at least one
800 * inheritance happens for any css after the latest update to its parent.
802 * If checking parent's state requires locking the parent, each inheriting
803 * iteration should lock and unlock both @pos->parent and @pos.
805 * Alternatively, a subsystem may choose to use a single global lock to
806 * synchronize ->css_online() and ->css_offline() against tree-walking
809 * It is allowed to temporarily drop RCU read lock during iteration. The
810 * caller is responsible for ensuring that @pos remains accessible until
811 * the start of the next iteration by, for example, bumping the css refcnt.
813 #define css_for_each_descendant_pre(pos, css) \
814 for ((pos) = css_next_descendant_pre(NULL, (css)); (pos); \
815 (pos) = css_next_descendant_pre((pos), (css)))
817 struct cgroup_subsys_state *
818 css_next_descendant_post(struct cgroup_subsys_state *pos,
819 struct cgroup_subsys_state *css);
822 * css_for_each_descendant_post - post-order walk of a css's descendants
823 * @pos: the css * to use as the loop cursor
824 * @css: css whose descendants to walk
826 * Similar to css_for_each_descendant_pre() but performs post-order
827 * traversal instead. @root is included in the iteration and the last
828 * node to be visited. Note that the walk visibility guarantee described
829 * in pre-order walk doesn't apply the same to post-order walks.
831 #define css_for_each_descendant_post(pos, css) \
832 for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \
833 (pos) = css_next_descendant_post((pos), (css)))
835 /* A css_task_iter should be treated as an opaque object */
836 struct css_task_iter {
837 struct cgroup_subsys_state *origin_css;
838 struct list_head *cset_link;
839 struct list_head *task;
842 void css_task_iter_start(struct cgroup_subsys_state *css,
843 struct css_task_iter *it);
844 struct task_struct *css_task_iter_next(struct css_task_iter *it);
845 void css_task_iter_end(struct css_task_iter *it);
847 int css_scan_tasks(struct cgroup_subsys_state *css,
848 bool (*test)(struct task_struct *, void *),
849 void (*process)(struct task_struct *, void *),
850 void *data, struct ptr_heap *heap);
852 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
853 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
855 struct cgroup_subsys_state *css_from_dir(struct dentry *dentry,
856 struct cgroup_subsys *ss);
858 #else /* !CONFIG_CGROUPS */
860 static inline int cgroup_init_early(void) { return 0; }
861 static inline int cgroup_init(void) { return 0; }
862 static inline void cgroup_fork(struct task_struct *p) {}
863 static inline void cgroup_post_fork(struct task_struct *p) {}
864 static inline void cgroup_exit(struct task_struct *p, int callbacks) {}
866 static inline int cgroupstats_build(struct cgroupstats *stats,
867 struct dentry *dentry)
872 /* No cgroups - nothing to do */
873 static inline int cgroup_attach_task_all(struct task_struct *from,
874 struct task_struct *t)
879 #endif /* !CONFIG_CGROUPS */
881 #endif /* _LINUX_CGROUP_H */