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>
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 /* List of events which userspace want to receive */
243 struct list_head event_list;
244 spinlock_t event_list_lock;
246 /* directory xattrs */
247 struct simple_xattrs xattrs;
250 #define MAX_CGROUP_ROOT_NAMELEN 64
252 /* cgroupfs_root->flags */
255 * Unfortunately, cgroup core and various controllers are riddled
256 * with idiosyncrasies and pointless options. The following flag,
257 * when set, will force sane behavior - some options are forced on,
258 * others are disallowed, and some controllers will change their
259 * hierarchical or other behaviors.
261 * The set of behaviors affected by this flag are still being
262 * determined and developed and the mount option for this flag is
263 * prefixed with __DEVEL__. The prefix will be dropped once we
264 * reach the point where all behaviors are compatible with the
265 * planned unified hierarchy, which will automatically turn on this
268 * The followings are the behaviors currently affected this flag.
270 * - Mount options "noprefix" and "clone_children" are disallowed.
271 * Also, cgroupfs file cgroup.clone_children is not created.
273 * - When mounting an existing superblock, mount options should
276 * - Remount is disallowed.
278 * - rename(2) is disallowed.
280 * - "tasks" is removed. Everything should be at process
281 * granularity. Use "cgroup.procs" instead.
283 * - "release_agent" and "notify_on_release" are removed.
284 * Replacement notification mechanism will be implemented.
286 * - cpuset: tasks will be kept in empty cpusets when hotplug happens
287 * and take masks of ancestors with non-empty cpus/mems, instead of
288 * being moved to an ancestor.
290 * - cpuset: a task can be moved into an empty cpuset, and again it
291 * takes masks of ancestors.
293 * - memcg: use_hierarchy is on by default and the cgroup file for
294 * the flag is not created.
296 * - blkcg: blk-throttle becomes properly hierarchical.
298 CGRP_ROOT_SANE_BEHAVIOR = (1 << 0),
300 CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
301 CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
303 /* mount options live below bit 16 */
304 CGRP_ROOT_OPTION_MASK = (1 << 16) - 1,
306 CGRP_ROOT_SUBSYS_BOUND = (1 << 16), /* subsystems finished binding */
310 * A cgroupfs_root represents the root of a cgroup hierarchy, and may be
311 * associated with a superblock to form an active hierarchy. This is
312 * internal to cgroup core. Don't access directly from controllers.
314 struct cgroupfs_root {
315 struct super_block *sb;
317 /* The bitmask of subsystems attached to this hierarchy */
318 unsigned long subsys_mask;
320 /* Unique id for this hierarchy. */
323 /* A list running through the attached subsystems */
324 struct list_head subsys_list;
326 /* The root cgroup for this hierarchy */
327 struct cgroup top_cgroup;
329 /* Tracks how many cgroups are currently defined in hierarchy.*/
330 int number_of_cgroups;
332 /* A list running through the active hierarchies */
333 struct list_head root_list;
335 /* Hierarchy-specific flags */
338 /* IDs for cgroups in this hierarchy */
339 struct idr cgroup_idr;
341 /* The path to use for release notifications. */
342 char release_agent_path[PATH_MAX];
344 /* The name for this hierarchy - may be empty */
345 char name[MAX_CGROUP_ROOT_NAMELEN];
349 * A css_set is a structure holding pointers to a set of
350 * cgroup_subsys_state objects. This saves space in the task struct
351 * object and speeds up fork()/exit(), since a single inc/dec and a
352 * list_add()/del() can bump the reference count on the entire cgroup
358 /* Reference count */
362 * List running through all cgroup groups in the same hash
363 * slot. Protected by css_set_lock
365 struct hlist_node hlist;
368 * List running through all tasks using this cgroup
369 * group. Protected by css_set_lock
371 struct list_head tasks;
374 * List of cgrp_cset_links pointing at cgroups referenced from this
375 * css_set. Protected by css_set_lock.
377 struct list_head cgrp_links;
380 * Set of subsystem states, one for each subsystem. This array
381 * is immutable after creation apart from the init_css_set
382 * during subsystem registration (at boot time) and modular subsystem
385 struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
387 /* For RCU-protected deletion */
388 struct rcu_head rcu_head;
392 * cgroup_map_cb is an abstract callback API for reporting map-valued
396 struct cgroup_map_cb {
397 int (*fill)(struct cgroup_map_cb *cb, const char *key, u64 value);
402 * struct cftype: handler definitions for cgroup control files
404 * When reading/writing to a file:
405 * - the cgroup to use is file->f_dentry->d_parent->d_fsdata
406 * - the 'cftype' of the file is file->f_dentry->d_fsdata
411 CFTYPE_ONLY_ON_ROOT = (1 << 0), /* only create on root cgrp */
412 CFTYPE_NOT_ON_ROOT = (1 << 1), /* don't create on root cgrp */
413 CFTYPE_INSANE = (1 << 2), /* don't create if sane_behavior */
416 #define MAX_CFTYPE_NAME 64
420 * By convention, the name should begin with the name of the
421 * subsystem, followed by a period. Zero length string indicates
422 * end of cftype array.
424 char name[MAX_CFTYPE_NAME];
427 * If not 0, file mode is set to this value, otherwise it will
428 * be figured out automatically
433 * If non-zero, defines the maximum length of string that can
434 * be passed to write_string; defaults to 64
436 size_t max_write_len;
442 * The subsys this file belongs to. Initialized automatically
443 * during registration. NULL for cgroup core files.
445 struct cgroup_subsys *ss;
447 int (*open)(struct inode *inode, struct file *file);
448 ssize_t (*read)(struct cgroup_subsys_state *css, struct cftype *cft,
450 char __user *buf, size_t nbytes, loff_t *ppos);
452 * read_u64() is a shortcut for the common case of returning a
453 * single integer. Use it in place of read()
455 u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft);
457 * read_s64() is a signed version of read_u64()
459 s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft);
461 * read_map() is used for defining a map of key/value
462 * pairs. It should call cb->fill(cb, key, value) for each
463 * entry. The key/value pairs (and their ordering) should not
464 * change between reboots.
466 int (*read_map)(struct cgroup_subsys_state *css, struct cftype *cft,
467 struct cgroup_map_cb *cb);
469 * read_seq_string() is used for outputting a simple sequence
472 int (*read_seq_string)(struct cgroup_subsys_state *css,
473 struct cftype *cft, struct seq_file *m);
475 ssize_t (*write)(struct cgroup_subsys_state *css, struct cftype *cft,
477 const char __user *buf, size_t nbytes, loff_t *ppos);
480 * write_u64() is a shortcut for the common case of accepting
481 * a single integer (as parsed by simple_strtoull) from
482 * userspace. Use in place of write(); return 0 or error.
484 int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft,
487 * write_s64() is a signed version of write_u64()
489 int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft,
493 * write_string() is passed a nul-terminated kernelspace
494 * buffer of maximum length determined by max_write_len.
495 * Returns 0 or -ve error code.
497 int (*write_string)(struct cgroup_subsys_state *css, struct cftype *cft,
500 * trigger() callback can be used to get some kick from the
501 * userspace, when the actual string written is not important
502 * at all. The private field can be used to determine the
503 * kick type for multiplexing.
505 int (*trigger)(struct cgroup_subsys_state *css, unsigned int event);
507 int (*release)(struct inode *inode, struct file *file);
510 * register_event() callback will be used to add new userspace
511 * waiter for changes related to the cftype. Implement it if
512 * you want to provide this functionality. Use eventfd_signal()
513 * on eventfd to send notification to userspace.
515 int (*register_event)(struct cgroup_subsys_state *css,
516 struct cftype *cft, struct eventfd_ctx *eventfd,
519 * unregister_event() callback will be called when userspace
520 * closes the eventfd or on cgroup removing.
521 * This callback must be implemented, if you want provide
522 * notification functionality.
524 void (*unregister_event)(struct cgroup_subsys_state *css,
526 struct eventfd_ctx *eventfd);
530 * cftype_sets describe cftypes belonging to a subsystem and are chained at
531 * cgroup_subsys->cftsets. Each cftset points to an array of cftypes
532 * terminated by zero length name.
535 struct list_head node; /* chained at subsys->cftsets */
540 * See the comment above CGRP_ROOT_SANE_BEHAVIOR for details. This
541 * function can be called as long as @cgrp is accessible.
543 static inline bool cgroup_sane_behavior(const struct cgroup *cgrp)
545 return cgrp->root->flags & CGRP_ROOT_SANE_BEHAVIOR;
548 /* Caller should hold rcu_read_lock() */
549 static inline const char *cgroup_name(const struct cgroup *cgrp)
551 return rcu_dereference(cgrp->name)->name;
554 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
555 int cgroup_rm_cftypes(struct cftype *cfts);
557 bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
559 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
560 int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
562 int cgroup_task_count(const struct cgroup *cgrp);
565 * Control Group taskset, used to pass around set of tasks to cgroup_subsys
568 struct cgroup_taskset;
569 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
570 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
571 struct cgroup_subsys_state *cgroup_taskset_cur_css(struct cgroup_taskset *tset,
573 int cgroup_taskset_size(struct cgroup_taskset *tset);
576 * cgroup_taskset_for_each - iterate cgroup_taskset
577 * @task: the loop cursor
578 * @skip_css: skip if task's css matches this, %NULL to iterate through all
579 * @tset: taskset to iterate
581 #define cgroup_taskset_for_each(task, skip_css, tset) \
582 for ((task) = cgroup_taskset_first((tset)); (task); \
583 (task) = cgroup_taskset_next((tset))) \
585 cgroup_taskset_cur_css((tset), \
586 (skip_css)->ss->subsys_id) != (skip_css))
589 * Control Group subsystem type.
590 * See Documentation/cgroups/cgroups.txt for details
593 struct cgroup_subsys {
594 struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);
595 int (*css_online)(struct cgroup_subsys_state *css);
596 void (*css_offline)(struct cgroup_subsys_state *css);
597 void (*css_free)(struct cgroup_subsys_state *css);
599 int (*can_attach)(struct cgroup_subsys_state *css,
600 struct cgroup_taskset *tset);
601 void (*cancel_attach)(struct cgroup_subsys_state *css,
602 struct cgroup_taskset *tset);
603 void (*attach)(struct cgroup_subsys_state *css,
604 struct cgroup_taskset *tset);
605 void (*fork)(struct task_struct *task);
606 void (*exit)(struct cgroup_subsys_state *css,
607 struct cgroup_subsys_state *old_css,
608 struct task_struct *task);
609 void (*bind)(struct cgroup_subsys_state *root_css);
615 * True if this subsys uses ID. ID is not available before cgroup_init()
616 * (not available in early_init time.)
621 * If %false, this subsystem is properly hierarchical -
622 * configuration, resource accounting and restriction on a parent
623 * cgroup cover those of its children. If %true, hierarchy support
624 * is broken in some ways - some subsystems ignore hierarchy
625 * completely while others are only implemented half-way.
627 * It's now disallowed to create nested cgroups if the subsystem is
628 * broken and cgroup core will emit a warning message on such
629 * cases. Eventually, all subsystems will be made properly
630 * hierarchical and this will go away.
632 bool broken_hierarchy;
633 bool warned_broken_hierarchy;
635 #define MAX_CGROUP_TYPE_NAMELEN 32
639 * Link to parent, and list entry in parent's children.
640 * Protected by cgroup_lock()
642 struct cgroupfs_root *root;
643 struct list_head sibling;
644 /* used when use_id == true */
648 /* list of cftype_sets */
649 struct list_head cftsets;
651 /* base cftypes, automatically [de]registered with subsys itself */
652 struct cftype *base_cftypes;
653 struct cftype_set base_cftset;
655 /* should be defined only by modular subsystems */
656 struct module *module;
659 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
660 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
661 #include <linux/cgroup_subsys.h>
662 #undef IS_SUBSYS_ENABLED
666 * css_parent - find the parent css
667 * @css: the target cgroup_subsys_state
669 * Return the parent css of @css. This function is guaranteed to return
670 * non-NULL parent as long as @css isn't the root.
673 struct cgroup_subsys_state *css_parent(struct cgroup_subsys_state *css)
679 * task_css_set_check - obtain a task's css_set with extra access conditions
680 * @task: the task to obtain css_set for
681 * @__c: extra condition expression to be passed to rcu_dereference_check()
683 * A task's css_set is RCU protected, initialized and exited while holding
684 * task_lock(), and can only be modified while holding both cgroup_mutex
685 * and task_lock() while the task is alive. This macro verifies that the
686 * caller is inside proper critical section and returns @task's css_set.
688 * The caller can also specify additional allowed conditions via @__c, such
689 * as locks used during the cgroup_subsys::attach() methods.
691 #ifdef CONFIG_PROVE_RCU
692 extern struct mutex cgroup_mutex;
693 #define task_css_set_check(task, __c) \
694 rcu_dereference_check((task)->cgroups, \
695 lockdep_is_held(&(task)->alloc_lock) || \
696 lockdep_is_held(&cgroup_mutex) || (__c))
698 #define task_css_set_check(task, __c) \
699 rcu_dereference((task)->cgroups)
703 * task_css_check - obtain css for (task, subsys) w/ extra access conds
704 * @task: the target task
705 * @subsys_id: the target subsystem ID
706 * @__c: extra condition expression to be passed to rcu_dereference_check()
708 * Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The
709 * synchronization rules are the same as task_css_set_check().
711 #define task_css_check(task, subsys_id, __c) \
712 task_css_set_check((task), (__c))->subsys[(subsys_id)]
715 * task_css_set - obtain a task's css_set
716 * @task: the task to obtain css_set for
718 * See task_css_set_check().
720 static inline struct css_set *task_css_set(struct task_struct *task)
722 return task_css_set_check(task, false);
726 * task_css - obtain css for (task, subsys)
727 * @task: the target task
728 * @subsys_id: the target subsystem ID
730 * See task_css_check().
732 static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
735 return task_css_check(task, subsys_id, false);
738 static inline struct cgroup *task_cgroup(struct task_struct *task,
741 return task_css(task, subsys_id)->cgroup;
744 struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
745 struct cgroup_subsys_state *parent);
747 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
750 * css_for_each_child - iterate through children of a css
751 * @pos: the css * to use as the loop cursor
752 * @parent: css whose children to walk
754 * Walk @parent's children. Must be called under rcu_read_lock(). A child
755 * css which hasn't finished ->css_online() or already has finished
756 * ->css_offline() may show up during traversal and it's each subsystem's
757 * responsibility to verify that each @pos is alive.
759 * If a subsystem synchronizes against the parent in its ->css_online() and
760 * before starting iterating, a css which finished ->css_online() is
761 * guaranteed to be visible in the future iterations.
763 * It is allowed to temporarily drop RCU read lock during iteration. The
764 * caller is responsible for ensuring that @pos remains accessible until
765 * the start of the next iteration by, for example, bumping the css refcnt.
767 #define css_for_each_child(pos, parent) \
768 for ((pos) = css_next_child(NULL, (parent)); (pos); \
769 (pos) = css_next_child((pos), (parent)))
771 struct cgroup_subsys_state *
772 css_next_descendant_pre(struct cgroup_subsys_state *pos,
773 struct cgroup_subsys_state *css);
775 struct cgroup_subsys_state *
776 css_rightmost_descendant(struct cgroup_subsys_state *pos);
779 * css_for_each_descendant_pre - pre-order walk of a css's descendants
780 * @pos: the css * to use as the loop cursor
781 * @root: css whose descendants to walk
783 * Walk @root's descendants. @root is included in the iteration and the
784 * first node to be visited. Must be called under rcu_read_lock(). A
785 * descendant css which hasn't finished ->css_online() or already has
786 * finished ->css_offline() may show up during traversal and it's each
787 * subsystem's responsibility to verify that each @pos is alive.
789 * If a subsystem synchronizes against the parent in its ->css_online() and
790 * before starting iterating, and synchronizes against @pos on each
791 * iteration, any descendant css which finished ->css_online() is
792 * guaranteed to be visible in the future iterations.
794 * In other words, the following guarantees that a descendant can't escape
795 * state updates of its ancestors.
799 * Lock @css's parent and @css;
800 * Inherit state from the parent;
804 * my_update_state(@css)
806 * css_for_each_descendant_pre(@pos, @css) {
809 * Update @css's state;
811 * Verify @pos is alive and inherit state from its parent;
816 * As long as the inheriting step, including checking the parent state, is
817 * enclosed inside @pos locking, double-locking the parent isn't necessary
818 * while inheriting. The state update to the parent is guaranteed to be
819 * visible by walking order and, as long as inheriting operations to the
820 * same @pos are atomic to each other, multiple updates racing each other
821 * still result in the correct state. It's guaranateed that at least one
822 * inheritance happens for any css after the latest update to its parent.
824 * If checking parent's state requires locking the parent, each inheriting
825 * iteration should lock and unlock both @pos->parent and @pos.
827 * Alternatively, a subsystem may choose to use a single global lock to
828 * synchronize ->css_online() and ->css_offline() against tree-walking
831 * It is allowed to temporarily drop RCU read lock during iteration. The
832 * caller is responsible for ensuring that @pos remains accessible until
833 * the start of the next iteration by, for example, bumping the css refcnt.
835 #define css_for_each_descendant_pre(pos, css) \
836 for ((pos) = css_next_descendant_pre(NULL, (css)); (pos); \
837 (pos) = css_next_descendant_pre((pos), (css)))
839 struct cgroup_subsys_state *
840 css_next_descendant_post(struct cgroup_subsys_state *pos,
841 struct cgroup_subsys_state *css);
844 * css_for_each_descendant_post - post-order walk of a css's descendants
845 * @pos: the css * to use as the loop cursor
846 * @css: css whose descendants to walk
848 * Similar to css_for_each_descendant_pre() but performs post-order
849 * traversal instead. @root is included in the iteration and the last
850 * node to be visited. Note that the walk visibility guarantee described
851 * in pre-order walk doesn't apply the same to post-order walks.
853 #define css_for_each_descendant_post(pos, css) \
854 for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \
855 (pos) = css_next_descendant_post((pos), (css)))
857 /* A css_task_iter should be treated as an opaque object */
858 struct css_task_iter {
859 struct cgroup_subsys_state *origin_css;
860 struct list_head *cset_link;
861 struct list_head *task;
864 void css_task_iter_start(struct cgroup_subsys_state *css,
865 struct css_task_iter *it);
866 struct task_struct *css_task_iter_next(struct css_task_iter *it);
867 void css_task_iter_end(struct css_task_iter *it);
869 int css_scan_tasks(struct cgroup_subsys_state *css,
870 bool (*test)(struct task_struct *, void *),
871 void (*process)(struct task_struct *, void *),
872 void *data, struct ptr_heap *heap);
874 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
875 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
878 * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
879 * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
880 * CSS ID is assigned at cgroup allocation (create) automatically
881 * and removed when subsys calls free_css_id() function. This is because
882 * the lifetime of cgroup_subsys_state is subsys's matter.
884 * Looking up and scanning function should be called under rcu_read_lock().
885 * Taking cgroup_mutex is not necessary for following calls.
886 * But the css returned by this routine can be "not populated yet" or "being
887 * destroyed". The caller should check css and cgroup's status.
891 * Typically Called at ->destroy(), or somewhere the subsys frees
892 * cgroup_subsys_state.
894 void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
896 /* Find a cgroup_subsys_state which has given ID */
898 struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id);
900 /* Returns true if root is ancestor of cg */
901 bool css_is_ancestor(struct cgroup_subsys_state *cg,
902 const struct cgroup_subsys_state *root);
904 /* Get id and depth of css */
905 unsigned short css_id(struct cgroup_subsys_state *css);
906 struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id);
908 #else /* !CONFIG_CGROUPS */
910 static inline int cgroup_init_early(void) { return 0; }
911 static inline int cgroup_init(void) { return 0; }
912 static inline void cgroup_fork(struct task_struct *p) {}
913 static inline void cgroup_post_fork(struct task_struct *p) {}
914 static inline void cgroup_exit(struct task_struct *p, int callbacks) {}
916 static inline int cgroupstats_build(struct cgroupstats *stats,
917 struct dentry *dentry)
922 /* No cgroups - nothing to do */
923 static inline int cgroup_attach_task_all(struct task_struct *from,
924 struct task_struct *t)
929 #endif /* !CONFIG_CGROUPS */
931 #endif /* _LINUX_CGROUP_H */