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/rwsem.h>
18 #include <linux/idr.h>
19 #include <linux/workqueue.h>
21 #include <linux/percpu-refcount.h>
22 #include <linux/seq_file.h>
23 #include <linux/kernfs.h>
24 #include <linux/wait.h>
32 extern int cgroup_init_early(void);
33 extern int cgroup_init(void);
34 extern void cgroup_fork(struct task_struct
*p
);
35 extern void cgroup_post_fork(struct task_struct
*p
);
36 extern void cgroup_exit(struct task_struct
*p
);
37 extern int cgroupstats_build(struct cgroupstats
*stats
,
38 struct dentry
*dentry
);
40 extern int proc_cgroup_show(struct seq_file
*m
, struct pid_namespace
*ns
,
41 struct pid
*pid
, struct task_struct
*tsk
);
43 /* define the enumeration of all cgroup subsystems */
44 #define SUBSYS(_x) _x ## _cgrp_id,
45 enum cgroup_subsys_id
{
46 #include <linux/cgroup_subsys.h>
52 * Per-subsystem/per-cgroup state maintained by the system. This is the
53 * fundamental structural building block that controllers deal with.
55 * Fields marked with "PI:" are public and immutable and may be accessed
56 * directly without synchronization.
58 struct cgroup_subsys_state
{
59 /* PI: the cgroup that this css is attached to */
60 struct cgroup
*cgroup
;
62 /* PI: the cgroup subsystem that this css is attached to */
63 struct cgroup_subsys
*ss
;
65 /* reference count - access via css_[try]get() and css_put() */
66 struct percpu_ref refcnt
;
68 /* PI: the parent css */
69 struct cgroup_subsys_state
*parent
;
71 /* siblings list anchored at the parent's ->children */
72 struct list_head sibling
;
73 struct list_head children
;
76 * PI: Subsys-unique ID. 0 is unused and root is always 1. The
77 * matching css can be looked up using css_from_id().
84 * Monotonically increasing unique serial number which defines a
85 * uniform order among all csses. It's guaranteed that all
86 * ->children lists are in the ascending order of ->serial_nr and
87 * used to allow interrupting and resuming iterations.
91 /* percpu_ref killing and RCU release */
92 struct rcu_head rcu_head
;
93 struct work_struct destroy_work
;
96 /* bits in struct cgroup_subsys_state flags field */
98 CSS_NO_REF
= (1 << 0), /* no reference counting for this css */
99 CSS_ONLINE
= (1 << 1), /* between ->css_online() and ->css_offline() */
100 CSS_RELEASED
= (1 << 2), /* refcnt reached zero, released */
104 * css_get - obtain a reference on the specified css
107 * The caller must already have a reference.
109 static inline void css_get(struct cgroup_subsys_state
*css
)
111 if (!(css
->flags
& CSS_NO_REF
))
112 percpu_ref_get(&css
->refcnt
);
116 * css_get_many - obtain references on the specified css
118 * @n: number of references to get
120 * The caller must already have a reference.
122 static inline void css_get_many(struct cgroup_subsys_state
*css
, unsigned int n
)
124 if (!(css
->flags
& CSS_NO_REF
))
125 percpu_ref_get_many(&css
->refcnt
, n
);
129 * css_tryget - try to obtain a reference on the specified css
132 * Obtain a reference on @css unless it already has reached zero and is
133 * being released. This function doesn't care whether @css is on or
134 * offline. The caller naturally needs to ensure that @css is accessible
135 * but doesn't have to be holding a reference on it - IOW, RCU protected
136 * access is good enough for this function. Returns %true if a reference
137 * count was successfully obtained; %false otherwise.
139 static inline bool css_tryget(struct cgroup_subsys_state
*css
)
141 if (!(css
->flags
& CSS_NO_REF
))
142 return percpu_ref_tryget(&css
->refcnt
);
147 * css_tryget_online - try to obtain a reference on the specified css if online
150 * Obtain a reference on @css if it's online. The caller naturally needs
151 * to ensure that @css is accessible but doesn't have to be holding a
152 * reference on it - IOW, RCU protected access is good enough for this
153 * function. Returns %true if a reference count was successfully obtained;
156 static inline bool css_tryget_online(struct cgroup_subsys_state
*css
)
158 if (!(css
->flags
& CSS_NO_REF
))
159 return percpu_ref_tryget_live(&css
->refcnt
);
164 * css_put - put a css reference
167 * Put a reference obtained via css_get() and css_tryget_online().
169 static inline void css_put(struct cgroup_subsys_state
*css
)
171 if (!(css
->flags
& CSS_NO_REF
))
172 percpu_ref_put(&css
->refcnt
);
176 * css_put_many - put css references
178 * @n: number of references to put
180 * Put references obtained via css_get() and css_tryget_online().
182 static inline void css_put_many(struct cgroup_subsys_state
*css
, unsigned int n
)
184 if (!(css
->flags
& CSS_NO_REF
))
185 percpu_ref_put_many(&css
->refcnt
, n
);
188 /* bits in struct cgroup flags field */
190 /* Control Group requires release notifications to userspace */
191 CGRP_NOTIFY_ON_RELEASE
,
193 * Clone the parent's configuration when creating a new child
194 * cpuset cgroup. For historical reasons, this option can be
195 * specified at mount time and thus is implemented here.
197 CGRP_CPUSET_CLONE_CHILDREN
,
201 /* self css with NULL ->ss, points back to this cgroup */
202 struct cgroup_subsys_state self
;
204 unsigned long flags
; /* "unsigned long" so bitops work */
207 * idr allocated in-hierarchy ID.
209 * ID 0 is not used, the ID of the root cgroup is always 1, and a
210 * new cgroup will be assigned with a smallest available ID.
212 * Allocating/Removing ID must be protected by cgroup_mutex.
217 * If this cgroup contains any tasks, it contributes one to
218 * populated_cnt. All children with non-zero popuplated_cnt of
219 * their own contribute one. The count is zero iff there's no task
220 * in this cgroup or its subtree.
224 struct kernfs_node
*kn
; /* cgroup kernfs entry */
225 struct kernfs_node
*populated_kn
; /* kn for "cgroup.subtree_populated" */
228 * The bitmask of subsystems enabled on the child cgroups.
229 * ->subtree_control is the one configured through
230 * "cgroup.subtree_control" while ->child_subsys_mask is the
231 * effective one which may have more subsystems enabled.
232 * Controller knobs are made available iff it's enabled in
235 unsigned int subtree_control
;
236 unsigned int child_subsys_mask
;
238 /* Private pointers for each registered subsystem */
239 struct cgroup_subsys_state __rcu
*subsys
[CGROUP_SUBSYS_COUNT
];
241 struct cgroup_root
*root
;
244 * List of cgrp_cset_links pointing at css_sets with tasks in this
245 * cgroup. Protected by css_set_lock.
247 struct list_head cset_links
;
250 * On the default hierarchy, a css_set for a cgroup with some
251 * susbsys disabled will point to css's which are associated with
252 * the closest ancestor which has the subsys enabled. The
253 * following lists all css_sets which point to this cgroup's css
254 * for the given subsystem.
256 struct list_head e_csets
[CGROUP_SUBSYS_COUNT
];
259 * list of pidlists, up to two for each namespace (one for procs, one
260 * for tasks); created on demand.
262 struct list_head pidlists
;
263 struct mutex pidlist_mutex
;
265 /* used to wait for offlining of csses */
266 wait_queue_head_t offline_waitq
;
268 /* used to schedule release agent */
269 struct work_struct release_agent_work
;
272 #define MAX_CGROUP_ROOT_NAMELEN 64
274 /* cgroup_root->flags */
276 CGRP_ROOT_SANE_BEHAVIOR
= (1 << 0), /* __DEVEL__sane_behavior specified */
277 CGRP_ROOT_NOPREFIX
= (1 << 1), /* mounted subsystems have no named prefix */
278 CGRP_ROOT_XATTR
= (1 << 2), /* supports extended attributes */
282 * A cgroup_root represents the root of a cgroup hierarchy, and may be
283 * associated with a kernfs_root to form an active hierarchy. This is
284 * internal to cgroup core. Don't access directly from controllers.
287 struct kernfs_root
*kf_root
;
289 /* The bitmask of subsystems attached to this hierarchy */
290 unsigned int subsys_mask
;
292 /* Unique id for this hierarchy. */
295 /* The root cgroup. Root is destroyed on its release. */
298 /* Number of cgroups in the hierarchy, used only for /proc/cgroups */
301 /* A list running through the active hierarchies */
302 struct list_head root_list
;
304 /* Hierarchy-specific flags */
307 /* IDs for cgroups in this hierarchy */
308 struct idr cgroup_idr
;
310 /* The path to use for release notifications. */
311 char release_agent_path
[PATH_MAX
];
313 /* The name for this hierarchy - may be empty */
314 char name
[MAX_CGROUP_ROOT_NAMELEN
];
318 * A css_set is a structure holding pointers to a set of
319 * cgroup_subsys_state objects. This saves space in the task struct
320 * object and speeds up fork()/exit(), since a single inc/dec and a
321 * list_add()/del() can bump the reference count on the entire cgroup
327 /* Reference count */
331 * List running through all cgroup groups in the same hash
332 * slot. Protected by css_set_lock
334 struct hlist_node hlist
;
337 * Lists running through all tasks using this cgroup group.
338 * mg_tasks lists tasks which belong to this cset but are in the
339 * process of being migrated out or in. Protected by
340 * css_set_rwsem, but, during migration, once tasks are moved to
341 * mg_tasks, it can be read safely while holding cgroup_mutex.
343 struct list_head tasks
;
344 struct list_head mg_tasks
;
347 * List of cgrp_cset_links pointing at cgroups referenced from this
348 * css_set. Protected by css_set_lock.
350 struct list_head cgrp_links
;
352 /* the default cgroup associated with this css_set */
353 struct cgroup
*dfl_cgrp
;
356 * Set of subsystem states, one for each subsystem. This array is
357 * immutable after creation apart from the init_css_set during
358 * subsystem registration (at boot time).
360 struct cgroup_subsys_state
*subsys
[CGROUP_SUBSYS_COUNT
];
363 * List of csets participating in the on-going migration either as
364 * source or destination. Protected by cgroup_mutex.
366 struct list_head mg_preload_node
;
367 struct list_head mg_node
;
370 * If this cset is acting as the source of migration the following
371 * two fields are set. mg_src_cgrp is the source cgroup of the
372 * on-going migration and mg_dst_cset is the destination cset the
373 * target tasks on this cset should be migrated to. Protected by
376 struct cgroup
*mg_src_cgrp
;
377 struct css_set
*mg_dst_cset
;
380 * On the default hierarhcy, ->subsys[ssid] may point to a css
381 * attached to an ancestor instead of the cgroup this css_set is
382 * associated with. The following node is anchored at
383 * ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to
384 * iterate through all css's attached to a given cgroup.
386 struct list_head e_cset_node
[CGROUP_SUBSYS_COUNT
];
388 /* For RCU-protected deletion */
389 struct rcu_head rcu_head
;
393 * struct cftype: handler definitions for cgroup control files
395 * When reading/writing to a file:
396 * - the cgroup to use is file->f_path.dentry->d_parent->d_fsdata
397 * - the 'cftype' of the file is file->f_path.dentry->d_fsdata
402 CFTYPE_ONLY_ON_ROOT
= (1 << 0), /* only create on root cgrp */
403 CFTYPE_NOT_ON_ROOT
= (1 << 1), /* don't create on root cgrp */
404 CFTYPE_NO_PREFIX
= (1 << 3), /* (DON'T USE FOR NEW FILES) no subsys prefix */
406 /* internal flags, do not use outside cgroup core proper */
407 __CFTYPE_ONLY_ON_DFL
= (1 << 16), /* only on default hierarchy */
408 __CFTYPE_NOT_ON_DFL
= (1 << 17), /* not on default hierarchy */
411 #define MAX_CFTYPE_NAME 64
415 * By convention, the name should begin with the name of the
416 * subsystem, followed by a period. Zero length string indicates
417 * end of cftype array.
419 char name
[MAX_CFTYPE_NAME
];
422 * If not 0, file mode is set to this value, otherwise it will
423 * be figured out automatically
428 * The maximum length of string, excluding trailing nul, that can
429 * be passed to write. If < PAGE_SIZE-1, PAGE_SIZE-1 is assumed.
431 size_t max_write_len
;
437 * Fields used for internal bookkeeping. Initialized automatically
438 * during registration.
440 struct cgroup_subsys
*ss
; /* NULL for cgroup core files */
441 struct list_head node
; /* anchored at ss->cfts */
442 struct kernfs_ops
*kf_ops
;
445 * read_u64() is a shortcut for the common case of returning a
446 * single integer. Use it in place of read()
448 u64 (*read_u64
)(struct cgroup_subsys_state
*css
, struct cftype
*cft
);
450 * read_s64() is a signed version of read_u64()
452 s64 (*read_s64
)(struct cgroup_subsys_state
*css
, struct cftype
*cft
);
454 /* generic seq_file read interface */
455 int (*seq_show
)(struct seq_file
*sf
, void *v
);
457 /* optional ops, implement all or none */
458 void *(*seq_start
)(struct seq_file
*sf
, loff_t
*ppos
);
459 void *(*seq_next
)(struct seq_file
*sf
, void *v
, loff_t
*ppos
);
460 void (*seq_stop
)(struct seq_file
*sf
, void *v
);
463 * write_u64() is a shortcut for the common case of accepting
464 * a single integer (as parsed by simple_strtoull) from
465 * userspace. Use in place of write(); return 0 or error.
467 int (*write_u64
)(struct cgroup_subsys_state
*css
, struct cftype
*cft
,
470 * write_s64() is a signed version of write_u64()
472 int (*write_s64
)(struct cgroup_subsys_state
*css
, struct cftype
*cft
,
476 * write() is the generic write callback which maps directly to
477 * kernfs write operation and overrides all other operations.
478 * Maximum write size is determined by ->max_write_len. Use
479 * of_css/cft() to access the associated css and cft.
481 ssize_t (*write
)(struct kernfs_open_file
*of
,
482 char *buf
, size_t nbytes
, loff_t off
);
484 #ifdef CONFIG_DEBUG_LOCK_ALLOC
485 struct lock_class_key lockdep_key
;
489 extern struct cgroup_root cgrp_dfl_root
;
490 extern struct css_set init_css_set
;
493 * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
494 * @cgrp: the cgroup of interest
496 * The default hierarchy is the v2 interface of cgroup and this function
497 * can be used to test whether a cgroup is on the default hierarchy for
498 * cases where a subsystem should behave differnetly depending on the
501 * The set of behaviors which change on the default hierarchy are still
502 * being determined and the mount option is prefixed with __DEVEL__.
504 * List of changed behaviors:
506 * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
507 * and "name" are disallowed.
509 * - When mounting an existing superblock, mount options should match.
511 * - Remount is disallowed.
513 * - rename(2) is disallowed.
515 * - "tasks" is removed. Everything should be at process granularity. Use
516 * "cgroup.procs" instead.
518 * - "cgroup.procs" is not sorted. pids will be unique unless they got
519 * recycled inbetween reads.
521 * - "release_agent" and "notify_on_release" are removed. Replacement
522 * notification mechanism will be implemented.
524 * - "cgroup.clone_children" is removed.
526 * - "cgroup.subtree_populated" is available. Its value is 0 if the cgroup
527 * and its descendants contain no task; otherwise, 1. The file also
528 * generates kernfs notification which can be monitored through poll and
529 * [di]notify when the value of the file changes.
531 * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
532 * take masks of ancestors with non-empty cpus/mems, instead of being
533 * moved to an ancestor.
535 * - cpuset: a task can be moved into an empty cpuset, and again it takes
536 * masks of ancestors.
538 * - memcg: use_hierarchy is on by default and the cgroup file for the flag
541 * - blkcg: blk-throttle becomes properly hierarchical.
543 * - debug: disallowed on the default hierarchy.
545 static inline bool cgroup_on_dfl(const struct cgroup
*cgrp
)
547 return cgrp
->root
== &cgrp_dfl_root
;
550 /* no synchronization, the result can only be used as a hint */
551 static inline bool cgroup_has_tasks(struct cgroup
*cgrp
)
553 return !list_empty(&cgrp
->cset_links
);
556 /* returns ino associated with a cgroup */
557 static inline ino_t
cgroup_ino(struct cgroup
*cgrp
)
559 return cgrp
->kn
->ino
;
562 /* cft/css accessors for cftype->write() operation */
563 static inline struct cftype
*of_cft(struct kernfs_open_file
*of
)
568 struct cgroup_subsys_state
*of_css(struct kernfs_open_file
*of
);
570 /* cft/css accessors for cftype->seq_*() operations */
571 static inline struct cftype
*seq_cft(struct seq_file
*seq
)
573 return of_cft(seq
->private);
576 static inline struct cgroup_subsys_state
*seq_css(struct seq_file
*seq
)
578 return of_css(seq
->private);
582 * Name / path handling functions. All are thin wrappers around the kernfs
583 * counterparts and can be called under any context.
586 static inline int cgroup_name(struct cgroup
*cgrp
, char *buf
, size_t buflen
)
588 return kernfs_name(cgrp
->kn
, buf
, buflen
);
591 static inline char * __must_check
cgroup_path(struct cgroup
*cgrp
, char *buf
,
594 return kernfs_path(cgrp
->kn
, buf
, buflen
);
597 static inline void pr_cont_cgroup_name(struct cgroup
*cgrp
)
599 pr_cont_kernfs_name(cgrp
->kn
);
602 static inline void pr_cont_cgroup_path(struct cgroup
*cgrp
)
604 pr_cont_kernfs_path(cgrp
->kn
);
607 char *task_cgroup_path(struct task_struct
*task
, char *buf
, size_t buflen
);
609 int cgroup_add_dfl_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
);
610 int cgroup_add_legacy_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
);
611 int cgroup_rm_cftypes(struct cftype
*cfts
);
613 bool cgroup_is_descendant(struct cgroup
*cgrp
, struct cgroup
*ancestor
);
616 * Control Group taskset, used to pass around set of tasks to cgroup_subsys
619 struct cgroup_taskset
;
620 struct task_struct
*cgroup_taskset_first(struct cgroup_taskset
*tset
);
621 struct task_struct
*cgroup_taskset_next(struct cgroup_taskset
*tset
);
624 * cgroup_taskset_for_each - iterate cgroup_taskset
625 * @task: the loop cursor
626 * @tset: taskset to iterate
628 #define cgroup_taskset_for_each(task, tset) \
629 for ((task) = cgroup_taskset_first((tset)); (task); \
630 (task) = cgroup_taskset_next((tset)))
633 * Control Group subsystem type.
634 * See Documentation/cgroups/cgroups.txt for details
637 struct cgroup_subsys
{
638 struct cgroup_subsys_state
*(*css_alloc
)(struct cgroup_subsys_state
*parent_css
);
639 int (*css_online
)(struct cgroup_subsys_state
*css
);
640 void (*css_offline
)(struct cgroup_subsys_state
*css
);
641 void (*css_released
)(struct cgroup_subsys_state
*css
);
642 void (*css_free
)(struct cgroup_subsys_state
*css
);
643 void (*css_reset
)(struct cgroup_subsys_state
*css
);
644 void (*css_e_css_changed
)(struct cgroup_subsys_state
*css
);
646 int (*can_attach
)(struct cgroup_subsys_state
*css
,
647 struct cgroup_taskset
*tset
);
648 void (*cancel_attach
)(struct cgroup_subsys_state
*css
,
649 struct cgroup_taskset
*tset
);
650 void (*attach
)(struct cgroup_subsys_state
*css
,
651 struct cgroup_taskset
*tset
);
652 void (*fork
)(struct task_struct
*task
);
653 void (*exit
)(struct cgroup_subsys_state
*css
,
654 struct cgroup_subsys_state
*old_css
,
655 struct task_struct
*task
);
656 void (*bind
)(struct cgroup_subsys_state
*root_css
);
662 * If %false, this subsystem is properly hierarchical -
663 * configuration, resource accounting and restriction on a parent
664 * cgroup cover those of its children. If %true, hierarchy support
665 * is broken in some ways - some subsystems ignore hierarchy
666 * completely while others are only implemented half-way.
668 * It's now disallowed to create nested cgroups if the subsystem is
669 * broken and cgroup core will emit a warning message on such
670 * cases. Eventually, all subsystems will be made properly
671 * hierarchical and this will go away.
673 bool broken_hierarchy
;
674 bool warned_broken_hierarchy
;
676 /* the following two fields are initialized automtically during boot */
678 #define MAX_CGROUP_TYPE_NAMELEN 32
681 /* link to parent, protected by cgroup_lock() */
682 struct cgroup_root
*root
;
684 /* idr for css->id */
688 * List of cftypes. Each entry is the first entry of an array
689 * terminated by zero length name.
691 struct list_head cfts
;
694 * Base cftypes which are automatically registered. The two can
695 * point to the same array.
697 struct cftype
*dfl_cftypes
; /* for the default hierarchy */
698 struct cftype
*legacy_cftypes
; /* for the legacy hierarchies */
701 * A subsystem may depend on other subsystems. When such subsystem
702 * is enabled on a cgroup, the depended-upon subsystems are enabled
703 * together if available. Subsystems enabled due to dependency are
704 * not visible to userland until explicitly enabled. The following
705 * specifies the mask of subsystems that this one depends on.
707 unsigned int depends_on
;
710 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
711 #include <linux/cgroup_subsys.h>
715 * task_css_set_check - obtain a task's css_set with extra access conditions
716 * @task: the task to obtain css_set for
717 * @__c: extra condition expression to be passed to rcu_dereference_check()
719 * A task's css_set is RCU protected, initialized and exited while holding
720 * task_lock(), and can only be modified while holding both cgroup_mutex
721 * and task_lock() while the task is alive. This macro verifies that the
722 * caller is inside proper critical section and returns @task's css_set.
724 * The caller can also specify additional allowed conditions via @__c, such
725 * as locks used during the cgroup_subsys::attach() methods.
727 #ifdef CONFIG_PROVE_RCU
728 extern struct mutex cgroup_mutex
;
729 extern struct rw_semaphore css_set_rwsem
;
730 #define task_css_set_check(task, __c) \
731 rcu_dereference_check((task)->cgroups, \
732 lockdep_is_held(&cgroup_mutex) || \
733 lockdep_is_held(&css_set_rwsem) || \
734 ((task)->flags & PF_EXITING) || (__c))
736 #define task_css_set_check(task, __c) \
737 rcu_dereference((task)->cgroups)
741 * task_css_check - obtain css for (task, subsys) w/ extra access conds
742 * @task: the target task
743 * @subsys_id: the target subsystem ID
744 * @__c: extra condition expression to be passed to rcu_dereference_check()
746 * Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The
747 * synchronization rules are the same as task_css_set_check().
749 #define task_css_check(task, subsys_id, __c) \
750 task_css_set_check((task), (__c))->subsys[(subsys_id)]
753 * task_css_set - obtain a task's css_set
754 * @task: the task to obtain css_set for
756 * See task_css_set_check().
758 static inline struct css_set
*task_css_set(struct task_struct
*task
)
760 return task_css_set_check(task
, false);
764 * task_css - obtain css for (task, subsys)
765 * @task: the target task
766 * @subsys_id: the target subsystem ID
768 * See task_css_check().
770 static inline struct cgroup_subsys_state
*task_css(struct task_struct
*task
,
773 return task_css_check(task
, subsys_id
, false);
777 * task_css_is_root - test whether a task belongs to the root css
778 * @task: the target task
779 * @subsys_id: the target subsystem ID
781 * Test whether @task belongs to the root css on the specified subsystem.
782 * May be invoked in any context.
784 static inline bool task_css_is_root(struct task_struct
*task
, int subsys_id
)
786 return task_css_check(task
, subsys_id
, true) ==
787 init_css_set
.subsys
[subsys_id
];
790 static inline struct cgroup
*task_cgroup(struct task_struct
*task
,
793 return task_css(task
, subsys_id
)->cgroup
;
796 struct cgroup_subsys_state
*css_next_child(struct cgroup_subsys_state
*pos
,
797 struct cgroup_subsys_state
*parent
);
799 struct cgroup_subsys_state
*css_from_id(int id
, struct cgroup_subsys
*ss
);
802 * css_for_each_child - iterate through children of a css
803 * @pos: the css * to use as the loop cursor
804 * @parent: css whose children to walk
806 * Walk @parent's children. Must be called under rcu_read_lock().
808 * If a subsystem synchronizes ->css_online() and the start of iteration, a
809 * css which finished ->css_online() is guaranteed to be visible in the
810 * future iterations and will stay visible until the last reference is put.
811 * A css which hasn't finished ->css_online() or already finished
812 * ->css_offline() may show up during traversal. It's each subsystem's
813 * responsibility to synchronize against on/offlining.
815 * It is allowed to temporarily drop RCU read lock during iteration. The
816 * caller is responsible for ensuring that @pos remains accessible until
817 * the start of the next iteration by, for example, bumping the css refcnt.
819 #define css_for_each_child(pos, parent) \
820 for ((pos) = css_next_child(NULL, (parent)); (pos); \
821 (pos) = css_next_child((pos), (parent)))
823 struct cgroup_subsys_state
*
824 css_next_descendant_pre(struct cgroup_subsys_state
*pos
,
825 struct cgroup_subsys_state
*css
);
827 struct cgroup_subsys_state
*
828 css_rightmost_descendant(struct cgroup_subsys_state
*pos
);
831 * css_for_each_descendant_pre - pre-order walk of a css's descendants
832 * @pos: the css * to use as the loop cursor
833 * @root: css whose descendants to walk
835 * Walk @root's descendants. @root is included in the iteration and the
836 * first node to be visited. Must be called under rcu_read_lock().
838 * If a subsystem synchronizes ->css_online() and the start of iteration, a
839 * css which finished ->css_online() is guaranteed to be visible in the
840 * future iterations and will stay visible until the last reference is put.
841 * A css which hasn't finished ->css_online() or already finished
842 * ->css_offline() may show up during traversal. It's each subsystem's
843 * responsibility to synchronize against on/offlining.
845 * For example, the following guarantees that a descendant can't escape
846 * state updates of its ancestors.
850 * Lock @css's parent and @css;
851 * Inherit state from the parent;
855 * my_update_state(@css)
857 * css_for_each_descendant_pre(@pos, @css) {
860 * Update @css's state;
862 * Verify @pos is alive and inherit state from its parent;
867 * As long as the inheriting step, including checking the parent state, is
868 * enclosed inside @pos locking, double-locking the parent isn't necessary
869 * while inheriting. The state update to the parent is guaranteed to be
870 * visible by walking order and, as long as inheriting operations to the
871 * same @pos are atomic to each other, multiple updates racing each other
872 * still result in the correct state. It's guaranateed that at least one
873 * inheritance happens for any css after the latest update to its parent.
875 * If checking parent's state requires locking the parent, each inheriting
876 * iteration should lock and unlock both @pos->parent and @pos.
878 * Alternatively, a subsystem may choose to use a single global lock to
879 * synchronize ->css_online() and ->css_offline() against tree-walking
882 * It is allowed to temporarily drop RCU read lock during iteration. The
883 * caller is responsible for ensuring that @pos remains accessible until
884 * the start of the next iteration by, for example, bumping the css refcnt.
886 #define css_for_each_descendant_pre(pos, css) \
887 for ((pos) = css_next_descendant_pre(NULL, (css)); (pos); \
888 (pos) = css_next_descendant_pre((pos), (css)))
890 struct cgroup_subsys_state
*
891 css_next_descendant_post(struct cgroup_subsys_state
*pos
,
892 struct cgroup_subsys_state
*css
);
895 * css_for_each_descendant_post - post-order walk of a css's descendants
896 * @pos: the css * to use as the loop cursor
897 * @css: css whose descendants to walk
899 * Similar to css_for_each_descendant_pre() but performs post-order
900 * traversal instead. @root is included in the iteration and the last
901 * node to be visited.
903 * If a subsystem synchronizes ->css_online() and the start of iteration, a
904 * css which finished ->css_online() is guaranteed to be visible in the
905 * future iterations and will stay visible until the last reference is put.
906 * A css which hasn't finished ->css_online() or already finished
907 * ->css_offline() may show up during traversal. It's each subsystem's
908 * responsibility to synchronize against on/offlining.
910 * Note that the walk visibility guarantee example described in pre-order
911 * walk doesn't apply the same to post-order walks.
913 #define css_for_each_descendant_post(pos, css) \
914 for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \
915 (pos) = css_next_descendant_post((pos), (css)))
917 bool css_has_online_children(struct cgroup_subsys_state
*css
);
919 /* A css_task_iter should be treated as an opaque object */
920 struct css_task_iter
{
921 struct cgroup_subsys
*ss
;
923 struct list_head
*cset_pos
;
924 struct list_head
*cset_head
;
926 struct list_head
*task_pos
;
927 struct list_head
*tasks_head
;
928 struct list_head
*mg_tasks_head
;
931 void css_task_iter_start(struct cgroup_subsys_state
*css
,
932 struct css_task_iter
*it
);
933 struct task_struct
*css_task_iter_next(struct css_task_iter
*it
);
934 void css_task_iter_end(struct css_task_iter
*it
);
936 int cgroup_attach_task_all(struct task_struct
*from
, struct task_struct
*);
937 int cgroup_transfer_tasks(struct cgroup
*to
, struct cgroup
*from
);
939 struct cgroup_subsys_state
*cgroup_get_e_css(struct cgroup
*cgroup
,
940 struct cgroup_subsys
*ss
);
941 struct cgroup_subsys_state
*css_tryget_online_from_dir(struct dentry
*dentry
,
942 struct cgroup_subsys
*ss
);
944 #else /* !CONFIG_CGROUPS */
946 struct cgroup_subsys_state
;
948 static inline int cgroup_init_early(void) { return 0; }
949 static inline int cgroup_init(void) { return 0; }
950 static inline void cgroup_fork(struct task_struct
*p
) {}
951 static inline void cgroup_post_fork(struct task_struct
*p
) {}
952 static inline void cgroup_exit(struct task_struct
*p
) {}
954 static inline int cgroupstats_build(struct cgroupstats
*stats
,
955 struct dentry
*dentry
)
960 static inline void css_put(struct cgroup_subsys_state
*css
) {}
962 /* No cgroups - nothing to do */
963 static inline int cgroup_attach_task_all(struct task_struct
*from
,
964 struct task_struct
*t
)
969 #endif /* !CONFIG_CGROUPS */
971 #endif /* _LINUX_CGROUP_H */