2 * linux/cgroup-defs.h - basic definitions for cgroup
4 * This file provides basic type and interface. Include this file directly
5 * only if necessary to avoid cyclic dependencies.
7 #ifndef _LINUX_CGROUP_DEFS_H
8 #define _LINUX_CGROUP_DEFS_H
10 #include <linux/limits.h>
11 #include <linux/list.h>
12 #include <linux/idr.h>
13 #include <linux/wait.h>
14 #include <linux/mutex.h>
15 #include <linux/rcupdate.h>
16 #include <linux/percpu-refcount.h>
17 #include <linux/percpu-rwsem.h>
18 #include <linux/workqueue.h>
25 struct cgroup_taskset;
28 struct kernfs_open_file;
31 #define MAX_CGROUP_TYPE_NAMELEN 32
32 #define MAX_CGROUP_ROOT_NAMELEN 64
33 #define MAX_CFTYPE_NAME 64
35 /* define the enumeration of all cgroup subsystems */
36 #define SUBSYS(_x) _x ## _cgrp_id,
37 enum cgroup_subsys_id {
38 #include <linux/cgroup_subsys.h>
43 /* bits in struct cgroup_subsys_state flags field */
45 CSS_NO_REF = (1 << 0), /* no reference counting for this css */
46 CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */
47 CSS_RELEASED = (1 << 2), /* refcnt reached zero, released */
50 /* bits in struct cgroup flags field */
52 /* Control Group requires release notifications to userspace */
53 CGRP_NOTIFY_ON_RELEASE,
55 * Clone the parent's configuration when creating a new child
56 * cpuset cgroup. For historical reasons, this option can be
57 * specified at mount time and thus is implemented here.
59 CGRP_CPUSET_CLONE_CHILDREN,
62 /* cgroup_root->flags */
64 CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
65 CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
70 CFTYPE_ONLY_ON_ROOT = (1 << 0), /* only create on root cgrp */
71 CFTYPE_NOT_ON_ROOT = (1 << 1), /* don't create on root cgrp */
72 CFTYPE_NO_PREFIX = (1 << 3), /* (DON'T USE FOR NEW FILES) no subsys prefix */
73 CFTYPE_WORLD_WRITABLE = (1 << 4), /* (DON'T USE FOR NEW FILES) S_IWUGO */
75 /* internal flags, do not use outside cgroup core proper */
76 __CFTYPE_ONLY_ON_DFL = (1 << 16), /* only on default hierarchy */
77 __CFTYPE_NOT_ON_DFL = (1 << 17), /* not on default hierarchy */
81 * cgroup_file is the handle for a file instance created in a cgroup which
82 * is used, for example, to generate file changed notifications. This can
83 * be obtained by setting cftype->file_offset.
86 /* do not access any fields from outside cgroup core */
87 struct kernfs_node *kn;
91 * Per-subsystem/per-cgroup state maintained by the system. This is the
92 * fundamental structural building block that controllers deal with.
94 * Fields marked with "PI:" are public and immutable and may be accessed
95 * directly without synchronization.
97 struct cgroup_subsys_state {
98 /* PI: the cgroup that this css is attached to */
99 struct cgroup *cgroup;
101 /* PI: the cgroup subsystem that this css is attached to */
102 struct cgroup_subsys *ss;
104 /* reference count - access via css_[try]get() and css_put() */
105 struct percpu_ref refcnt;
107 /* PI: the parent css */
108 struct cgroup_subsys_state *parent;
110 /* siblings list anchored at the parent's ->children */
111 struct list_head sibling;
112 struct list_head children;
115 * PI: Subsys-unique ID. 0 is unused and root is always 1. The
116 * matching css can be looked up using css_from_id().
123 * Monotonically increasing unique serial number which defines a
124 * uniform order among all csses. It's guaranteed that all
125 * ->children lists are in the ascending order of ->serial_nr and
126 * used to allow interrupting and resuming iterations.
131 * Incremented by online self and children. Used to guarantee that
132 * parents are not offlined before their children.
136 /* percpu_ref killing and RCU release */
137 struct rcu_head rcu_head;
138 struct work_struct destroy_work;
142 * A css_set is a structure holding pointers to a set of
143 * cgroup_subsys_state objects. This saves space in the task struct
144 * object and speeds up fork()/exit(), since a single inc/dec and a
145 * list_add()/del() can bump the reference count on the entire cgroup
149 /* Reference count */
153 * List running through all cgroup groups in the same hash
154 * slot. Protected by css_set_lock
156 struct hlist_node hlist;
159 * Lists running through all tasks using this cgroup group.
160 * mg_tasks lists tasks which belong to this cset but are in the
161 * process of being migrated out or in. Protected by
162 * css_set_rwsem, but, during migration, once tasks are moved to
163 * mg_tasks, it can be read safely while holding cgroup_mutex.
165 struct list_head tasks;
166 struct list_head mg_tasks;
169 * List of cgrp_cset_links pointing at cgroups referenced from this
170 * css_set. Protected by css_set_lock.
172 struct list_head cgrp_links;
174 /* the default cgroup associated with this css_set */
175 struct cgroup *dfl_cgrp;
178 * Set of subsystem states, one for each subsystem. This array is
179 * immutable after creation apart from the init_css_set during
180 * subsystem registration (at boot time).
182 struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
185 * List of csets participating in the on-going migration either as
186 * source or destination. Protected by cgroup_mutex.
188 struct list_head mg_preload_node;
189 struct list_head mg_node;
192 * If this cset is acting as the source of migration the following
193 * two fields are set. mg_src_cgrp is the source cgroup of the
194 * on-going migration and mg_dst_cset is the destination cset the
195 * target tasks on this cset should be migrated to. Protected by
198 struct cgroup *mg_src_cgrp;
199 struct css_set *mg_dst_cset;
202 * On the default hierarhcy, ->subsys[ssid] may point to a css
203 * attached to an ancestor instead of the cgroup this css_set is
204 * associated with. The following node is anchored at
205 * ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to
206 * iterate through all css's attached to a given cgroup.
208 struct list_head e_cset_node[CGROUP_SUBSYS_COUNT];
210 /* all css_task_iters currently walking this cset */
211 struct list_head task_iters;
213 /* For RCU-protected deletion */
214 struct rcu_head rcu_head;
218 /* self css with NULL ->ss, points back to this cgroup */
219 struct cgroup_subsys_state self;
221 unsigned long flags; /* "unsigned long" so bitops work */
224 * idr allocated in-hierarchy ID.
226 * ID 0 is not used, the ID of the root cgroup is always 1, and a
227 * new cgroup will be assigned with a smallest available ID.
229 * Allocating/Removing ID must be protected by cgroup_mutex.
234 * The depth this cgroup is at. The root is at depth zero and each
235 * step down the hierarchy increments the level. This along with
236 * ancestor_ids[] can determine whether a given cgroup is a
237 * descendant of another without traversing the hierarchy.
242 * Each non-empty css_set associated with this cgroup contributes
243 * one to populated_cnt. All children with non-zero popuplated_cnt
244 * of their own contribute one. The count is zero iff there's no
245 * task in this cgroup or its subtree.
249 struct kernfs_node *kn; /* cgroup kernfs entry */
250 struct cgroup_file procs_file; /* handle for "cgroup.procs" */
251 struct cgroup_file events_file; /* handle for "cgroup.events" */
254 * The bitmask of subsystems enabled on the child cgroups.
255 * ->subtree_control is the one configured through
256 * "cgroup.subtree_control" while ->child_subsys_mask is the
257 * effective one which may have more subsystems enabled.
258 * Controller knobs are made available iff it's enabled in
261 unsigned int subtree_control;
262 unsigned int child_subsys_mask;
264 /* Private pointers for each registered subsystem */
265 struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
267 struct cgroup_root *root;
270 * List of cgrp_cset_links pointing at css_sets with tasks in this
271 * cgroup. Protected by css_set_lock.
273 struct list_head cset_links;
276 * On the default hierarchy, a css_set for a cgroup with some
277 * susbsys disabled will point to css's which are associated with
278 * the closest ancestor which has the subsys enabled. The
279 * following lists all css_sets which point to this cgroup's css
280 * for the given subsystem.
282 struct list_head e_csets[CGROUP_SUBSYS_COUNT];
285 * list of pidlists, up to two for each namespace (one for procs, one
286 * for tasks); created on demand.
288 struct list_head pidlists;
289 struct mutex pidlist_mutex;
291 /* used to wait for offlining of csses */
292 wait_queue_head_t offline_waitq;
294 /* used to schedule release agent */
295 struct work_struct release_agent_work;
297 /* ids of the ancestors at each level including self */
302 * A cgroup_root represents the root of a cgroup hierarchy, and may be
303 * associated with a kernfs_root to form an active hierarchy. This is
304 * internal to cgroup core. Don't access directly from controllers.
307 struct kernfs_root *kf_root;
309 /* The bitmask of subsystems attached to this hierarchy */
310 unsigned int subsys_mask;
312 /* Unique id for this hierarchy. */
315 /* The root cgroup. Root is destroyed on its release. */
318 /* for cgrp->ancestor_ids[0] */
319 int cgrp_ancestor_id_storage;
321 /* Number of cgroups in the hierarchy, used only for /proc/cgroups */
324 /* A list running through the active hierarchies */
325 struct list_head root_list;
327 /* Hierarchy-specific flags */
330 /* IDs for cgroups in this hierarchy */
331 struct idr cgroup_idr;
333 /* The path to use for release notifications. */
334 char release_agent_path[PATH_MAX];
336 /* The name for this hierarchy - may be empty */
337 char name[MAX_CGROUP_ROOT_NAMELEN];
341 * struct cftype: handler definitions for cgroup control files
343 * When reading/writing to a file:
344 * - the cgroup to use is file->f_path.dentry->d_parent->d_fsdata
345 * - the 'cftype' of the file is file->f_path.dentry->d_fsdata
349 * By convention, the name should begin with the name of the
350 * subsystem, followed by a period. Zero length string indicates
351 * end of cftype array.
353 char name[MAX_CFTYPE_NAME];
354 unsigned long private;
357 * The maximum length of string, excluding trailing nul, that can
358 * be passed to write. If < PAGE_SIZE-1, PAGE_SIZE-1 is assumed.
360 size_t max_write_len;
366 * If non-zero, should contain the offset from the start of css to
367 * a struct cgroup_file field. cgroup will record the handle of
368 * the created file into it. The recorded handle can be used as
369 * long as the containing css remains accessible.
371 unsigned int file_offset;
374 * Fields used for internal bookkeeping. Initialized automatically
375 * during registration.
377 struct cgroup_subsys *ss; /* NULL for cgroup core files */
378 struct list_head node; /* anchored at ss->cfts */
379 struct kernfs_ops *kf_ops;
382 * read_u64() is a shortcut for the common case of returning a
383 * single integer. Use it in place of read()
385 u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft);
387 * read_s64() is a signed version of read_u64()
389 s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft);
391 /* generic seq_file read interface */
392 int (*seq_show)(struct seq_file *sf, void *v);
394 /* optional ops, implement all or none */
395 void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
396 void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
397 void (*seq_stop)(struct seq_file *sf, void *v);
400 * write_u64() is a shortcut for the common case of accepting
401 * a single integer (as parsed by simple_strtoull) from
402 * userspace. Use in place of write(); return 0 or error.
404 int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft,
407 * write_s64() is a signed version of write_u64()
409 int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft,
413 * write() is the generic write callback which maps directly to
414 * kernfs write operation and overrides all other operations.
415 * Maximum write size is determined by ->max_write_len. Use
416 * of_css/cft() to access the associated css and cft.
418 ssize_t (*write)(struct kernfs_open_file *of,
419 char *buf, size_t nbytes, loff_t off);
421 #ifdef CONFIG_DEBUG_LOCK_ALLOC
422 struct lock_class_key lockdep_key;
427 * Control Group subsystem type.
428 * See Documentation/cgroups/cgroups.txt for details
430 struct cgroup_subsys {
431 struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);
432 int (*css_online)(struct cgroup_subsys_state *css);
433 void (*css_offline)(struct cgroup_subsys_state *css);
434 void (*css_released)(struct cgroup_subsys_state *css);
435 void (*css_free)(struct cgroup_subsys_state *css);
436 void (*css_reset)(struct cgroup_subsys_state *css);
437 void (*css_e_css_changed)(struct cgroup_subsys_state *css);
439 int (*can_attach)(struct cgroup_taskset *tset);
440 void (*cancel_attach)(struct cgroup_taskset *tset);
441 void (*attach)(struct cgroup_taskset *tset);
442 int (*can_fork)(struct task_struct *task);
443 void (*cancel_fork)(struct task_struct *task);
444 void (*fork)(struct task_struct *task);
445 void (*exit)(struct task_struct *task);
446 void (*free)(struct task_struct *task);
447 void (*bind)(struct cgroup_subsys_state *root_css);
452 * If %false, this subsystem is properly hierarchical -
453 * configuration, resource accounting and restriction on a parent
454 * cgroup cover those of its children. If %true, hierarchy support
455 * is broken in some ways - some subsystems ignore hierarchy
456 * completely while others are only implemented half-way.
458 * It's now disallowed to create nested cgroups if the subsystem is
459 * broken and cgroup core will emit a warning message on such
460 * cases. Eventually, all subsystems will be made properly
461 * hierarchical and this will go away.
463 bool broken_hierarchy;
464 bool warned_broken_hierarchy;
466 /* the following two fields are initialized automtically during boot */
470 /* optional, initialized automatically during boot if not set */
471 const char *legacy_name;
473 /* link to parent, protected by cgroup_lock() */
474 struct cgroup_root *root;
476 /* idr for css->id */
480 * List of cftypes. Each entry is the first entry of an array
481 * terminated by zero length name.
483 struct list_head cfts;
486 * Base cftypes which are automatically registered. The two can
487 * point to the same array.
489 struct cftype *dfl_cftypes; /* for the default hierarchy */
490 struct cftype *legacy_cftypes; /* for the legacy hierarchies */
493 * A subsystem may depend on other subsystems. When such subsystem
494 * is enabled on a cgroup, the depended-upon subsystems are enabled
495 * together if available. Subsystems enabled due to dependency are
496 * not visible to userland until explicitly enabled. The following
497 * specifies the mask of subsystems that this one depends on.
499 unsigned int depends_on;
502 extern struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
505 * cgroup_threadgroup_change_begin - threadgroup exclusion for cgroups
508 * Called from threadgroup_change_begin() and allows cgroup operations to
509 * synchronize against threadgroup changes using a percpu_rw_semaphore.
511 static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk)
513 percpu_down_read(&cgroup_threadgroup_rwsem);
517 * cgroup_threadgroup_change_end - threadgroup exclusion for cgroups
520 * Called from threadgroup_change_end(). Counterpart of
521 * cgroup_threadcgroup_change_begin().
523 static inline void cgroup_threadgroup_change_end(struct task_struct *tsk)
525 percpu_up_read(&cgroup_threadgroup_rwsem);
528 #else /* CONFIG_CGROUPS */
530 #define CGROUP_SUBSYS_COUNT 0
532 static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk) {}
533 static inline void cgroup_threadgroup_change_end(struct task_struct *tsk) {}
535 #endif /* CONFIG_CGROUPS */
537 #ifdef CONFIG_SOCK_CGROUP_DATA
540 * sock_cgroup_data is embedded at sock->sk_cgrp_data and contains
541 * per-socket cgroup information except for memcg association.
543 * On legacy hierarchies, net_prio and net_cls controllers directly set
544 * attributes on each sock which can then be tested by the network layer.
545 * On the default hierarchy, each sock is associated with the cgroup it was
546 * created in and the networking layer can match the cgroup directly.
548 * To avoid carrying all three cgroup related fields separately in sock,
549 * sock_cgroup_data overloads (prioidx, classid) and the cgroup pointer.
550 * On boot, sock_cgroup_data records the cgroup that the sock was created
551 * in so that cgroup2 matches can be made; however, once either net_prio or
552 * net_cls starts being used, the area is overriden to carry prioidx and/or
553 * classid. The two modes are distinguished by whether the lowest bit is
554 * set. Clear bit indicates cgroup pointer while set bit prioidx and
557 * While userland may start using net_prio or net_cls at any time, once
558 * either is used, cgroup2 matching no longer works. There is no reason to
559 * mix the two and this is in line with how legacy and v2 compatibility is
560 * handled. On mode switch, cgroup references which are already being
561 * pointed to by socks may be leaked. While this can be remedied by adding
562 * synchronization around sock_cgroup_data, given that the number of leaked
563 * cgroups is bound and highly unlikely to be high, this seems to be the
566 struct sock_cgroup_data {
568 #ifdef __LITTLE_ENDIAN
588 * There's a theoretical window where the following accessors race with
589 * updaters and return part of the previous pointer as the prioidx or
590 * classid. Such races are short-lived and the result isn't critical.
592 static inline u16 sock_cgroup_prioidx(struct sock_cgroup_data *skcd)
594 /* fallback to 1 which is always the ID of the root cgroup */
595 return (skcd->is_data & 1) ? skcd->prioidx : 1;
598 static inline u32 sock_cgroup_classid(struct sock_cgroup_data *skcd)
600 /* fallback to 0 which is the unconfigured default classid */
601 return (skcd->is_data & 1) ? skcd->classid : 0;
605 * If invoked concurrently, the updaters may clobber each other. The
606 * caller is responsible for synchronization.
608 static inline void sock_cgroup_set_prioidx(struct sock_cgroup_data *skcd,
611 struct sock_cgroup_data skcd_buf = {{ .val = READ_ONCE(skcd->val) }};
613 if (sock_cgroup_prioidx(&skcd_buf) == prioidx)
616 if (!(skcd_buf.is_data & 1)) {
618 skcd_buf.is_data = 1;
621 skcd_buf.prioidx = prioidx;
622 WRITE_ONCE(skcd->val, skcd_buf.val); /* see sock_cgroup_ptr() */
625 static inline void sock_cgroup_set_classid(struct sock_cgroup_data *skcd,
628 struct sock_cgroup_data skcd_buf = {{ .val = READ_ONCE(skcd->val) }};
630 if (sock_cgroup_classid(&skcd_buf) == classid)
633 if (!(skcd_buf.is_data & 1)) {
635 skcd_buf.is_data = 1;
638 skcd_buf.classid = classid;
639 WRITE_ONCE(skcd->val, skcd_buf.val); /* see sock_cgroup_ptr() */
642 #else /* CONFIG_SOCK_CGROUP_DATA */
644 struct sock_cgroup_data {
647 #endif /* CONFIG_SOCK_CGROUP_DATA */
649 #endif /* _LINUX_CGROUP_DEFS_H */