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Linux/include/linux/cgroup-defs.h

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  1 /* SPDX-License-Identifier: GPL-2.0 */
  2 /*
  3  * linux/cgroup-defs.h - basic definitions for cgroup
  4  *
  5  * This file provides basic type and interface.  Include this file directly
  6  * only if necessary to avoid cyclic dependencies.
  7  */
  8 #ifndef _LINUX_CGROUP_DEFS_H
  9 #define _LINUX_CGROUP_DEFS_H
 10 
 11 #include <linux/limits.h>
 12 #include <linux/list.h>
 13 #include <linux/idr.h>
 14 #include <linux/wait.h>
 15 #include <linux/mutex.h>
 16 #include <linux/rcupdate.h>
 17 #include <linux/refcount.h>
 18 #include <linux/percpu-refcount.h>
 19 #include <linux/percpu-rwsem.h>
 20 #include <linux/u64_stats_sync.h>
 21 #include <linux/workqueue.h>
 22 #include <linux/bpf-cgroup.h>
 23 #include <linux/psi_types.h>
 24 
 25 #ifdef CONFIG_CGROUPS
 26 
 27 struct cgroup;
 28 struct cgroup_root;
 29 struct cgroup_subsys;
 30 struct cgroup_taskset;
 31 struct kernfs_node;
 32 struct kernfs_ops;
 33 struct kernfs_open_file;
 34 struct seq_file;
 35 struct poll_table_struct;
 36 
 37 #define MAX_CGROUP_TYPE_NAMELEN 32
 38 #define MAX_CGROUP_ROOT_NAMELEN 64
 39 #define MAX_CFTYPE_NAME         64
 40 
 41 /* define the enumeration of all cgroup subsystems */
 42 #define SUBSYS(_x) _x ## _cgrp_id,
 43 enum cgroup_subsys_id {
 44 #include <linux/cgroup_subsys.h>
 45         CGROUP_SUBSYS_COUNT,
 46 };
 47 #undef SUBSYS
 48 
 49 /* bits in struct cgroup_subsys_state flags field */
 50 enum {
 51         CSS_NO_REF      = (1 << 0), /* no reference counting for this css */
 52         CSS_ONLINE      = (1 << 1), /* between ->css_online() and ->css_offline() */
 53         CSS_RELEASED    = (1 << 2), /* refcnt reached zero, released */
 54         CSS_VISIBLE     = (1 << 3), /* css is visible to userland */
 55         CSS_DYING       = (1 << 4), /* css is dying */
 56 };
 57 
 58 /* bits in struct cgroup flags field */
 59 enum {
 60         /* Control Group requires release notifications to userspace */
 61         CGRP_NOTIFY_ON_RELEASE,
 62         /*
 63          * Clone the parent's configuration when creating a new child
 64          * cpuset cgroup.  For historical reasons, this option can be
 65          * specified at mount time and thus is implemented here.
 66          */
 67         CGRP_CPUSET_CLONE_CHILDREN,
 68 
 69         /* Control group has to be frozen. */
 70         CGRP_FREEZE,
 71 
 72         /* Cgroup is frozen. */
 73         CGRP_FROZEN,
 74 };
 75 
 76 /* cgroup_root->flags */
 77 enum {
 78         CGRP_ROOT_NOPREFIX      = (1 << 1), /* mounted subsystems have no named prefix */
 79         CGRP_ROOT_XATTR         = (1 << 2), /* supports extended attributes */
 80 
 81         /*
 82          * Consider namespaces as delegation boundaries.  If this flag is
 83          * set, controller specific interface files in a namespace root
 84          * aren't writeable from inside the namespace.
 85          */
 86         CGRP_ROOT_NS_DELEGATE   = (1 << 3),
 87 
 88         /*
 89          * Enable cpuset controller in v1 cgroup to use v2 behavior.
 90          */
 91         CGRP_ROOT_CPUSET_V2_MODE = (1 << 4),
 92 
 93         /*
 94          * Enable legacy local memory.events.
 95          */
 96         CGRP_ROOT_MEMORY_LOCAL_EVENTS = (1 << 5),
 97 };
 98 
 99 /* cftype->flags */
100 enum {
101         CFTYPE_ONLY_ON_ROOT     = (1 << 0),     /* only create on root cgrp */
102         CFTYPE_NOT_ON_ROOT      = (1 << 1),     /* don't create on root cgrp */
103         CFTYPE_NS_DELEGATABLE   = (1 << 2),     /* writeable beyond delegation boundaries */
104 
105         CFTYPE_NO_PREFIX        = (1 << 3),     /* (DON'T USE FOR NEW FILES) no subsys prefix */
106         CFTYPE_WORLD_WRITABLE   = (1 << 4),     /* (DON'T USE FOR NEW FILES) S_IWUGO */
107         CFTYPE_DEBUG            = (1 << 5),     /* create when cgroup_debug */
108 
109         /* internal flags, do not use outside cgroup core proper */
110         __CFTYPE_ONLY_ON_DFL    = (1 << 16),    /* only on default hierarchy */
111         __CFTYPE_NOT_ON_DFL     = (1 << 17),    /* not on default hierarchy */
112 };
113 
114 /*
115  * cgroup_file is the handle for a file instance created in a cgroup which
116  * is used, for example, to generate file changed notifications.  This can
117  * be obtained by setting cftype->file_offset.
118  */
119 struct cgroup_file {
120         /* do not access any fields from outside cgroup core */
121         struct kernfs_node *kn;
122         unsigned long notified_at;
123         struct timer_list notify_timer;
124 };
125 
126 /*
127  * Per-subsystem/per-cgroup state maintained by the system.  This is the
128  * fundamental structural building block that controllers deal with.
129  *
130  * Fields marked with "PI:" are public and immutable and may be accessed
131  * directly without synchronization.
132  */
133 struct cgroup_subsys_state {
134         /* PI: the cgroup that this css is attached to */
135         struct cgroup *cgroup;
136 
137         /* PI: the cgroup subsystem that this css is attached to */
138         struct cgroup_subsys *ss;
139 
140         /* reference count - access via css_[try]get() and css_put() */
141         struct percpu_ref refcnt;
142 
143         /* siblings list anchored at the parent's ->children */
144         struct list_head sibling;
145         struct list_head children;
146 
147         /* flush target list anchored at cgrp->rstat_css_list */
148         struct list_head rstat_css_node;
149 
150         /*
151          * PI: Subsys-unique ID.  0 is unused and root is always 1.  The
152          * matching css can be looked up using css_from_id().
153          */
154         int id;
155 
156         unsigned int flags;
157 
158         /*
159          * Monotonically increasing unique serial number which defines a
160          * uniform order among all csses.  It's guaranteed that all
161          * ->children lists are in the ascending order of ->serial_nr and
162          * used to allow interrupting and resuming iterations.
163          */
164         u64 serial_nr;
165 
166         /*
167          * Incremented by online self and children.  Used to guarantee that
168          * parents are not offlined before their children.
169          */
170         atomic_t online_cnt;
171 
172         /* percpu_ref killing and RCU release */
173         struct work_struct destroy_work;
174         struct rcu_work destroy_rwork;
175 
176         /*
177          * PI: the parent css.  Placed here for cache proximity to following
178          * fields of the containing structure.
179          */
180         struct cgroup_subsys_state *parent;
181 };
182 
183 /*
184  * A css_set is a structure holding pointers to a set of
185  * cgroup_subsys_state objects. This saves space in the task struct
186  * object and speeds up fork()/exit(), since a single inc/dec and a
187  * list_add()/del() can bump the reference count on the entire cgroup
188  * set for a task.
189  */
190 struct css_set {
191         /*
192          * Set of subsystem states, one for each subsystem. This array is
193          * immutable after creation apart from the init_css_set during
194          * subsystem registration (at boot time).
195          */
196         struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
197 
198         /* reference count */
199         refcount_t refcount;
200 
201         /*
202          * For a domain cgroup, the following points to self.  If threaded,
203          * to the matching cset of the nearest domain ancestor.  The
204          * dom_cset provides access to the domain cgroup and its csses to
205          * which domain level resource consumptions should be charged.
206          */
207         struct css_set *dom_cset;
208 
209         /* the default cgroup associated with this css_set */
210         struct cgroup *dfl_cgrp;
211 
212         /* internal task count, protected by css_set_lock */
213         int nr_tasks;
214 
215         /*
216          * Lists running through all tasks using this cgroup group.
217          * mg_tasks lists tasks which belong to this cset but are in the
218          * process of being migrated out or in.  Protected by
219          * css_set_rwsem, but, during migration, once tasks are moved to
220          * mg_tasks, it can be read safely while holding cgroup_mutex.
221          */
222         struct list_head tasks;
223         struct list_head mg_tasks;
224         struct list_head dying_tasks;
225 
226         /* all css_task_iters currently walking this cset */
227         struct list_head task_iters;
228 
229         /*
230          * On the default hierarhcy, ->subsys[ssid] may point to a css
231          * attached to an ancestor instead of the cgroup this css_set is
232          * associated with.  The following node is anchored at
233          * ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to
234          * iterate through all css's attached to a given cgroup.
235          */
236         struct list_head e_cset_node[CGROUP_SUBSYS_COUNT];
237 
238         /* all threaded csets whose ->dom_cset points to this cset */
239         struct list_head threaded_csets;
240         struct list_head threaded_csets_node;
241 
242         /*
243          * List running through all cgroup groups in the same hash
244          * slot. Protected by css_set_lock
245          */
246         struct hlist_node hlist;
247 
248         /*
249          * List of cgrp_cset_links pointing at cgroups referenced from this
250          * css_set.  Protected by css_set_lock.
251          */
252         struct list_head cgrp_links;
253 
254         /*
255          * List of csets participating in the on-going migration either as
256          * source or destination.  Protected by cgroup_mutex.
257          */
258         struct list_head mg_preload_node;
259         struct list_head mg_node;
260 
261         /*
262          * If this cset is acting as the source of migration the following
263          * two fields are set.  mg_src_cgrp and mg_dst_cgrp are
264          * respectively the source and destination cgroups of the on-going
265          * migration.  mg_dst_cset is the destination cset the target tasks
266          * on this cset should be migrated to.  Protected by cgroup_mutex.
267          */
268         struct cgroup *mg_src_cgrp;
269         struct cgroup *mg_dst_cgrp;
270         struct css_set *mg_dst_cset;
271 
272         /* dead and being drained, ignore for migration */
273         bool dead;
274 
275         /* For RCU-protected deletion */
276         struct rcu_head rcu_head;
277 };
278 
279 struct cgroup_base_stat {
280         struct task_cputime cputime;
281 };
282 
283 /*
284  * rstat - cgroup scalable recursive statistics.  Accounting is done
285  * per-cpu in cgroup_rstat_cpu which is then lazily propagated up the
286  * hierarchy on reads.
287  *
288  * When a stat gets updated, the cgroup_rstat_cpu and its ancestors are
289  * linked into the updated tree.  On the following read, propagation only
290  * considers and consumes the updated tree.  This makes reading O(the
291  * number of descendants which have been active since last read) instead of
292  * O(the total number of descendants).
293  *
294  * This is important because there can be a lot of (draining) cgroups which
295  * aren't active and stat may be read frequently.  The combination can
296  * become very expensive.  By propagating selectively, increasing reading
297  * frequency decreases the cost of each read.
298  *
299  * This struct hosts both the fields which implement the above -
300  * updated_children and updated_next - and the fields which track basic
301  * resource statistics on top of it - bsync, bstat and last_bstat.
302  */
303 struct cgroup_rstat_cpu {
304         /*
305          * ->bsync protects ->bstat.  These are the only fields which get
306          * updated in the hot path.
307          */
308         struct u64_stats_sync bsync;
309         struct cgroup_base_stat bstat;
310 
311         /*
312          * Snapshots at the last reading.  These are used to calculate the
313          * deltas to propagate to the global counters.
314          */
315         struct cgroup_base_stat last_bstat;
316 
317         /*
318          * Child cgroups with stat updates on this cpu since the last read
319          * are linked on the parent's ->updated_children through
320          * ->updated_next.
321          *
322          * In addition to being more compact, singly-linked list pointing
323          * to the cgroup makes it unnecessary for each per-cpu struct to
324          * point back to the associated cgroup.
325          *
326          * Protected by per-cpu cgroup_rstat_cpu_lock.
327          */
328         struct cgroup *updated_children;        /* terminated by self cgroup */
329         struct cgroup *updated_next;            /* NULL iff not on the list */
330 };
331 
332 struct cgroup_freezer_state {
333         /* Should the cgroup and its descendants be frozen. */
334         bool freeze;
335 
336         /* Should the cgroup actually be frozen? */
337         int e_freeze;
338 
339         /* Fields below are protected by css_set_lock */
340 
341         /* Number of frozen descendant cgroups */
342         int nr_frozen_descendants;
343 
344         /*
345          * Number of tasks, which are counted as frozen:
346          * frozen, SIGSTOPped, and PTRACEd.
347          */
348         int nr_frozen_tasks;
349 };
350 
351 struct cgroup {
352         /* self css with NULL ->ss, points back to this cgroup */
353         struct cgroup_subsys_state self;
354 
355         unsigned long flags;            /* "unsigned long" so bitops work */
356 
357         /*
358          * idr allocated in-hierarchy ID.
359          *
360          * ID 0 is not used, the ID of the root cgroup is always 1, and a
361          * new cgroup will be assigned with a smallest available ID.
362          *
363          * Allocating/Removing ID must be protected by cgroup_mutex.
364          */
365         int id;
366 
367         /*
368          * The depth this cgroup is at.  The root is at depth zero and each
369          * step down the hierarchy increments the level.  This along with
370          * ancestor_ids[] can determine whether a given cgroup is a
371          * descendant of another without traversing the hierarchy.
372          */
373         int level;
374 
375         /* Maximum allowed descent tree depth */
376         int max_depth;
377 
378         /*
379          * Keep track of total numbers of visible and dying descent cgroups.
380          * Dying cgroups are cgroups which were deleted by a user,
381          * but are still existing because someone else is holding a reference.
382          * max_descendants is a maximum allowed number of descent cgroups.
383          *
384          * nr_descendants and nr_dying_descendants are protected
385          * by cgroup_mutex and css_set_lock. It's fine to read them holding
386          * any of cgroup_mutex and css_set_lock; for writing both locks
387          * should be held.
388          */
389         int nr_descendants;
390         int nr_dying_descendants;
391         int max_descendants;
392 
393         /*
394          * Each non-empty css_set associated with this cgroup contributes
395          * one to nr_populated_csets.  The counter is zero iff this cgroup
396          * doesn't have any tasks.
397          *
398          * All children which have non-zero nr_populated_csets and/or
399          * nr_populated_children of their own contribute one to either
400          * nr_populated_domain_children or nr_populated_threaded_children
401          * depending on their type.  Each counter is zero iff all cgroups
402          * of the type in the subtree proper don't have any tasks.
403          */
404         int nr_populated_csets;
405         int nr_populated_domain_children;
406         int nr_populated_threaded_children;
407 
408         int nr_threaded_children;       /* # of live threaded child cgroups */
409 
410         struct kernfs_node *kn;         /* cgroup kernfs entry */
411         struct cgroup_file procs_file;  /* handle for "cgroup.procs" */
412         struct cgroup_file events_file; /* handle for "cgroup.events" */
413 
414         /*
415          * The bitmask of subsystems enabled on the child cgroups.
416          * ->subtree_control is the one configured through
417          * "cgroup.subtree_control" while ->child_ss_mask is the effective
418          * one which may have more subsystems enabled.  Controller knobs
419          * are made available iff it's enabled in ->subtree_control.
420          */
421         u16 subtree_control;
422         u16 subtree_ss_mask;
423         u16 old_subtree_control;
424         u16 old_subtree_ss_mask;
425 
426         /* Private pointers for each registered subsystem */
427         struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
428 
429         struct cgroup_root *root;
430 
431         /*
432          * List of cgrp_cset_links pointing at css_sets with tasks in this
433          * cgroup.  Protected by css_set_lock.
434          */
435         struct list_head cset_links;
436 
437         /*
438          * On the default hierarchy, a css_set for a cgroup with some
439          * susbsys disabled will point to css's which are associated with
440          * the closest ancestor which has the subsys enabled.  The
441          * following lists all css_sets which point to this cgroup's css
442          * for the given subsystem.
443          */
444         struct list_head e_csets[CGROUP_SUBSYS_COUNT];
445 
446         /*
447          * If !threaded, self.  If threaded, it points to the nearest
448          * domain ancestor.  Inside a threaded subtree, cgroups are exempt
449          * from process granularity and no-internal-task constraint.
450          * Domain level resource consumptions which aren't tied to a
451          * specific task are charged to the dom_cgrp.
452          */
453         struct cgroup *dom_cgrp;
454         struct cgroup *old_dom_cgrp;            /* used while enabling threaded */
455 
456         /* per-cpu recursive resource statistics */
457         struct cgroup_rstat_cpu __percpu *rstat_cpu;
458         struct list_head rstat_css_list;
459 
460         /* cgroup basic resource statistics */
461         struct cgroup_base_stat pending_bstat;  /* pending from children */
462         struct cgroup_base_stat bstat;
463         struct prev_cputime prev_cputime;       /* for printing out cputime */
464 
465         /*
466          * list of pidlists, up to two for each namespace (one for procs, one
467          * for tasks); created on demand.
468          */
469         struct list_head pidlists;
470         struct mutex pidlist_mutex;
471 
472         /* used to wait for offlining of csses */
473         wait_queue_head_t offline_waitq;
474 
475         /* used to schedule release agent */
476         struct work_struct release_agent_work;
477 
478         /* used to track pressure stalls */
479         struct psi_group psi;
480 
481         /* used to store eBPF programs */
482         struct cgroup_bpf bpf;
483 
484         /* If there is block congestion on this cgroup. */
485         atomic_t congestion_count;
486 
487         /* Used to store internal freezer state */
488         struct cgroup_freezer_state freezer;
489 
490         /* ids of the ancestors at each level including self */
491         int ancestor_ids[];
492 };
493 
494 /*
495  * A cgroup_root represents the root of a cgroup hierarchy, and may be
496  * associated with a kernfs_root to form an active hierarchy.  This is
497  * internal to cgroup core.  Don't access directly from controllers.
498  */
499 struct cgroup_root {
500         struct kernfs_root *kf_root;
501 
502         /* The bitmask of subsystems attached to this hierarchy */
503         unsigned int subsys_mask;
504 
505         /* Unique id for this hierarchy. */
506         int hierarchy_id;
507 
508         /* The root cgroup.  Root is destroyed on its release. */
509         struct cgroup cgrp;
510 
511         /* for cgrp->ancestor_ids[0] */
512         int cgrp_ancestor_id_storage;
513 
514         /* Number of cgroups in the hierarchy, used only for /proc/cgroups */
515         atomic_t nr_cgrps;
516 
517         /* A list running through the active hierarchies */
518         struct list_head root_list;
519 
520         /* Hierarchy-specific flags */
521         unsigned int flags;
522 
523         /* IDs for cgroups in this hierarchy */
524         struct idr cgroup_idr;
525 
526         /* The path to use for release notifications. */
527         char release_agent_path[PATH_MAX];
528 
529         /* The name for this hierarchy - may be empty */
530         char name[MAX_CGROUP_ROOT_NAMELEN];
531 };
532 
533 /*
534  * struct cftype: handler definitions for cgroup control files
535  *
536  * When reading/writing to a file:
537  *      - the cgroup to use is file->f_path.dentry->d_parent->d_fsdata
538  *      - the 'cftype' of the file is file->f_path.dentry->d_fsdata
539  */
540 struct cftype {
541         /*
542          * By convention, the name should begin with the name of the
543          * subsystem, followed by a period.  Zero length string indicates
544          * end of cftype array.
545          */
546         char name[MAX_CFTYPE_NAME];
547         unsigned long private;
548 
549         /*
550          * The maximum length of string, excluding trailing nul, that can
551          * be passed to write.  If < PAGE_SIZE-1, PAGE_SIZE-1 is assumed.
552          */
553         size_t max_write_len;
554 
555         /* CFTYPE_* flags */
556         unsigned int flags;
557 
558         /*
559          * If non-zero, should contain the offset from the start of css to
560          * a struct cgroup_file field.  cgroup will record the handle of
561          * the created file into it.  The recorded handle can be used as
562          * long as the containing css remains accessible.
563          */
564         unsigned int file_offset;
565 
566         /*
567          * Fields used for internal bookkeeping.  Initialized automatically
568          * during registration.
569          */
570         struct cgroup_subsys *ss;       /* NULL for cgroup core files */
571         struct list_head node;          /* anchored at ss->cfts */
572         struct kernfs_ops *kf_ops;
573 
574         int (*open)(struct kernfs_open_file *of);
575         void (*release)(struct kernfs_open_file *of);
576 
577         /*
578          * read_u64() is a shortcut for the common case of returning a
579          * single integer. Use it in place of read()
580          */
581         u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft);
582         /*
583          * read_s64() is a signed version of read_u64()
584          */
585         s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft);
586 
587         /* generic seq_file read interface */
588         int (*seq_show)(struct seq_file *sf, void *v);
589 
590         /* optional ops, implement all or none */
591         void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
592         void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
593         void (*seq_stop)(struct seq_file *sf, void *v);
594 
595         /*
596          * write_u64() is a shortcut for the common case of accepting
597          * a single integer (as parsed by simple_strtoull) from
598          * userspace. Use in place of write(); return 0 or error.
599          */
600         int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft,
601                          u64 val);
602         /*
603          * write_s64() is a signed version of write_u64()
604          */
605         int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft,
606                          s64 val);
607 
608         /*
609          * write() is the generic write callback which maps directly to
610          * kernfs write operation and overrides all other operations.
611          * Maximum write size is determined by ->max_write_len.  Use
612          * of_css/cft() to access the associated css and cft.
613          */
614         ssize_t (*write)(struct kernfs_open_file *of,
615                          char *buf, size_t nbytes, loff_t off);
616 
617         __poll_t (*poll)(struct kernfs_open_file *of,
618                          struct poll_table_struct *pt);
619 
620 #ifdef CONFIG_DEBUG_LOCK_ALLOC
621         struct lock_class_key   lockdep_key;
622 #endif
623 };
624 
625 /*
626  * Control Group subsystem type.
627  * See Documentation/admin-guide/cgroup-v1/cgroups.rst for details
628  */
629 struct cgroup_subsys {
630         struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);
631         int (*css_online)(struct cgroup_subsys_state *css);
632         void (*css_offline)(struct cgroup_subsys_state *css);
633         void (*css_released)(struct cgroup_subsys_state *css);
634         void (*css_free)(struct cgroup_subsys_state *css);
635         void (*css_reset)(struct cgroup_subsys_state *css);
636         void (*css_rstat_flush)(struct cgroup_subsys_state *css, int cpu);
637         int (*css_extra_stat_show)(struct seq_file *seq,
638                                    struct cgroup_subsys_state *css);
639 
640         int (*can_attach)(struct cgroup_taskset *tset);
641         void (*cancel_attach)(struct cgroup_taskset *tset);
642         void (*attach)(struct cgroup_taskset *tset);
643         void (*post_attach)(void);
644         int (*can_fork)(struct task_struct *task);
645         void (*cancel_fork)(struct task_struct *task);
646         void (*fork)(struct task_struct *task);
647         void (*exit)(struct task_struct *task);
648         void (*release)(struct task_struct *task);
649         void (*bind)(struct cgroup_subsys_state *root_css);
650 
651         bool early_init:1;
652 
653         /*
654          * If %true, the controller, on the default hierarchy, doesn't show
655          * up in "cgroup.controllers" or "cgroup.subtree_control", is
656          * implicitly enabled on all cgroups on the default hierarchy, and
657          * bypasses the "no internal process" constraint.  This is for
658          * utility type controllers which is transparent to userland.
659          *
660          * An implicit controller can be stolen from the default hierarchy
661          * anytime and thus must be okay with offline csses from previous
662          * hierarchies coexisting with csses for the current one.
663          */
664         bool implicit_on_dfl:1;
665 
666         /*
667          * If %true, the controller, supports threaded mode on the default
668          * hierarchy.  In a threaded subtree, both process granularity and
669          * no-internal-process constraint are ignored and a threaded
670          * controllers should be able to handle that.
671          *
672          * Note that as an implicit controller is automatically enabled on
673          * all cgroups on the default hierarchy, it should also be
674          * threaded.  implicit && !threaded is not supported.
675          */
676         bool threaded:1;
677 
678         /*
679          * If %false, this subsystem is properly hierarchical -
680          * configuration, resource accounting and restriction on a parent
681          * cgroup cover those of its children.  If %true, hierarchy support
682          * is broken in some ways - some subsystems ignore hierarchy
683          * completely while others are only implemented half-way.
684          *
685          * It's now disallowed to create nested cgroups if the subsystem is
686          * broken and cgroup core will emit a warning message on such
687          * cases.  Eventually, all subsystems will be made properly
688          * hierarchical and this will go away.
689          */
690         bool broken_hierarchy:1;
691         bool warned_broken_hierarchy:1;
692 
693         /* the following two fields are initialized automtically during boot */
694         int id;
695         const char *name;
696 
697         /* optional, initialized automatically during boot if not set */
698         const char *legacy_name;
699 
700         /* link to parent, protected by cgroup_lock() */
701         struct cgroup_root *root;
702 
703         /* idr for css->id */
704         struct idr css_idr;
705 
706         /*
707          * List of cftypes.  Each entry is the first entry of an array
708          * terminated by zero length name.
709          */
710         struct list_head cfts;
711 
712         /*
713          * Base cftypes which are automatically registered.  The two can
714          * point to the same array.
715          */
716         struct cftype *dfl_cftypes;     /* for the default hierarchy */
717         struct cftype *legacy_cftypes;  /* for the legacy hierarchies */
718 
719         /*
720          * A subsystem may depend on other subsystems.  When such subsystem
721          * is enabled on a cgroup, the depended-upon subsystems are enabled
722          * together if available.  Subsystems enabled due to dependency are
723          * not visible to userland until explicitly enabled.  The following
724          * specifies the mask of subsystems that this one depends on.
725          */
726         unsigned int depends_on;
727 };
728 
729 extern struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
730 
731 /**
732  * cgroup_threadgroup_change_begin - threadgroup exclusion for cgroups
733  * @tsk: target task
734  *
735  * Allows cgroup operations to synchronize against threadgroup changes
736  * using a percpu_rw_semaphore.
737  */
738 static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk)
739 {
740         percpu_down_read(&cgroup_threadgroup_rwsem);
741 }
742 
743 /**
744  * cgroup_threadgroup_change_end - threadgroup exclusion for cgroups
745  * @tsk: target task
746  *
747  * Counterpart of cgroup_threadcgroup_change_begin().
748  */
749 static inline void cgroup_threadgroup_change_end(struct task_struct *tsk)
750 {
751         percpu_up_read(&cgroup_threadgroup_rwsem);
752 }
753 
754 #else   /* CONFIG_CGROUPS */
755 
756 #define CGROUP_SUBSYS_COUNT 0
757 
758 static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk)
759 {
760         might_sleep();
761 }
762 
763 static inline void cgroup_threadgroup_change_end(struct task_struct *tsk) {}
764 
765 #endif  /* CONFIG_CGROUPS */
766 
767 #ifdef CONFIG_SOCK_CGROUP_DATA
768 
769 /*
770  * sock_cgroup_data is embedded at sock->sk_cgrp_data and contains
771  * per-socket cgroup information except for memcg association.
772  *
773  * On legacy hierarchies, net_prio and net_cls controllers directly set
774  * attributes on each sock which can then be tested by the network layer.
775  * On the default hierarchy, each sock is associated with the cgroup it was
776  * created in and the networking layer can match the cgroup directly.
777  *
778  * To avoid carrying all three cgroup related fields separately in sock,
779  * sock_cgroup_data overloads (prioidx, classid) and the cgroup pointer.
780  * On boot, sock_cgroup_data records the cgroup that the sock was created
781  * in so that cgroup2 matches can be made; however, once either net_prio or
782  * net_cls starts being used, the area is overriden to carry prioidx and/or
783  * classid.  The two modes are distinguished by whether the lowest bit is
784  * set.  Clear bit indicates cgroup pointer while set bit prioidx and
785  * classid.
786  *
787  * While userland may start using net_prio or net_cls at any time, once
788  * either is used, cgroup2 matching no longer works.  There is no reason to
789  * mix the two and this is in line with how legacy and v2 compatibility is
790  * handled.  On mode switch, cgroup references which are already being
791  * pointed to by socks may be leaked.  While this can be remedied by adding
792  * synchronization around sock_cgroup_data, given that the number of leaked
793  * cgroups is bound and highly unlikely to be high, this seems to be the
794  * better trade-off.
795  */
796 struct sock_cgroup_data {
797         union {
798 #ifdef __LITTLE_ENDIAN
799                 struct {
800                         u8      is_data;
801                         u8      padding;
802                         u16     prioidx;
803                         u32     classid;
804                 } __packed;
805 #else
806                 struct {
807                         u32     classid;
808                         u16     prioidx;
809                         u8      padding;
810                         u8      is_data;
811                 } __packed;
812 #endif
813                 u64             val;
814         };
815 };
816 
817 /*
818  * There's a theoretical window where the following accessors race with
819  * updaters and return part of the previous pointer as the prioidx or
820  * classid.  Such races are short-lived and the result isn't critical.
821  */
822 static inline u16 sock_cgroup_prioidx(const struct sock_cgroup_data *skcd)
823 {
824         /* fallback to 1 which is always the ID of the root cgroup */
825         return (skcd->is_data & 1) ? skcd->prioidx : 1;
826 }
827 
828 static inline u32 sock_cgroup_classid(const struct sock_cgroup_data *skcd)
829 {
830         /* fallback to 0 which is the unconfigured default classid */
831         return (skcd->is_data & 1) ? skcd->classid : 0;
832 }
833 
834 /*
835  * If invoked concurrently, the updaters may clobber each other.  The
836  * caller is responsible for synchronization.
837  */
838 static inline void sock_cgroup_set_prioidx(struct sock_cgroup_data *skcd,
839                                            u16 prioidx)
840 {
841         struct sock_cgroup_data skcd_buf = {{ .val = READ_ONCE(skcd->val) }};
842 
843         if (sock_cgroup_prioidx(&skcd_buf) == prioidx)
844                 return;
845 
846         if (!(skcd_buf.is_data & 1)) {
847                 skcd_buf.val = 0;
848                 skcd_buf.is_data = 1;
849         }
850 
851         skcd_buf.prioidx = prioidx;
852         WRITE_ONCE(skcd->val, skcd_buf.val);    /* see sock_cgroup_ptr() */
853 }
854 
855 static inline void sock_cgroup_set_classid(struct sock_cgroup_data *skcd,
856                                            u32 classid)
857 {
858         struct sock_cgroup_data skcd_buf = {{ .val = READ_ONCE(skcd->val) }};
859 
860         if (sock_cgroup_classid(&skcd_buf) == classid)
861                 return;
862 
863         if (!(skcd_buf.is_data & 1)) {
864                 skcd_buf.val = 0;
865                 skcd_buf.is_data = 1;
866         }
867 
868         skcd_buf.classid = classid;
869         WRITE_ONCE(skcd->val, skcd_buf.val);    /* see sock_cgroup_ptr() */
870 }
871 
872 #else   /* CONFIG_SOCK_CGROUP_DATA */
873 
874 struct sock_cgroup_data {
875 };
876 
877 #endif  /* CONFIG_SOCK_CGROUP_DATA */
878 
879 #endif  /* _LINUX_CGROUP_DEFS_H */
880 

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