1 #ifndef _LINUX_CGROUP_H 2 #define _LINUX_CGROUP_H 3 /* 4 * cgroup interface 5 * 6 * Copyright (C) 2003 BULL SA 7 * Copyright (C) 2004-2006 Silicon Graphics, Inc. 8 * 9 */ 10 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> 22 #include <linux/fs.h> 23 #include <linux/percpu-refcount.h> 24 #include <linux/seq_file.h> 25 26 #ifdef CONFIG_CGROUPS 27 28 struct cgroupfs_root; 29 struct cgroup_subsys; 30 struct inode; 31 struct cgroup; 32 33 extern int cgroup_init_early(void); 34 extern int cgroup_init(void); 35 extern void cgroup_fork(struct task_struct *p); 36 extern void cgroup_post_fork(struct task_struct *p); 37 extern void cgroup_exit(struct task_struct *p, int run_callbacks); 38 extern int cgroupstats_build(struct cgroupstats *stats, 39 struct dentry *dentry); 40 extern int cgroup_load_subsys(struct cgroup_subsys *ss); 41 extern void cgroup_unload_subsys(struct cgroup_subsys *ss); 42 43 extern int proc_cgroup_show(struct seq_file *, void *); 44 45 /* 46 * Define the enumeration of all cgroup subsystems. 47 * 48 * We define ids for builtin subsystems and then modular ones. 49 */ 50 #define SUBSYS(_x) _x ## _subsys_id, 51 enum cgroup_subsys_id { 52 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option) 53 #include <linux/cgroup_subsys.h> 54 #undef IS_SUBSYS_ENABLED 55 CGROUP_BUILTIN_SUBSYS_COUNT, 56 57 __CGROUP_SUBSYS_TEMP_PLACEHOLDER = CGROUP_BUILTIN_SUBSYS_COUNT - 1, 58 59 #define IS_SUBSYS_ENABLED(option) IS_MODULE(option) 60 #include <linux/cgroup_subsys.h> 61 #undef IS_SUBSYS_ENABLED 62 CGROUP_SUBSYS_COUNT, 63 }; 64 #undef SUBSYS 65 66 /* Per-subsystem/per-cgroup state maintained by the system. */ 67 struct cgroup_subsys_state { 68 /* the cgroup that this css is attached to */ 69 struct cgroup *cgroup; 70 71 /* the cgroup subsystem that this css is attached to */ 72 struct cgroup_subsys *ss; 73 74 /* reference count - access via css_[try]get() and css_put() */ 75 struct percpu_ref refcnt; 76 77 /* the parent css */ 78 struct cgroup_subsys_state *parent; 79 80 unsigned long flags; 81 82 /* percpu_ref killing and RCU release */ 83 struct rcu_head rcu_head; 84 struct work_struct destroy_work; 85 }; 86 87 /* bits in struct cgroup_subsys_state flags field */ 88 enum { 89 CSS_ROOT = (1 << 0), /* this CSS is the root of the subsystem */ 90 CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */ 91 }; 92 93 /** 94 * css_get - obtain a reference on the specified css 95 * @css: target css 96 * 97 * The caller must already have a reference. 98 */ 99 static inline void css_get(struct cgroup_subsys_state *css) 100 { 101 /* We don't need to reference count the root state */ 102 if (!(css->flags & CSS_ROOT)) 103 percpu_ref_get(&css->refcnt); 104 } 105 106 /** 107 * css_tryget - try to obtain a reference on the specified css 108 * @css: target css 109 * 110 * Obtain a reference on @css if it's alive. The caller naturally needs to 111 * ensure that @css is accessible but doesn't have to be holding a 112 * reference on it - IOW, RCU protected access is good enough for this 113 * function. Returns %true if a reference count was successfully obtained; 114 * %false otherwise. 115 */ 116 static inline bool css_tryget(struct cgroup_subsys_state *css) 117 { 118 if (css->flags & CSS_ROOT) 119 return true; 120 return percpu_ref_tryget(&css->refcnt); 121 } 122 123 /** 124 * css_put - put a css reference 125 * @css: target css 126 * 127 * Put a reference obtained via css_get() and css_tryget(). 128 */ 129 static inline void css_put(struct cgroup_subsys_state *css) 130 { 131 if (!(css->flags & CSS_ROOT)) 132 percpu_ref_put(&css->refcnt); 133 } 134 135 /* bits in struct cgroup flags field */ 136 enum { 137 /* Control Group is dead */ 138 CGRP_DEAD, 139 /* 140 * Control Group has previously had a child cgroup or a task, 141 * but no longer (only if CGRP_NOTIFY_ON_RELEASE is set) 142 */ 143 CGRP_RELEASABLE, 144 /* Control Group requires release notifications to userspace */ 145 CGRP_NOTIFY_ON_RELEASE, 146 /* 147 * Clone the parent's configuration when creating a new child 148 * cpuset cgroup. For historical reasons, this option can be 149 * specified at mount time and thus is implemented here. 150 */ 151 CGRP_CPUSET_CLONE_CHILDREN, 152 /* see the comment above CGRP_ROOT_SANE_BEHAVIOR for details */ 153 CGRP_SANE_BEHAVIOR, 154 }; 155 156 struct cgroup_name { 157 struct rcu_head rcu_head; 158 char name[]; 159 }; 160 161 struct cgroup { 162 unsigned long flags; /* "unsigned long" so bitops work */ 163 164 /* 165 * idr allocated in-hierarchy ID. 166 * 167 * The ID of the root cgroup is always 0, and a new cgroup 168 * will be assigned with a smallest available ID. 169 */ 170 int id; 171 172 /* the number of attached css's */ 173 int nr_css; 174 175 /* 176 * We link our 'sibling' struct into our parent's 'children'. 177 * Our children link their 'sibling' into our 'children'. 178 */ 179 struct list_head sibling; /* my parent's children */ 180 struct list_head children; /* my children */ 181 struct list_head files; /* my files */ 182 183 struct cgroup *parent; /* my parent */ 184 struct dentry *dentry; /* cgroup fs entry, RCU protected */ 185 186 /* 187 * Monotonically increasing unique serial number which defines a 188 * uniform order among all cgroups. It's guaranteed that all 189 * ->children lists are in the ascending order of ->serial_nr. 190 * It's used to allow interrupting and resuming iterations. 191 */ 192 u64 serial_nr; 193 194 /* 195 * This is a copy of dentry->d_name, and it's needed because 196 * we can't use dentry->d_name in cgroup_path(). 197 * 198 * You must acquire rcu_read_lock() to access cgrp->name, and 199 * the only place that can change it is rename(), which is 200 * protected by parent dir's i_mutex. 201 * 202 * Normally you should use cgroup_name() wrapper rather than 203 * access it directly. 204 */ 205 struct cgroup_name __rcu *name; 206 207 /* Private pointers for each registered subsystem */ 208 struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT]; 209 210 struct cgroupfs_root *root; 211 212 /* 213 * List of cgrp_cset_links pointing at css_sets with tasks in this 214 * cgroup. Protected by css_set_lock. 215 */ 216 struct list_head cset_links; 217 218 /* 219 * Linked list running through all cgroups that can 220 * potentially be reaped by the release agent. Protected by 221 * release_list_lock 222 */ 223 struct list_head release_list; 224 225 /* 226 * list of pidlists, up to two for each namespace (one for procs, one 227 * for tasks); created on demand. 228 */ 229 struct list_head pidlists; 230 struct mutex pidlist_mutex; 231 232 /* dummy css with NULL ->ss, points back to this cgroup */ 233 struct cgroup_subsys_state dummy_css; 234 235 /* For css percpu_ref killing and RCU-protected deletion */ 236 struct rcu_head rcu_head; 237 struct work_struct destroy_work; 238 239 /* directory xattrs */ 240 struct simple_xattrs xattrs; 241 }; 242 243 #define MAX_CGROUP_ROOT_NAMELEN 64 244 245 /* cgroupfs_root->flags */ 246 enum { 247 /* 248 * Unfortunately, cgroup core and various controllers are riddled 249 * with idiosyncrasies and pointless options. The following flag, 250 * when set, will force sane behavior - some options are forced on, 251 * others are disallowed, and some controllers will change their 252 * hierarchical or other behaviors. 253 * 254 * The set of behaviors affected by this flag are still being 255 * determined and developed and the mount option for this flag is 256 * prefixed with __DEVEL__. The prefix will be dropped once we 257 * reach the point where all behaviors are compatible with the 258 * planned unified hierarchy, which will automatically turn on this 259 * flag. 260 * 261 * The followings are the behaviors currently affected this flag. 262 * 263 * - Mount options "noprefix" and "clone_children" are disallowed. 264 * Also, cgroupfs file cgroup.clone_children is not created. 265 * 266 * - When mounting an existing superblock, mount options should 267 * match. 268 * 269 * - Remount is disallowed. 270 * 271 * - rename(2) is disallowed. 272 * 273 * - "tasks" is removed. Everything should be at process 274 * granularity. Use "cgroup.procs" instead. 275 * 276 * - "cgroup.procs" is not sorted. pids will be unique unless they 277 * got recycled inbetween reads. 278 * 279 * - "release_agent" and "notify_on_release" are removed. 280 * Replacement notification mechanism will be implemented. 281 * 282 * - cpuset: tasks will be kept in empty cpusets when hotplug happens 283 * and take masks of ancestors with non-empty cpus/mems, instead of 284 * being moved to an ancestor. 285 * 286 * - cpuset: a task can be moved into an empty cpuset, and again it 287 * takes masks of ancestors. 288 * 289 * - memcg: use_hierarchy is on by default and the cgroup file for 290 * the flag is not created. 291 * 292 * - blkcg: blk-throttle becomes properly hierarchical. 293 */ 294 CGRP_ROOT_SANE_BEHAVIOR = (1 << 0), 295 296 CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */ 297 CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */ 298 299 /* mount options live below bit 16 */ 300 CGRP_ROOT_OPTION_MASK = (1 << 16) - 1, 301 302 CGRP_ROOT_SUBSYS_BOUND = (1 << 16), /* subsystems finished binding */ 303 }; 304 305 /* 306 * A cgroupfs_root represents the root of a cgroup hierarchy, and may be 307 * associated with a superblock to form an active hierarchy. This is 308 * internal to cgroup core. Don't access directly from controllers. 309 */ 310 struct cgroupfs_root { 311 struct super_block *sb; 312 313 /* The bitmask of subsystems attached to this hierarchy */ 314 unsigned long subsys_mask; 315 316 /* Unique id for this hierarchy. */ 317 int hierarchy_id; 318 319 /* The root cgroup for this hierarchy */ 320 struct cgroup top_cgroup; 321 322 /* Tracks how many cgroups are currently defined in hierarchy.*/ 323 int number_of_cgroups; 324 325 /* A list running through the active hierarchies */ 326 struct list_head root_list; 327 328 /* Hierarchy-specific flags */ 329 unsigned long flags; 330 331 /* IDs for cgroups in this hierarchy */ 332 struct idr cgroup_idr; 333 334 /* The path to use for release notifications. */ 335 char release_agent_path[PATH_MAX]; 336 337 /* The name for this hierarchy - may be empty */ 338 char name[MAX_CGROUP_ROOT_NAMELEN]; 339 }; 340 341 /* 342 * A css_set is a structure holding pointers to a set of 343 * cgroup_subsys_state objects. This saves space in the task struct 344 * object and speeds up fork()/exit(), since a single inc/dec and a 345 * list_add()/del() can bump the reference count on the entire cgroup 346 * set for a task. 347 */ 348 349 struct css_set { 350 351 /* Reference count */ 352 atomic_t refcount; 353 354 /* 355 * List running through all cgroup groups in the same hash 356 * slot. Protected by css_set_lock 357 */ 358 struct hlist_node hlist; 359 360 /* 361 * List running through all tasks using this cgroup 362 * group. Protected by css_set_lock 363 */ 364 struct list_head tasks; 365 366 /* 367 * List of cgrp_cset_links pointing at cgroups referenced from this 368 * css_set. Protected by css_set_lock. 369 */ 370 struct list_head cgrp_links; 371 372 /* 373 * Set of subsystem states, one for each subsystem. This array 374 * is immutable after creation apart from the init_css_set 375 * during subsystem registration (at boot time) and modular subsystem 376 * loading/unloading. 377 */ 378 struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT]; 379 380 /* For RCU-protected deletion */ 381 struct rcu_head rcu_head; 382 }; 383 384 /* 385 * struct cftype: handler definitions for cgroup control files 386 * 387 * When reading/writing to a file: 388 * - the cgroup to use is file->f_dentry->d_parent->d_fsdata 389 * - the 'cftype' of the file is file->f_dentry->d_fsdata 390 */ 391 392 /* cftype->flags */ 393 enum { 394 CFTYPE_ONLY_ON_ROOT = (1 << 0), /* only create on root cgrp */ 395 CFTYPE_NOT_ON_ROOT = (1 << 1), /* don't create on root cgrp */ 396 CFTYPE_INSANE = (1 << 2), /* don't create if sane_behavior */ 397 CFTYPE_NO_PREFIX = (1 << 3), /* (DON'T USE FOR NEW FILES) no subsys prefix */ 398 }; 399 400 #define MAX_CFTYPE_NAME 64 401 402 struct cftype { 403 /* 404 * By convention, the name should begin with the name of the 405 * subsystem, followed by a period. Zero length string indicates 406 * end of cftype array. 407 */ 408 char name[MAX_CFTYPE_NAME]; 409 int private; 410 /* 411 * If not 0, file mode is set to this value, otherwise it will 412 * be figured out automatically 413 */ 414 umode_t mode; 415 416 /* 417 * If non-zero, defines the maximum length of string that can 418 * be passed to write_string; defaults to 64 419 */ 420 size_t max_write_len; 421 422 /* CFTYPE_* flags */ 423 unsigned int flags; 424 425 /* 426 * The subsys this file belongs to. Initialized automatically 427 * during registration. NULL for cgroup core files. 428 */ 429 struct cgroup_subsys *ss; 430 431 /* 432 * read_u64() is a shortcut for the common case of returning a 433 * single integer. Use it in place of read() 434 */ 435 u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft); 436 /* 437 * read_s64() is a signed version of read_u64() 438 */ 439 s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft); 440 441 /* generic seq_file read interface */ 442 int (*seq_show)(struct seq_file *sf, void *v); 443 444 /* optional ops, implement all or none */ 445 void *(*seq_start)(struct seq_file *sf, loff_t *ppos); 446 void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos); 447 void (*seq_stop)(struct seq_file *sf, void *v); 448 449 /* 450 * write_u64() is a shortcut for the common case of accepting 451 * a single integer (as parsed by simple_strtoull) from 452 * userspace. Use in place of write(); return 0 or error. 453 */ 454 int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft, 455 u64 val); 456 /* 457 * write_s64() is a signed version of write_u64() 458 */ 459 int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft, 460 s64 val); 461 462 /* 463 * write_string() is passed a nul-terminated kernelspace 464 * buffer of maximum length determined by max_write_len. 465 * Returns 0 or -ve error code. 466 */ 467 int (*write_string)(struct cgroup_subsys_state *css, struct cftype *cft, 468 const char *buffer); 469 /* 470 * trigger() callback can be used to get some kick from the 471 * userspace, when the actual string written is not important 472 * at all. The private field can be used to determine the 473 * kick type for multiplexing. 474 */ 475 int (*trigger)(struct cgroup_subsys_state *css, unsigned int event); 476 }; 477 478 /* 479 * cftype_sets describe cftypes belonging to a subsystem and are chained at 480 * cgroup_subsys->cftsets. Each cftset points to an array of cftypes 481 * terminated by zero length name. 482 */ 483 struct cftype_set { 484 struct list_head node; /* chained at subsys->cftsets */ 485 struct cftype *cfts; 486 }; 487 488 /* 489 * cgroupfs file entry, pointed to from leaf dentry->d_fsdata. Don't 490 * access directly. 491 */ 492 struct cfent { 493 struct list_head node; 494 struct dentry *dentry; 495 struct cftype *type; 496 struct cgroup_subsys_state *css; 497 498 /* file xattrs */ 499 struct simple_xattrs xattrs; 500 }; 501 502 /* seq_file->private points to the following, only ->priv is public */ 503 struct cgroup_open_file { 504 struct cfent *cfe; 505 void *priv; 506 }; 507 508 /* 509 * See the comment above CGRP_ROOT_SANE_BEHAVIOR for details. This 510 * function can be called as long as @cgrp is accessible. 511 */ 512 static inline bool cgroup_sane_behavior(const struct cgroup *cgrp) 513 { 514 return cgrp->root->flags & CGRP_ROOT_SANE_BEHAVIOR; 515 } 516 517 /* Caller should hold rcu_read_lock() */ 518 static inline const char *cgroup_name(const struct cgroup *cgrp) 519 { 520 return rcu_dereference(cgrp->name)->name; 521 } 522 523 static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq) 524 { 525 struct cgroup_open_file *of = seq->private; 526 return of->cfe->css; 527 } 528 529 static inline struct cftype *seq_cft(struct seq_file *seq) 530 { 531 struct cgroup_open_file *of = seq->private; 532 return of->cfe->type; 533 } 534 535 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts); 536 int cgroup_rm_cftypes(struct cftype *cfts); 537 538 bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor); 539 540 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen); 541 int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen); 542 543 int cgroup_task_count(const struct cgroup *cgrp); 544 545 /* 546 * Control Group taskset, used to pass around set of tasks to cgroup_subsys 547 * methods. 548 */ 549 struct cgroup_taskset; 550 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset); 551 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset); 552 struct cgroup_subsys_state *cgroup_taskset_cur_css(struct cgroup_taskset *tset, 553 int subsys_id); 554 int cgroup_taskset_size(struct cgroup_taskset *tset); 555 556 /** 557 * cgroup_taskset_for_each - iterate cgroup_taskset 558 * @task: the loop cursor 559 * @skip_css: skip if task's css matches this, %NULL to iterate through all 560 * @tset: taskset to iterate 561 */ 562 #define cgroup_taskset_for_each(task, skip_css, tset) \ 563 for ((task) = cgroup_taskset_first((tset)); (task); \ 564 (task) = cgroup_taskset_next((tset))) \ 565 if (!(skip_css) || \ 566 cgroup_taskset_cur_css((tset), \ 567 (skip_css)->ss->subsys_id) != (skip_css)) 568 569 /* 570 * Control Group subsystem type. 571 * See Documentation/cgroups/cgroups.txt for details 572 */ 573 574 struct cgroup_subsys { 575 struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css); 576 int (*css_online)(struct cgroup_subsys_state *css); 577 void (*css_offline)(struct cgroup_subsys_state *css); 578 void (*css_free)(struct cgroup_subsys_state *css); 579 580 int (*can_attach)(struct cgroup_subsys_state *css, 581 struct cgroup_taskset *tset); 582 void (*cancel_attach)(struct cgroup_subsys_state *css, 583 struct cgroup_taskset *tset); 584 void (*attach)(struct cgroup_subsys_state *css, 585 struct cgroup_taskset *tset); 586 void (*fork)(struct task_struct *task); 587 void (*exit)(struct cgroup_subsys_state *css, 588 struct cgroup_subsys_state *old_css, 589 struct task_struct *task); 590 void (*bind)(struct cgroup_subsys_state *root_css); 591 592 int subsys_id; 593 int disabled; 594 int early_init; 595 596 /* 597 * If %false, this subsystem is properly hierarchical - 598 * configuration, resource accounting and restriction on a parent 599 * cgroup cover those of its children. If %true, hierarchy support 600 * is broken in some ways - some subsystems ignore hierarchy 601 * completely while others are only implemented half-way. 602 * 603 * It's now disallowed to create nested cgroups if the subsystem is 604 * broken and cgroup core will emit a warning message on such 605 * cases. Eventually, all subsystems will be made properly 606 * hierarchical and this will go away. 607 */ 608 bool broken_hierarchy; 609 bool warned_broken_hierarchy; 610 611 #define MAX_CGROUP_TYPE_NAMELEN 32 612 const char *name; 613 614 /* link to parent, protected by cgroup_lock() */ 615 struct cgroupfs_root *root; 616 617 /* list of cftype_sets */ 618 struct list_head cftsets; 619 620 /* base cftypes, automatically [de]registered with subsys itself */ 621 struct cftype *base_cftypes; 622 struct cftype_set base_cftset; 623 624 /* should be defined only by modular subsystems */ 625 struct module *module; 626 }; 627 628 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys; 629 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option) 630 #include <linux/cgroup_subsys.h> 631 #undef IS_SUBSYS_ENABLED 632 #undef SUBSYS 633 634 /** 635 * css_parent - find the parent css 636 * @css: the target cgroup_subsys_state 637 * 638 * Return the parent css of @css. This function is guaranteed to return 639 * non-NULL parent as long as @css isn't the root. 640 */ 641 static inline 642 struct cgroup_subsys_state *css_parent(struct cgroup_subsys_state *css) 643 { 644 return css->parent; 645 } 646 647 /** 648 * task_css_set_check - obtain a task's css_set with extra access conditions 649 * @task: the task to obtain css_set for 650 * @__c: extra condition expression to be passed to rcu_dereference_check() 651 * 652 * A task's css_set is RCU protected, initialized and exited while holding 653 * task_lock(), and can only be modified while holding both cgroup_mutex 654 * and task_lock() while the task is alive. This macro verifies that the 655 * caller is inside proper critical section and returns @task's css_set. 656 * 657 * The caller can also specify additional allowed conditions via @__c, such 658 * as locks used during the cgroup_subsys::attach() methods. 659 */ 660 #ifdef CONFIG_PROVE_RCU 661 extern struct mutex cgroup_mutex; 662 #define task_css_set_check(task, __c) \ 663 rcu_dereference_check((task)->cgroups, \ 664 lockdep_is_held(&(task)->alloc_lock) || \ 665 lockdep_is_held(&cgroup_mutex) || (__c)) 666 #else 667 #define task_css_set_check(task, __c) \ 668 rcu_dereference((task)->cgroups) 669 #endif 670 671 /** 672 * task_css_check - obtain css for (task, subsys) w/ extra access conds 673 * @task: the target task 674 * @subsys_id: the target subsystem ID 675 * @__c: extra condition expression to be passed to rcu_dereference_check() 676 * 677 * Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The 678 * synchronization rules are the same as task_css_set_check(). 679 */ 680 #define task_css_check(task, subsys_id, __c) \ 681 task_css_set_check((task), (__c))->subsys[(subsys_id)] 682 683 /** 684 * task_css_set - obtain a task's css_set 685 * @task: the task to obtain css_set for 686 * 687 * See task_css_set_check(). 688 */ 689 static inline struct css_set *task_css_set(struct task_struct *task) 690 { 691 return task_css_set_check(task, false); 692 } 693 694 /** 695 * task_css - obtain css for (task, subsys) 696 * @task: the target task 697 * @subsys_id: the target subsystem ID 698 * 699 * See task_css_check(). 700 */ 701 static inline struct cgroup_subsys_state *task_css(struct task_struct *task, 702 int subsys_id) 703 { 704 return task_css_check(task, subsys_id, false); 705 } 706 707 static inline struct cgroup *task_cgroup(struct task_struct *task, 708 int subsys_id) 709 { 710 return task_css(task, subsys_id)->cgroup; 711 } 712 713 struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos, 714 struct cgroup_subsys_state *parent); 715 716 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss); 717 718 /** 719 * css_for_each_child - iterate through children of a css 720 * @pos: the css * to use as the loop cursor 721 * @parent: css whose children to walk 722 * 723 * Walk @parent's children. Must be called under rcu_read_lock(). A child 724 * css which hasn't finished ->css_online() or already has finished 725 * ->css_offline() may show up during traversal and it's each subsystem's 726 * responsibility to verify that each @pos is alive. 727 * 728 * If a subsystem synchronizes against the parent in its ->css_online() and 729 * before starting iterating, a css which finished ->css_online() is 730 * guaranteed to be visible in the future iterations. 731 * 732 * It is allowed to temporarily drop RCU read lock during iteration. The 733 * caller is responsible for ensuring that @pos remains accessible until 734 * the start of the next iteration by, for example, bumping the css refcnt. 735 */ 736 #define css_for_each_child(pos, parent) \ 737 for ((pos) = css_next_child(NULL, (parent)); (pos); \ 738 (pos) = css_next_child((pos), (parent))) 739 740 struct cgroup_subsys_state * 741 css_next_descendant_pre(struct cgroup_subsys_state *pos, 742 struct cgroup_subsys_state *css); 743 744 struct cgroup_subsys_state * 745 css_rightmost_descendant(struct cgroup_subsys_state *pos); 746 747 /** 748 * css_for_each_descendant_pre - pre-order walk of a css's descendants 749 * @pos: the css * to use as the loop cursor 750 * @root: css whose descendants to walk 751 * 752 * Walk @root's descendants. @root is included in the iteration and the 753 * first node to be visited. Must be called under rcu_read_lock(). A 754 * descendant css which hasn't finished ->css_online() or already has 755 * finished ->css_offline() may show up during traversal and it's each 756 * subsystem's responsibility to verify that each @pos is alive. 757 * 758 * If a subsystem synchronizes against the parent in its ->css_online() and 759 * before starting iterating, and synchronizes against @pos on each 760 * iteration, any descendant css which finished ->css_online() is 761 * guaranteed to be visible in the future iterations. 762 * 763 * In other words, the following guarantees that a descendant can't escape 764 * state updates of its ancestors. 765 * 766 * my_online(@css) 767 * { 768 * Lock @css's parent and @css; 769 * Inherit state from the parent; 770 * Unlock both. 771 * } 772 * 773 * my_update_state(@css) 774 * { 775 * css_for_each_descendant_pre(@pos, @css) { 776 * Lock @pos; 777 * if (@pos == @css) 778 * Update @css's state; 779 * else 780 * Verify @pos is alive and inherit state from its parent; 781 * Unlock @pos; 782 * } 783 * } 784 * 785 * As long as the inheriting step, including checking the parent state, is 786 * enclosed inside @pos locking, double-locking the parent isn't necessary 787 * while inheriting. The state update to the parent is guaranteed to be 788 * visible by walking order and, as long as inheriting operations to the 789 * same @pos are atomic to each other, multiple updates racing each other 790 * still result in the correct state. It's guaranateed that at least one 791 * inheritance happens for any css after the latest update to its parent. 792 * 793 * If checking parent's state requires locking the parent, each inheriting 794 * iteration should lock and unlock both @pos->parent and @pos. 795 * 796 * Alternatively, a subsystem may choose to use a single global lock to 797 * synchronize ->css_online() and ->css_offline() against tree-walking 798 * operations. 799 * 800 * It is allowed to temporarily drop RCU read lock during iteration. The 801 * caller is responsible for ensuring that @pos remains accessible until 802 * the start of the next iteration by, for example, bumping the css refcnt. 803 */ 804 #define css_for_each_descendant_pre(pos, css) \ 805 for ((pos) = css_next_descendant_pre(NULL, (css)); (pos); \ 806 (pos) = css_next_descendant_pre((pos), (css))) 807 808 struct cgroup_subsys_state * 809 css_next_descendant_post(struct cgroup_subsys_state *pos, 810 struct cgroup_subsys_state *css); 811 812 /** 813 * css_for_each_descendant_post - post-order walk of a css's descendants 814 * @pos: the css * to use as the loop cursor 815 * @css: css whose descendants to walk 816 * 817 * Similar to css_for_each_descendant_pre() but performs post-order 818 * traversal instead. @root is included in the iteration and the last 819 * node to be visited. Note that the walk visibility guarantee described 820 * in pre-order walk doesn't apply the same to post-order walks. 821 */ 822 #define css_for_each_descendant_post(pos, css) \ 823 for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \ 824 (pos) = css_next_descendant_post((pos), (css))) 825 826 /* A css_task_iter should be treated as an opaque object */ 827 struct css_task_iter { 828 struct cgroup_subsys_state *origin_css; 829 struct list_head *cset_link; 830 struct list_head *task; 831 }; 832 833 void css_task_iter_start(struct cgroup_subsys_state *css, 834 struct css_task_iter *it); 835 struct task_struct *css_task_iter_next(struct css_task_iter *it); 836 void css_task_iter_end(struct css_task_iter *it); 837 838 int css_scan_tasks(struct cgroup_subsys_state *css, 839 bool (*test)(struct task_struct *, void *), 840 void (*process)(struct task_struct *, void *), 841 void *data, struct ptr_heap *heap); 842 843 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); 844 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from); 845 846 struct cgroup_subsys_state *css_from_dir(struct dentry *dentry, 847 struct cgroup_subsys *ss); 848 849 #else /* !CONFIG_CGROUPS */ 850 851 static inline int cgroup_init_early(void) { return 0; } 852 static inline int cgroup_init(void) { return 0; } 853 static inline void cgroup_fork(struct task_struct *p) {} 854 static inline void cgroup_post_fork(struct task_struct *p) {} 855 static inline void cgroup_exit(struct task_struct *p, int callbacks) {} 856 857 static inline int cgroupstats_build(struct cgroupstats *stats, 858 struct dentry *dentry) 859 { 860 return -EINVAL; 861 } 862 863 /* No cgroups - nothing to do */ 864 static inline int cgroup_attach_task_all(struct task_struct *from, 865 struct task_struct *t) 866 { 867 return 0; 868 } 869 870 #endif /* !CONFIG_CGROUPS */ 871 872 #endif /* _LINUX_CGROUP_H */ 873