1/* SPDX-License-Identifier: GPL-2.0 */ 2#ifndef _LINUX_LIST_H 3#define _LINUX_LIST_H 4 5#include <linux/types.h> 6#include <linux/stddef.h> 7#include <linux/poison.h> 8#include <linux/const.h> 9#include <linux/kernel.h> 10 11/* 12 * Simple doubly linked list implementation. 13 * 14 * Some of the internal functions ("__xxx") are useful when 15 * manipulating whole lists rather than single entries, as 16 * sometimes we already know the next/prev entries and we can 17 * generate better code by using them directly rather than 18 * using the generic single-entry routines. 19 */ 20 21#define LIST_HEAD_INIT(name) { &(name), &(name) } 22 23#define LIST_HEAD(name) \ 24 struct list_head name = LIST_HEAD_INIT(name) 25 26/** 27 * INIT_LIST_HEAD - Initialize a list_head structure 28 * @list: list_head structure to be initialized. 29 * 30 * Initializes the list_head to point to itself. If it is a list header, 31 * the result is an empty list. 32 */ 33static inline void INIT_LIST_HEAD(struct list_head *list) 34{ 35 WRITE_ONCE(list->next, list); 36 list->prev = list; 37} 38 39#ifdef CONFIG_DEBUG_LIST 40extern bool __list_add_valid(struct list_head *new, 41 struct list_head *prev, 42 struct list_head *next); 43extern bool __list_del_entry_valid(struct list_head *entry); 44#else 45static inline bool __list_add_valid(struct list_head *new, 46 struct list_head *prev, 47 struct list_head *next) 48{ 49 return true; 50} 51static inline bool __list_del_entry_valid(struct list_head *entry) 52{ 53 return true; 54} 55#endif 56 57/* 58 * Insert a new entry between two known consecutive entries. 59 * 60 * This is only for internal list manipulation where we know 61 * the prev/next entries already! 62 */ 63static inline void __list_add(struct list_head *new, 64 struct list_head *prev, 65 struct list_head *next) 66{ 67 if (!__list_add_valid(new, prev, next)) 68 return; 69 70 next->prev = new; 71 new->next = next; 72 new->prev = prev; 73 WRITE_ONCE(prev->next, new); 74} 75 76/** 77 * list_add - add a new entry 78 * @new: new entry to be added 79 * @head: list head to add it after 80 * 81 * Insert a new entry after the specified head. 82 * This is good for implementing stacks. 83 */ 84static inline void list_add(struct list_head *new, struct list_head *head) 85{ 86 __list_add(new, head, head->next); 87} 88 89 90/** 91 * list_add_tail - add a new entry 92 * @new: new entry to be added 93 * @head: list head to add it before 94 * 95 * Insert a new entry before the specified head. 96 * This is useful for implementing queues. 97 */ 98static inline void list_add_tail(struct list_head *new, struct list_head *head) 99{ 100 __list_add(new, head->prev, head); 101} 102 103/* 104 * Delete a list entry by making the prev/next entries 105 * point to each other. 106 * 107 * This is only for internal list manipulation where we know 108 * the prev/next entries already! 109 */ 110static inline void __list_del(struct list_head * prev, struct list_head * next) 111{ 112 next->prev = prev; 113 WRITE_ONCE(prev->next, next); 114} 115 116/* 117 * Delete a list entry and clear the 'prev' pointer. 118 * 119 * This is a special-purpose list clearing method used in the networking code 120 * for lists allocated as per-cpu, where we don't want to incur the extra 121 * WRITE_ONCE() overhead of a regular list_del_init(). The code that uses this 122 * needs to check the node 'prev' pointer instead of calling list_empty(). 123 */ 124static inline void __list_del_clearprev(struct list_head *entry) 125{ 126 __list_del(entry->prev, entry->next); 127 entry->prev = NULL; 128} 129 130static inline void __list_del_entry(struct list_head *entry) 131{ 132 if (!__list_del_entry_valid(entry)) 133 return; 134 135 __list_del(entry->prev, entry->next); 136} 137 138/** 139 * list_del - deletes entry from list. 140 * @entry: the element to delete from the list. 141 * Note: list_empty() on entry does not return true after this, the entry is 142 * in an undefined state. 143 */ 144static inline void list_del(struct list_head *entry) 145{ 146 __list_del_entry(entry); 147 entry->next = LIST_POISON1; 148 entry->prev = LIST_POISON2; 149} 150 151/** 152 * list_replace - replace old entry by new one 153 * @old : the element to be replaced 154 * @new : the new element to insert 155 * 156 * If @old was empty, it will be overwritten. 157 */ 158static inline void list_replace(struct list_head *old, 159 struct list_head *new) 160{ 161 new->next = old->next; 162 new->next->prev = new; 163 new->prev = old->prev; 164 new->prev->next = new; 165} 166 167/** 168 * list_replace_init - replace old entry by new one and initialize the old one 169 * @old : the element to be replaced 170 * @new : the new element to insert 171 * 172 * If @old was empty, it will be overwritten. 173 */ 174static inline void list_replace_init(struct list_head *old, 175 struct list_head *new) 176{ 177 list_replace(old, new); 178 INIT_LIST_HEAD(old); 179} 180 181/** 182 * list_swap - replace entry1 with entry2 and re-add entry1 at entry2's position 183 * @entry1: the location to place entry2 184 * @entry2: the location to place entry1 185 */ 186static inline void list_swap(struct list_head *entry1, 187 struct list_head *entry2) 188{ 189 struct list_head *pos = entry2->prev; 190 191 list_del(entry2); 192 list_replace(entry1, entry2); 193 if (pos == entry1) 194 pos = entry2; 195 list_add(entry1, pos); 196} 197 198/** 199 * list_del_init - deletes entry from list and reinitialize it. 200 * @entry: the element to delete from the list. 201 */ 202static inline void list_del_init(struct list_head *entry) 203{ 204 __list_del_entry(entry); 205 INIT_LIST_HEAD(entry); 206} 207 208/** 209 * list_move - delete from one list and add as another's head 210 * @list: the entry to move 211 * @head: the head that will precede our entry 212 */ 213static inline void list_move(struct list_head *list, struct list_head *head) 214{ 215 __list_del_entry(list); 216 list_add(list, head); 217} 218 219/** 220 * list_move_tail - delete from one list and add as another's tail 221 * @list: the entry to move 222 * @head: the head that will follow our entry 223 */ 224static inline void list_move_tail(struct list_head *list, 225 struct list_head *head) 226{ 227 __list_del_entry(list); 228 list_add_tail(list, head); 229} 230 231/** 232 * list_bulk_move_tail - move a subsection of a list to its tail 233 * @head: the head that will follow our entry 234 * @first: first entry to move 235 * @last: last entry to move, can be the same as first 236 * 237 * Move all entries between @first and including @last before @head. 238 * All three entries must belong to the same linked list. 239 */ 240static inline void list_bulk_move_tail(struct list_head *head, 241 struct list_head *first, 242 struct list_head *last) 243{ 244 first->prev->next = last->next; 245 last->next->prev = first->prev; 246 247 head->prev->next = first; 248 first->prev = head->prev; 249 250 last->next = head; 251 head->prev = last; 252} 253 254/** 255 * list_is_first -- tests whether @list is the first entry in list @head 256 * @list: the entry to test 257 * @head: the head of the list 258 */ 259static inline int list_is_first(const struct list_head *list, 260 const struct list_head *head) 261{ 262 return list->prev == head; 263} 264 265/** 266 * list_is_last - tests whether @list is the last entry in list @head 267 * @list: the entry to test 268 * @head: the head of the list 269 */ 270static inline int list_is_last(const struct list_head *list, 271 const struct list_head *head) 272{ 273 return list->next == head; 274} 275 276/** 277 * list_empty - tests whether a list is empty 278 * @head: the list to test. 279 */ 280static inline int list_empty(const struct list_head *head) 281{ 282 return READ_ONCE(head->next) == head; 283} 284 285/** 286 * list_del_init_careful - deletes entry from list and reinitialize it. 287 * @entry: the element to delete from the list. 288 * 289 * This is the same as list_del_init(), except designed to be used 290 * together with list_empty_careful() in a way to guarantee ordering 291 * of other memory operations. 292 * 293 * Any memory operations done before a list_del_init_careful() are 294 * guaranteed to be visible after a list_empty_careful() test. 295 */ 296static inline void list_del_init_careful(struct list_head *entry) 297{ 298 __list_del_entry(entry); 299 entry->prev = entry; 300 smp_store_release(&entry->next, entry); 301} 302 303/** 304 * list_empty_careful - tests whether a list is empty and not being modified 305 * @head: the list to test 306 * 307 * Description: 308 * tests whether a list is empty _and_ checks that no other CPU might be 309 * in the process of modifying either member (next or prev) 310 * 311 * NOTE: using list_empty_careful() without synchronization 312 * can only be safe if the only activity that can happen 313 * to the list entry is list_del_init(). Eg. it cannot be used 314 * if another CPU could re-list_add() it. 315 */ 316static inline int list_empty_careful(const struct list_head *head) 317{ 318 struct list_head *next = smp_load_acquire(&head->next); 319 return (next == head) && (next == head->prev); 320} 321 322/** 323 * list_rotate_left - rotate the list to the left 324 * @head: the head of the list 325 */ 326static inline void list_rotate_left(struct list_head *head) 327{ 328 struct list_head *first; 329 330 if (!list_empty(head)) { 331 first = head->next; 332 list_move_tail(first, head); 333 } 334} 335 336/** 337 * list_rotate_to_front() - Rotate list to specific item. 338 * @list: The desired new front of the list. 339 * @head: The head of the list. 340 * 341 * Rotates list so that @list becomes the new front of the list. 342 */ 343static inline void list_rotate_to_front(struct list_head *list, 344 struct list_head *head) 345{ 346 /* 347 * Deletes the list head from the list denoted by @head and 348 * places it as the tail of @list, this effectively rotates the 349 * list so that @list is at the front. 350 */ 351 list_move_tail(head, list); 352} 353 354/** 355 * list_is_singular - tests whether a list has just one entry. 356 * @head: the list to test. 357 */ 358static inline int list_is_singular(const struct list_head *head) 359{ 360 return !list_empty(head) && (head->next == head->prev); 361} 362 363static inline void __list_cut_position(struct list_head *list, 364 struct list_head *head, struct list_head *entry) 365{ 366 struct list_head *new_first = entry->next; 367 list->next = head->next; 368 list->next->prev = list; 369 list->prev = entry; 370 entry->next = list; 371 head->next = new_first; 372 new_first->prev = head; 373} 374 375/** 376 * list_cut_position - cut a list into two 377 * @list: a new list to add all removed entries 378 * @head: a list with entries 379 * @entry: an entry within head, could be the head itself 380 * and if so we won't cut the list 381 * 382 * This helper moves the initial part of @head, up to and 383 * including @entry, from @head to @list. You should 384 * pass on @entry an element you know is on @head. @list 385 * should be an empty list or a list you do not care about 386 * losing its data. 387 * 388 */ 389static inline void list_cut_position(struct list_head *list, 390 struct list_head *head, struct list_head *entry) 391{ 392 if (list_empty(head)) 393 return; 394 if (list_is_singular(head) && 395 (head->next != entry && head != entry)) 396 return; 397 if (entry == head) 398 INIT_LIST_HEAD(list); 399 else 400 __list_cut_position(list, head, entry); 401} 402 403/** 404 * list_cut_before - cut a list into two, before given entry 405 * @list: a new list to add all removed entries 406 * @head: a list with entries 407 * @entry: an entry within head, could be the head itself 408 * 409 * This helper moves the initial part of @head, up to but 410 * excluding @entry, from @head to @list. You should pass 411 * in @entry an element you know is on @head. @list should 412 * be an empty list or a list you do not care about losing 413 * its data. 414 * If @entry == @head, all entries on @head are moved to 415 * @list. 416 */ 417static inline void list_cut_before(struct list_head *list, 418 struct list_head *head, 419 struct list_head *entry) 420{ 421 if (head->next == entry) { 422 INIT_LIST_HEAD(list); 423 return; 424 } 425 list->next = head->next; 426 list->next->prev = list; 427 list->prev = entry->prev; 428 list->prev->next = list; 429 head->next = entry; 430 entry->prev = head; 431} 432 433static inline void __list_splice(const struct list_head *list, 434 struct list_head *prev, 435 struct list_head *next) 436{ 437 struct list_head *first = list->next; 438 struct list_head *last = list->prev; 439 440 first->prev = prev; 441 prev->next = first; 442 443 last->next = next; 444 next->prev = last; 445} 446 447/** 448 * list_splice - join two lists, this is designed for stacks 449 * @list: the new list to add. 450 * @head: the place to add it in the first list. 451 */ 452static inline void list_splice(const struct list_head *list, 453 struct list_head *head) 454{ 455 if (!list_empty(list)) 456 __list_splice(list, head, head->next); 457} 458 459/** 460 * list_splice_tail - join two lists, each list being a queue 461 * @list: the new list to add. 462 * @head: the place to add it in the first list. 463 */ 464static inline void list_splice_tail(struct list_head *list, 465 struct list_head *head) 466{ 467 if (!list_empty(list)) 468 __list_splice(list, head->prev, head); 469} 470 471/** 472 * list_splice_init - join two lists and reinitialise the emptied list. 473 * @list: the new list to add. 474 * @head: the place to add it in the first list. 475 * 476 * The list at @list is reinitialised 477 */ 478static inline void list_splice_init(struct list_head *list, 479 struct list_head *head) 480{ 481 if (!list_empty(list)) { 482 __list_splice(list, head, head->next); 483 INIT_LIST_HEAD(list); 484 } 485} 486 487/** 488 * list_splice_tail_init - join two lists and reinitialise the emptied list 489 * @list: the new list to add. 490 * @head: the place to add it in the first list. 491 * 492 * Each of the lists is a queue. 493 * The list at @list is reinitialised 494 */ 495static inline void list_splice_tail_init(struct list_head *list, 496 struct list_head *head) 497{ 498 if (!list_empty(list)) { 499 __list_splice(list, head->prev, head); 500 INIT_LIST_HEAD(list); 501 } 502} 503 504/** 505 * list_entry - get the struct for this entry 506 * @ptr: the &struct list_head pointer. 507 * @type: the type of the struct this is embedded in. 508 * @member: the name of the list_head within the struct. 509 */ 510#define list_entry(ptr, type, member) \ 511 container_of(ptr, type, member) 512 513/** 514 * list_first_entry - get the first element from a list 515 * @ptr: the list head to take the element from. 516 * @type: the type of the struct this is embedded in. 517 * @member: the name of the list_head within the struct. 518 * 519 * Note, that list is expected to be not empty. 520 */ 521#define list_first_entry(ptr, type, member) \ 522 list_entry((ptr)->next, type, member) 523 524/** 525 * list_last_entry - get the last element from a list 526 * @ptr: the list head to take the element from. 527 * @type: the type of the struct this is embedded in. 528 * @member: the name of the list_head within the struct. 529 * 530 * Note, that list is expected to be not empty. 531 */ 532#define list_last_entry(ptr, type, member) \ 533 list_entry((ptr)->prev, type, member) 534 535/** 536 * list_first_entry_or_null - get the first element from a list 537 * @ptr: the list head to take the element from. 538 * @type: the type of the struct this is embedded in. 539 * @member: the name of the list_head within the struct. 540 * 541 * Note that if the list is empty, it returns NULL. 542 */ 543#define list_first_entry_or_null(ptr, type, member) ({ \ 544 struct list_head *head__ = (ptr); \ 545 struct list_head *pos__ = READ_ONCE(head__->next); \ 546 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \ 547}) 548 549/** 550 * list_next_entry - get the next element in list 551 * @pos: the type * to cursor 552 * @member: the name of the list_head within the struct. 553 */ 554#define list_next_entry(pos, member) \ 555 list_entry((pos)->member.next, typeof(*(pos)), member) 556 557/** 558 * list_prev_entry - get the prev element in list 559 * @pos: the type * to cursor 560 * @member: the name of the list_head within the struct. 561 */ 562#define list_prev_entry(pos, member) \ 563 list_entry((pos)->member.prev, typeof(*(pos)), member) 564 565/** 566 * list_for_each - iterate over a list 567 * @pos: the &struct list_head to use as a loop cursor. 568 * @head: the head for your list. 569 */ 570#define list_for_each(pos, head) \ 571 for (pos = (head)->next; pos != (head); pos = pos->next) 572 573/** 574 * list_for_each_continue - continue iteration over a list 575 * @pos: the &struct list_head to use as a loop cursor. 576 * @head: the head for your list. 577 * 578 * Continue to iterate over a list, continuing after the current position. 579 */ 580#define list_for_each_continue(pos, head) \ 581 for (pos = pos->next; pos != (head); pos = pos->next) 582 583/** 584 * list_for_each_prev - iterate over a list backwards 585 * @pos: the &struct list_head to use as a loop cursor. 586 * @head: the head for your list. 587 */ 588#define list_for_each_prev(pos, head) \ 589 for (pos = (head)->prev; pos != (head); pos = pos->prev) 590 591/** 592 * list_for_each_safe - iterate over a list safe against removal of list entry 593 * @pos: the &struct list_head to use as a loop cursor. 594 * @n: another &struct list_head to use as temporary storage 595 * @head: the head for your list. 596 */ 597#define list_for_each_safe(pos, n, head) \ 598 for (pos = (head)->next, n = pos->next; pos != (head); \ 599 pos = n, n = pos->next) 600 601/** 602 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry 603 * @pos: the &struct list_head to use as a loop cursor. 604 * @n: another &struct list_head to use as temporary storage 605 * @head: the head for your list. 606 */ 607#define list_for_each_prev_safe(pos, n, head) \ 608 for (pos = (head)->prev, n = pos->prev; \ 609 pos != (head); \ 610 pos = n, n = pos->prev) 611 612/** 613 * list_for_each_entry - iterate over list of given type 614 * @pos: the type * to use as a loop cursor. 615 * @head: the head for your list. 616 * @member: the name of the list_head within the struct. 617 */ 618#define list_for_each_entry(pos, head, member) \ 619 for (pos = list_first_entry(head, typeof(*pos), member); \ 620 &pos->member != (head); \ 621 pos = list_next_entry(pos, member)) 622 623/** 624 * list_for_each_entry_reverse - iterate backwards over list of given type. 625 * @pos: the type * to use as a loop cursor. 626 * @head: the head for your list. 627 * @member: the name of the list_head within the struct. 628 */ 629#define list_for_each_entry_reverse(pos, head, member) \ 630 for (pos = list_last_entry(head, typeof(*pos), member); \ 631 &pos->member != (head); \ 632 pos = list_prev_entry(pos, member)) 633 634/** 635 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue() 636 * @pos: the type * to use as a start point 637 * @head: the head of the list 638 * @member: the name of the list_head within the struct. 639 * 640 * Prepares a pos entry for use as a start point in list_for_each_entry_continue(). 641 */ 642#define list_prepare_entry(pos, head, member) \ 643 ((pos) ? : list_entry(head, typeof(*pos), member)) 644 645/** 646 * list_for_each_entry_continue - continue iteration over list of given type 647 * @pos: the type * to use as a loop cursor. 648 * @head: the head for your list. 649 * @member: the name of the list_head within the struct. 650 * 651 * Continue to iterate over list of given type, continuing after 652 * the current position. 653 */ 654#define list_for_each_entry_continue(pos, head, member) \ 655 for (pos = list_next_entry(pos, member); \ 656 &pos->member != (head); \ 657 pos = list_next_entry(pos, member)) 658 659/** 660 * list_for_each_entry_continue_reverse - iterate backwards from the given point 661 * @pos: the type * to use as a loop cursor. 662 * @head: the head for your list. 663 * @member: the name of the list_head within the struct. 664 * 665 * Start to iterate over list of given type backwards, continuing after 666 * the current position. 667 */ 668#define list_for_each_entry_continue_reverse(pos, head, member) \ 669 for (pos = list_prev_entry(pos, member); \ 670 &pos->member != (head); \ 671 pos = list_prev_entry(pos, member)) 672 673/** 674 * list_for_each_entry_from - iterate over list of given type from the current point 675 * @pos: the type * to use as a loop cursor. 676 * @head: the head for your list. 677 * @member: the name of the list_head within the struct. 678 * 679 * Iterate over list of given type, continuing from current position. 680 */ 681#define list_for_each_entry_from(pos, head, member) \ 682 for (; &pos->member != (head); \ 683 pos = list_next_entry(pos, member)) 684 685/** 686 * list_for_each_entry_from_reverse - iterate backwards over list of given type 687 * from the current point 688 * @pos: the type * to use as a loop cursor. 689 * @head: the head for your list. 690 * @member: the name of the list_head within the struct. 691 * 692 * Iterate backwards over list of given type, continuing from current position. 693 */ 694#define list_for_each_entry_from_reverse(pos, head, member) \ 695 for (; &pos->member != (head); \ 696 pos = list_prev_entry(pos, member)) 697 698/** 699 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry 700 * @pos: the type * to use as a loop cursor. 701 * @n: another type * to use as temporary storage 702 * @head: the head for your list. 703 * @member: the name of the list_head within the struct. 704 */ 705#define list_for_each_entry_safe(pos, n, head, member) \ 706 for (pos = list_first_entry(head, typeof(*pos), member), \ 707 n = list_next_entry(pos, member); \ 708 &pos->member != (head); \ 709 pos = n, n = list_next_entry(n, member)) 710 711/** 712 * list_for_each_entry_safe_continue - continue list iteration safe against removal 713 * @pos: the type * to use as a loop cursor. 714 * @n: another type * to use as temporary storage 715 * @head: the head for your list. 716 * @member: the name of the list_head within the struct. 717 * 718 * Iterate over list of given type, continuing after current point, 719 * safe against removal of list entry. 720 */ 721#define list_for_each_entry_safe_continue(pos, n, head, member) \ 722 for (pos = list_next_entry(pos, member), \ 723 n = list_next_entry(pos, member); \ 724 &pos->member != (head); \ 725 pos = n, n = list_next_entry(n, member)) 726 727/** 728 * list_for_each_entry_safe_from - iterate over list from current point safe against removal 729 * @pos: the type * to use as a loop cursor. 730 * @n: another type * to use as temporary storage 731 * @head: the head for your list. 732 * @member: the name of the list_head within the struct. 733 * 734 * Iterate over list of given type from current point, safe against 735 * removal of list entry. 736 */ 737#define list_for_each_entry_safe_from(pos, n, head, member) \ 738 for (n = list_next_entry(pos, member); \ 739 &pos->member != (head); \ 740 pos = n, n = list_next_entry(n, member)) 741 742/** 743 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal 744 * @pos: the type * to use as a loop cursor. 745 * @n: another type * to use as temporary storage 746 * @head: the head for your list. 747 * @member: the name of the list_head within the struct. 748 * 749 * Iterate backwards over list of given type, safe against removal 750 * of list entry. 751 */ 752#define list_for_each_entry_safe_reverse(pos, n, head, member) \ 753 for (pos = list_last_entry(head, typeof(*pos), member), \ 754 n = list_prev_entry(pos, member); \ 755 &pos->member != (head); \ 756 pos = n, n = list_prev_entry(n, member)) 757 758/** 759 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop 760 * @pos: the loop cursor used in the list_for_each_entry_safe loop 761 * @n: temporary storage used in list_for_each_entry_safe 762 * @member: the name of the list_head within the struct. 763 * 764 * list_safe_reset_next is not safe to use in general if the list may be 765 * modified concurrently (eg. the lock is dropped in the loop body). An 766 * exception to this is if the cursor element (pos) is pinned in the list, 767 * and list_safe_reset_next is called after re-taking the lock and before 768 * completing the current iteration of the loop body. 769 */ 770#define list_safe_reset_next(pos, n, member) \ 771 n = list_next_entry(pos, member) 772 773/* 774 * Double linked lists with a single pointer list head. 775 * Mostly useful for hash tables where the two pointer list head is 776 * too wasteful. 777 * You lose the ability to access the tail in O(1). 778 */ 779 780#define HLIST_HEAD_INIT { .first = NULL } 781#define HLIST_HEAD(name) struct hlist_head name = { .first = NULL } 782#define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL) 783static inline void INIT_HLIST_NODE(struct hlist_node *h) 784{ 785 h->next = NULL; 786 h->pprev = NULL; 787} 788 789/** 790 * hlist_unhashed - Has node been removed from list and reinitialized? 791 * @h: Node to be checked 792 * 793 * Not that not all removal functions will leave a node in unhashed 794 * state. For example, hlist_nulls_del_init_rcu() does leave the 795 * node in unhashed state, but hlist_nulls_del() does not. 796 */ 797static inline int hlist_unhashed(const struct hlist_node *h) 798{ 799 return !h->pprev; 800} 801 802/** 803 * hlist_unhashed_lockless - Version of hlist_unhashed for lockless use 804 * @h: Node to be checked 805 * 806 * This variant of hlist_unhashed() must be used in lockless contexts 807 * to avoid potential load-tearing. The READ_ONCE() is paired with the 808 * various WRITE_ONCE() in hlist helpers that are defined below. 809 */ 810static inline int hlist_unhashed_lockless(const struct hlist_node *h) 811{ 812 return !READ_ONCE(h->pprev); 813} 814 815/** 816 * hlist_empty - Is the specified hlist_head structure an empty hlist? 817 * @h: Structure to check. 818 */ 819static inline int hlist_empty(const struct hlist_head *h) 820{ 821 return !READ_ONCE(h->first); 822} 823 824static inline void __hlist_del(struct hlist_node *n) 825{ 826 struct hlist_node *next = n->next; 827 struct hlist_node **pprev = n->pprev; 828 829 WRITE_ONCE(*pprev, next); 830 if (next) 831 WRITE_ONCE(next->pprev, pprev); 832} 833 834/** 835 * hlist_del - Delete the specified hlist_node from its list 836 * @n: Node to delete. 837 * 838 * Note that this function leaves the node in hashed state. Use 839 * hlist_del_init() or similar instead to unhash @n. 840 */ 841static inline void hlist_del(struct hlist_node *n) 842{ 843 __hlist_del(n); 844 n->next = LIST_POISON1; 845 n->pprev = LIST_POISON2; 846} 847 848/** 849 * hlist_del_init - Delete the specified hlist_node from its list and initialize 850 * @n: Node to delete. 851 * 852 * Note that this function leaves the node in unhashed state. 853 */ 854static inline void hlist_del_init(struct hlist_node *n) 855{ 856 if (!hlist_unhashed(n)) { 857 __hlist_del(n); 858 INIT_HLIST_NODE(n); 859 } 860} 861 862/** 863 * hlist_add_head - add a new entry at the beginning of the hlist 864 * @n: new entry to be added 865 * @h: hlist head to add it after 866 * 867 * Insert a new entry after the specified head. 868 * This is good for implementing stacks. 869 */ 870static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h) 871{ 872 struct hlist_node *first = h->first; 873 WRITE_ONCE(n->next, first); 874 if (first) 875 WRITE_ONCE(first->pprev, &n->next); 876 WRITE_ONCE(h->first, n); 877 WRITE_ONCE(n->pprev, &h->first); 878} 879 880/** 881 * hlist_add_before - add a new entry before the one specified 882 * @n: new entry to be added 883 * @next: hlist node to add it before, which must be non-NULL 884 */ 885static inline void hlist_add_before(struct hlist_node *n, 886 struct hlist_node *next) 887{ 888 WRITE_ONCE(n->pprev, next->pprev); 889 WRITE_ONCE(n->next, next); 890 WRITE_ONCE(next->pprev, &n->next); 891 WRITE_ONCE(*(n->pprev), n); 892} 893 894/** 895 * hlist_add_behing - add a new entry after the one specified 896 * @n: new entry to be added 897 * @prev: hlist node to add it after, which must be non-NULL 898 */ 899static inline void hlist_add_behind(struct hlist_node *n, 900 struct hlist_node *prev) 901{ 902 WRITE_ONCE(n->next, prev->next); 903 WRITE_ONCE(prev->next, n); 904 WRITE_ONCE(n->pprev, &prev->next); 905 906 if (n->next) 907 WRITE_ONCE(n->next->pprev, &n->next); 908} 909 910/** 911 * hlist_add_fake - create a fake hlist consisting of a single headless node 912 * @n: Node to make a fake list out of 913 * 914 * This makes @n appear to be its own predecessor on a headless hlist. 915 * The point of this is to allow things like hlist_del() to work correctly 916 * in cases where there is no list. 917 */ 918static inline void hlist_add_fake(struct hlist_node *n) 919{ 920 n->pprev = &n->next; 921} 922 923/** 924 * hlist_fake: Is this node a fake hlist? 925 * @h: Node to check for being a self-referential fake hlist. 926 */ 927static inline bool hlist_fake(struct hlist_node *h) 928{ 929 return h->pprev == &h->next; 930} 931 932/** 933 * hlist_is_singular_node - is node the only element of the specified hlist? 934 * @n: Node to check for singularity. 935 * @h: Header for potentially singular list. 936 * 937 * Check whether the node is the only node of the head without 938 * accessing head, thus avoiding unnecessary cache misses. 939 */ 940static inline bool 941hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h) 942{ 943 return !n->next && n->pprev == &h->first; 944} 945 946/** 947 * hlist_move_list - Move an hlist 948 * @old: hlist_head for old list. 949 * @new: hlist_head for new list. 950 * 951 * Move a list from one list head to another. Fixup the pprev 952 * reference of the first entry if it exists. 953 */ 954static inline void hlist_move_list(struct hlist_head *old, 955 struct hlist_head *new) 956{ 957 new->first = old->first; 958 if (new->first) 959 new->first->pprev = &new->first; 960 old->first = NULL; 961} 962 963#define hlist_entry(ptr, type, member) container_of(ptr,type,member) 964 965#define hlist_for_each(pos, head) \ 966 for (pos = (head)->first; pos ; pos = pos->next) 967 968#define hlist_for_each_safe(pos, n, head) \ 969 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \ 970 pos = n) 971 972#define hlist_entry_safe(ptr, type, member) \ 973 ({ typeof(ptr) ____ptr = (ptr); \ 974 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \ 975 }) 976 977/** 978 * hlist_for_each_entry - iterate over list of given type 979 * @pos: the type * to use as a loop cursor. 980 * @head: the head for your list. 981 * @member: the name of the hlist_node within the struct. 982 */ 983#define hlist_for_each_entry(pos, head, member) \ 984 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\ 985 pos; \ 986 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member)) 987 988/** 989 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point 990 * @pos: the type * to use as a loop cursor. 991 * @member: the name of the hlist_node within the struct. 992 */ 993#define hlist_for_each_entry_continue(pos, member) \ 994 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\ 995 pos; \ 996 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member)) 997 998/** 999 * hlist_for_each_entry_from - iterate over a hlist continuing from current point 1000 * @pos: the type * to use as a loop cursor.
1001 * @member: the name of the hlist_node within the struct. 1002 */ 1003#define hlist_for_each_entry_from(pos, member) \ 1004 for (; pos; \ 1005 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member)) 1006 1007/** 1008 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry 1009 * @pos: the type * to use as a loop cursor. 1010 * @n: a &struct hlist_node to use as temporary storage 1011 * @head: the head for your list. 1012 * @member: the name of the hlist_node within the struct. 1013 */ 1014#define hlist_for_each_entry_safe(pos, n, head, member) \ 1015 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\ 1016 pos && ({ n = pos->member.next; 1; }); \ 1017 pos = hlist_entry_safe(n, typeof(*pos), member)) 1018 1019#endif 1020