1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _LINUX_LIST_H 3 #define _LINUX_LIST_H 4 5 #include <linux/container_of.h> 6 #include <linux/types.h> 7 #include <linux/stddef.h> 8 #include <linux/poison.h> 9 #include <linux/const.h> 10 11 #include <asm/barrier.h> 12 13 /* 14 * Circular doubly linked list implementation. 15 * 16 * Some of the internal functions ("__xxx") are useful when 17 * manipulating whole lists rather than single entries, as 18 * sometimes we already know the next/prev entries and we can 19 * generate better code by using them directly rather than 20 * using the generic single-entry routines. 21 */ 22 23 #define LIST_HEAD_INIT(name) { &(name), &(name) } 24 25 #define LIST_HEAD(name) \ 26 struct list_head name = LIST_HEAD_INIT(name) 27 28 /** 29 * INIT_LIST_HEAD - Initialize a list_head structure 30 * @list: list_head structure to be initialized. 31 * 32 * Initializes the list_head to point to itself. If it is a list header, 33 * the result is an empty list. 34 */ 35 static inline void INIT_LIST_HEAD(struct list_head *list) 36 { 37 WRITE_ONCE(list->next, list); 38 WRITE_ONCE(list->prev, list); 39 } 40 41 #ifdef CONFIG_DEBUG_LIST 42 extern bool __list_add_valid(struct list_head *new, 43 struct list_head *prev, 44 struct list_head *next); 45 extern bool __list_del_entry_valid(struct list_head *entry); 46 #else 47 static inline bool __list_add_valid(struct list_head *new, 48 struct list_head *prev, 49 struct list_head *next) 50 { 51 return true; 52 } 53 static inline bool __list_del_entry_valid(struct list_head *entry) 54 { 55 return true; 56 } 57 #endif 58 59 /* 60 * Insert a new entry between two known consecutive entries. 61 * 62 * This is only for internal list manipulation where we know 63 * the prev/next entries already! 64 */ 65 static inline void __list_add(struct list_head *new, 66 struct list_head *prev, 67 struct list_head *next) 68 { 69 if (!__list_add_valid(new, prev, next)) 70 return; 71 72 next->prev = new; 73 new->next = next; 74 new->prev = prev; 75 WRITE_ONCE(prev->next, new); 76 } 77 78 /** 79 * list_add - add a new entry 80 * @new: new entry to be added 81 * @head: list head to add it after 82 * 83 * Insert a new entry after the specified head. 84 * This is good for implementing stacks. 85 */ 86 static inline void list_add(struct list_head *new, struct list_head *head) 87 { 88 __list_add(new, head, head->next); 89 } 90 91 92 /** 93 * list_add_tail - add a new entry 94 * @new: new entry to be added 95 * @head: list head to add it before 96 * 97 * Insert a new entry before the specified head. 98 * This is useful for implementing queues. 99 */ 100 static inline void list_add_tail(struct list_head *new, struct list_head *head) 101 { 102 __list_add(new, head->prev, head); 103 } 104 105 /* 106 * Delete a list entry by making the prev/next entries 107 * point to each other. 108 * 109 * This is only for internal list manipulation where we know 110 * the prev/next entries already! 111 */ 112 static inline void __list_del(struct list_head * prev, struct list_head * next) 113 { 114 next->prev = prev; 115 WRITE_ONCE(prev->next, next); 116 } 117 118 /* 119 * Delete a list entry and clear the 'prev' pointer. 120 * 121 * This is a special-purpose list clearing method used in the networking code 122 * for lists allocated as per-cpu, where we don't want to incur the extra 123 * WRITE_ONCE() overhead of a regular list_del_init(). The code that uses this 124 * needs to check the node 'prev' pointer instead of calling list_empty(). 125 */ 126 static inline void __list_del_clearprev(struct list_head *entry) 127 { 128 __list_del(entry->prev, entry->next); 129 entry->prev = NULL; 130 } 131 132 static inline void __list_del_entry(struct list_head *entry) 133 { 134 if (!__list_del_entry_valid(entry)) 135 return; 136 137 __list_del(entry->prev, entry->next); 138 } 139 140 /** 141 * list_del - deletes entry from list. 142 * @entry: the element to delete from the list. 143 * Note: list_empty() on entry does not return true after this, the entry is 144 * in an undefined state. 145 */ 146 static inline void list_del(struct list_head *entry) 147 { 148 __list_del_entry(entry); 149 entry->next = LIST_POISON1; 150 entry->prev = LIST_POISON2; 151 } 152 153 /** 154 * list_replace - replace old entry by new one 155 * @old : the element to be replaced 156 * @new : the new element to insert 157 * 158 * If @old was empty, it will be overwritten. 159 */ 160 static inline void list_replace(struct list_head *old, 161 struct list_head *new) 162 { 163 new->next = old->next; 164 new->next->prev = new; 165 new->prev = old->prev; 166 new->prev->next = new; 167 } 168 169 /** 170 * list_replace_init - replace old entry by new one and initialize the old one 171 * @old : the element to be replaced 172 * @new : the new element to insert 173 * 174 * If @old was empty, it will be overwritten. 175 */ 176 static inline void list_replace_init(struct list_head *old, 177 struct list_head *new) 178 { 179 list_replace(old, new); 180 INIT_LIST_HEAD(old); 181 } 182 183 /** 184 * list_swap - replace entry1 with entry2 and re-add entry1 at entry2's position 185 * @entry1: the location to place entry2 186 * @entry2: the location to place entry1 187 */ 188 static inline void list_swap(struct list_head *entry1, 189 struct list_head *entry2) 190 { 191 struct list_head *pos = entry2->prev; 192 193 list_del(entry2); 194 list_replace(entry1, entry2); 195 if (pos == entry1) 196 pos = entry2; 197 list_add(entry1, pos); 198 } 199 200 /** 201 * list_del_init - deletes entry from list and reinitialize it. 202 * @entry: the element to delete from the list. 203 */ 204 static inline void list_del_init(struct list_head *entry) 205 { 206 __list_del_entry(entry); 207 INIT_LIST_HEAD(entry); 208 } 209 210 /** 211 * list_move - delete from one list and add as another's head 212 * @list: the entry to move 213 * @head: the head that will precede our entry 214 */ 215 static inline void list_move(struct list_head *list, struct list_head *head) 216 { 217 __list_del_entry(list); 218 list_add(list, head); 219 } 220 221 /** 222 * list_move_tail - delete from one list and add as another's tail 223 * @list: the entry to move 224 * @head: the head that will follow our entry 225 */ 226 static inline void list_move_tail(struct list_head *list, 227 struct list_head *head) 228 { 229 __list_del_entry(list); 230 list_add_tail(list, head); 231 } 232 233 /** 234 * list_bulk_move_tail - move a subsection of a list to its tail 235 * @head: the head that will follow our entry 236 * @first: first entry to move 237 * @last: last entry to move, can be the same as first 238 * 239 * Move all entries between @first and including @last before @head. 240 * All three entries must belong to the same linked list. 241 */ 242 static inline void list_bulk_move_tail(struct list_head *head, 243 struct list_head *first, 244 struct list_head *last) 245 { 246 first->prev->next = last->next; 247 last->next->prev = first->prev; 248 249 head->prev->next = first; 250 first->prev = head->prev; 251 252 last->next = head; 253 head->prev = last; 254 } 255 256 /** 257 * list_is_first -- tests whether @list is the first entry in list @head 258 * @list: the entry to test 259 * @head: the head of the list 260 */ 261 static inline int list_is_first(const struct list_head *list, const struct list_head *head) 262 { 263 return list->prev == head; 264 } 265 266 /** 267 * list_is_last - tests whether @list is the last entry in list @head 268 * @list: the entry to test 269 * @head: the head of the list 270 */ 271 static inline int list_is_last(const struct list_head *list, const struct list_head *head) 272 { 273 return list->next == head; 274 } 275 276 /** 277 * list_is_head - tests whether @list is the list @head 278 * @list: the entry to test 279 * @head: the head of the list 280 */ 281 static inline int list_is_head(const struct list_head *list, const struct list_head *head) 282 { 283 return list == head; 284 } 285 286 /** 287 * list_empty - tests whether a list is empty 288 * @head: the list to test. 289 */ 290 static inline int list_empty(const struct list_head *head) 291 { 292 return READ_ONCE(head->next) == head; 293 } 294 295 /** 296 * list_del_init_careful - deletes entry from list and reinitialize it. 297 * @entry: the element to delete from the list. 298 * 299 * This is the same as list_del_init(), except designed to be used 300 * together with list_empty_careful() in a way to guarantee ordering 301 * of other memory operations. 302 * 303 * Any memory operations done before a list_del_init_careful() are 304 * guaranteed to be visible after a list_empty_careful() test. 305 */ 306 static inline void list_del_init_careful(struct list_head *entry) 307 { 308 __list_del_entry(entry); 309 WRITE_ONCE(entry->prev, entry); 310 smp_store_release(&entry->next, entry); 311 } 312 313 /** 314 * list_empty_careful - tests whether a list is empty and not being modified 315 * @head: the list to test 316 * 317 * Description: 318 * tests whether a list is empty _and_ checks that no other CPU might be 319 * in the process of modifying either member (next or prev) 320 * 321 * NOTE: using list_empty_careful() without synchronization 322 * can only be safe if the only activity that can happen 323 * to the list entry is list_del_init(). Eg. it cannot be used 324 * if another CPU could re-list_add() it. 325 */ 326 static inline int list_empty_careful(const struct list_head *head) 327 { 328 struct list_head *next = smp_load_acquire(&head->next); 329 return list_is_head(next, head) && (next == READ_ONCE(head->prev)); 330 } 331 332 /** 333 * list_rotate_left - rotate the list to the left 334 * @head: the head of the list 335 */ 336 static inline void list_rotate_left(struct list_head *head) 337 { 338 struct list_head *first; 339 340 if (!list_empty(head)) { 341 first = head->next; 342 list_move_tail(first, head); 343 } 344 } 345 346 /** 347 * list_rotate_to_front() - Rotate list to specific item. 348 * @list: The desired new front of the list. 349 * @head: The head of the list. 350 * 351 * Rotates list so that @list becomes the new front of the list. 352 */ 353 static inline void list_rotate_to_front(struct list_head *list, 354 struct list_head *head) 355 { 356 /* 357 * Deletes the list head from the list denoted by @head and 358 * places it as the tail of @list, this effectively rotates the 359 * list so that @list is at the front. 360 */ 361 list_move_tail(head, list); 362 } 363 364 /** 365 * list_is_singular - tests whether a list has just one entry. 366 * @head: the list to test. 367 */ 368 static inline int list_is_singular(const struct list_head *head) 369 { 370 return !list_empty(head) && (head->next == head->prev); 371 } 372 373 static inline void __list_cut_position(struct list_head *list, 374 struct list_head *head, struct list_head *entry) 375 { 376 struct list_head *new_first = entry->next; 377 list->next = head->next; 378 list->next->prev = list; 379 list->prev = entry; 380 entry->next = list; 381 head->next = new_first; 382 new_first->prev = head; 383 } 384 385 /** 386 * list_cut_position - cut a list into two 387 * @list: a new list to add all removed entries 388 * @head: a list with entries 389 * @entry: an entry within head, could be the head itself 390 * and if so we won't cut the list 391 * 392 * This helper moves the initial part of @head, up to and 393 * including @entry, from @head to @list. You should 394 * pass on @entry an element you know is on @head. @list 395 * should be an empty list or a list you do not care about 396 * losing its data. 397 * 398 */ 399 static inline void list_cut_position(struct list_head *list, 400 struct list_head *head, struct list_head *entry) 401 { 402 if (list_empty(head)) 403 return; 404 if (list_is_singular(head) && !list_is_head(entry, head) && (entry != head->next)) 405 return; 406 if (list_is_head(entry, head)) 407 INIT_LIST_HEAD(list); 408 else 409 __list_cut_position(list, head, entry); 410 } 411 412 /** 413 * list_cut_before - cut a list into two, before given entry 414 * @list: a new list to add all removed entries 415 * @head: a list with entries 416 * @entry: an entry within head, could be the head itself 417 * 418 * This helper moves the initial part of @head, up to but 419 * excluding @entry, from @head to @list. You should pass 420 * in @entry an element you know is on @head. @list should 421 * be an empty list or a list you do not care about losing 422 * its data. 423 * If @entry == @head, all entries on @head are moved to 424 * @list. 425 */ 426 static inline void list_cut_before(struct list_head *list, 427 struct list_head *head, 428 struct list_head *entry) 429 { 430 if (head->next == entry) { 431 INIT_LIST_HEAD(list); 432 return; 433 } 434 list->next = head->next; 435 list->next->prev = list; 436 list->prev = entry->prev; 437 list->prev->next = list; 438 head->next = entry; 439 entry->prev = head; 440 } 441 442 static inline void __list_splice(const struct list_head *list, 443 struct list_head *prev, 444 struct list_head *next) 445 { 446 struct list_head *first = list->next; 447 struct list_head *last = list->prev; 448 449 first->prev = prev; 450 prev->next = first; 451 452 last->next = next; 453 next->prev = last; 454 } 455 456 /** 457 * list_splice - join two lists, this is designed for stacks 458 * @list: the new list to add. 459 * @head: the place to add it in the first list. 460 */ 461 static inline void list_splice(const struct list_head *list, 462 struct list_head *head) 463 { 464 if (!list_empty(list)) 465 __list_splice(list, head, head->next); 466 } 467 468 /** 469 * list_splice_tail - join two lists, each list being a queue 470 * @list: the new list to add. 471 * @head: the place to add it in the first list. 472 */ 473 static inline void list_splice_tail(struct list_head *list, 474 struct list_head *head) 475 { 476 if (!list_empty(list)) 477 __list_splice(list, head->prev, head); 478 } 479 480 /** 481 * list_splice_init - join two lists and reinitialise the emptied list. 482 * @list: the new list to add. 483 * @head: the place to add it in the first list. 484 * 485 * The list at @list is reinitialised 486 */ 487 static inline void list_splice_init(struct list_head *list, 488 struct list_head *head) 489 { 490 if (!list_empty(list)) { 491 __list_splice(list, head, head->next); 492 INIT_LIST_HEAD(list); 493 } 494 } 495 496 /** 497 * list_splice_tail_init - join two lists and reinitialise the emptied list 498 * @list: the new list to add. 499 * @head: the place to add it in the first list. 500 * 501 * Each of the lists is a queue. 502 * The list at @list is reinitialised 503 */ 504 static inline void list_splice_tail_init(struct list_head *list, 505 struct list_head *head) 506 { 507 if (!list_empty(list)) { 508 __list_splice(list, head->prev, head); 509 INIT_LIST_HEAD(list); 510 } 511 } 512 513 /** 514 * list_entry - get the struct for this entry 515 * @ptr: the &struct list_head pointer. 516 * @type: the type of the struct this is embedded in. 517 * @member: the name of the list_head within the struct. 518 */ 519 #define list_entry(ptr, type, member) \ 520 container_of(ptr, type, member) 521 522 /** 523 * list_first_entry - get the first element from a list 524 * @ptr: the list head to take the element from. 525 * @type: the type of the struct this is embedded in. 526 * @member: the name of the list_head within the struct. 527 * 528 * Note, that list is expected to be not empty. 529 */ 530 #define list_first_entry(ptr, type, member) \ 531 list_entry((ptr)->next, type, member) 532 533 /** 534 * list_last_entry - get the last element from a list 535 * @ptr: the list head to take the element from. 536 * @type: the type of the struct this is embedded in. 537 * @member: the name of the list_head within the struct. 538 * 539 * Note, that list is expected to be not empty. 540 */ 541 #define list_last_entry(ptr, type, member) \ 542 list_entry((ptr)->prev, type, member) 543 544 /** 545 * list_first_entry_or_null - get the first element from a list 546 * @ptr: the list head to take the element from. 547 * @type: the type of the struct this is embedded in. 548 * @member: the name of the list_head within the struct. 549 * 550 * Note that if the list is empty, it returns NULL. 551 */ 552 #define list_first_entry_or_null(ptr, type, member) ({ \ 553 struct list_head *head__ = (ptr); \ 554 struct list_head *pos__ = READ_ONCE(head__->next); \ 555 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \ 556 }) 557 558 /** 559 * list_next_entry - get the next element in list 560 * @pos: the type * to cursor 561 * @member: the name of the list_head within the struct. 562 */ 563 #define list_next_entry(pos, member) \ 564 list_entry((pos)->member.next, typeof(*(pos)), member) 565 566 /** 567 * list_next_entry_circular - get the next element in list 568 * @pos: the type * to cursor. 569 * @head: the list head to take the element from. 570 * @member: the name of the list_head within the struct. 571 * 572 * Wraparound if pos is the last element (return the first element). 573 * Note, that list is expected to be not empty. 574 */ 575 #define list_next_entry_circular(pos, head, member) \ 576 (list_is_last(&(pos)->member, head) ? \ 577 list_first_entry(head, typeof(*(pos)), member) : list_next_entry(pos, member)) 578 579 /** 580 * list_prev_entry - get the prev element in list 581 * @pos: the type * to cursor 582 * @member: the name of the list_head within the struct. 583 */ 584 #define list_prev_entry(pos, member) \ 585 list_entry((pos)->member.prev, typeof(*(pos)), member) 586 587 /** 588 * list_prev_entry_circular - get the prev element in list 589 * @pos: the type * to cursor. 590 * @head: the list head to take the element from. 591 * @member: the name of the list_head within the struct. 592 * 593 * Wraparound if pos is the first element (return the last element). 594 * Note, that list is expected to be not empty. 595 */ 596 #define list_prev_entry_circular(pos, head, member) \ 597 (list_is_first(&(pos)->member, head) ? \ 598 list_last_entry(head, typeof(*(pos)), member) : list_prev_entry(pos, member)) 599 600 /** 601 * list_for_each - iterate over a list 602 * @pos: the &struct list_head to use as a loop cursor. 603 * @head: the head for your list. 604 */ 605 #define list_for_each(pos, head) \ 606 for (pos = (head)->next; !list_is_head(pos, (head)); pos = pos->next) 607 608 /** 609 * list_for_each_rcu - Iterate over a list in an RCU-safe fashion 610 * @pos: the &struct list_head to use as a loop cursor. 611 * @head: the head for your list. 612 */ 613 #define list_for_each_rcu(pos, head) \ 614 for (pos = rcu_dereference((head)->next); \ 615 !list_is_head(pos, (head)); \ 616 pos = rcu_dereference(pos->next)) 617 618 /** 619 * list_for_each_continue - continue iteration over a list 620 * @pos: the &struct list_head to use as a loop cursor. 621 * @head: the head for your list. 622 * 623 * Continue to iterate over a list, continuing after the current position. 624 */ 625 #define list_for_each_continue(pos, head) \ 626 for (pos = pos->next; !list_is_head(pos, (head)); pos = pos->next) 627 628 /** 629 * list_for_each_prev - iterate over a list backwards 630 * @pos: the &struct list_head to use as a loop cursor. 631 * @head: the head for your list. 632 */ 633 #define list_for_each_prev(pos, head) \ 634 for (pos = (head)->prev; !list_is_head(pos, (head)); pos = pos->prev) 635 636 /** 637 * list_for_each_safe - iterate over a list safe against removal of list entry 638 * @pos: the &struct list_head to use as a loop cursor. 639 * @n: another &struct list_head to use as temporary storage 640 * @head: the head for your list. 641 */ 642 #define list_for_each_safe(pos, n, head) \ 643 for (pos = (head)->next, n = pos->next; \ 644 !list_is_head(pos, (head)); \ 645 pos = n, n = pos->next) 646 647 /** 648 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry 649 * @pos: the &struct list_head to use as a loop cursor. 650 * @n: another &struct list_head to use as temporary storage 651 * @head: the head for your list. 652 */ 653 #define list_for_each_prev_safe(pos, n, head) \ 654 for (pos = (head)->prev, n = pos->prev; \ 655 !list_is_head(pos, (head)); \ 656 pos = n, n = pos->prev) 657 658 /** 659 * list_count_nodes - count nodes in the list 660 * @head: the head for your list. 661 */ 662 static inline size_t list_count_nodes(struct list_head *head) 663 { 664 struct list_head *pos; 665 size_t count = 0; 666 667 list_for_each(pos, head) 668 count++; 669 670 return count; 671 } 672 673 /** 674 * list_entry_is_head - test if the entry points to the head of the list 675 * @pos: the type * to cursor 676 * @head: the head for your list. 677 * @member: the name of the list_head within the struct. 678 */ 679 #define list_entry_is_head(pos, head, member) \ 680 (&pos->member == (head)) 681 682 /** 683 * list_for_each_entry - iterate over list of given type 684 * @pos: the type * to use as a loop cursor. 685 * @head: the head for your list. 686 * @member: the name of the list_head within the struct. 687 */ 688 #define list_for_each_entry(pos, head, member) \ 689 for (pos = list_first_entry(head, typeof(*pos), member); \ 690 !list_entry_is_head(pos, head, member); \ 691 pos = list_next_entry(pos, member)) 692 693 /** 694 * list_for_each_entry_reverse - iterate backwards over list of given type. 695 * @pos: the type * to use as a loop cursor. 696 * @head: the head for your list. 697 * @member: the name of the list_head within the struct. 698 */ 699 #define list_for_each_entry_reverse(pos, head, member) \ 700 for (pos = list_last_entry(head, typeof(*pos), member); \ 701 !list_entry_is_head(pos, head, member); \ 702 pos = list_prev_entry(pos, member)) 703 704 /** 705 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue() 706 * @pos: the type * to use as a start point 707 * @head: the head of the list 708 * @member: the name of the list_head within the struct. 709 * 710 * Prepares a pos entry for use as a start point in list_for_each_entry_continue(). 711 */ 712 #define list_prepare_entry(pos, head, member) \ 713 ((pos) ? : list_entry(head, typeof(*pos), member)) 714 715 /** 716 * list_for_each_entry_continue - continue iteration over list of given type 717 * @pos: the type * to use as a loop cursor. 718 * @head: the head for your list. 719 * @member: the name of the list_head within the struct. 720 * 721 * Continue to iterate over list of given type, continuing after 722 * the current position. 723 */ 724 #define list_for_each_entry_continue(pos, head, member) \ 725 for (pos = list_next_entry(pos, member); \ 726 !list_entry_is_head(pos, head, member); \ 727 pos = list_next_entry(pos, member)) 728 729 /** 730 * list_for_each_entry_continue_reverse - iterate backwards from the given point 731 * @pos: the type * to use as a loop cursor. 732 * @head: the head for your list. 733 * @member: the name of the list_head within the struct. 734 * 735 * Start to iterate over list of given type backwards, continuing after 736 * the current position. 737 */ 738 #define list_for_each_entry_continue_reverse(pos, head, member) \ 739 for (pos = list_prev_entry(pos, member); \ 740 !list_entry_is_head(pos, head, member); \ 741 pos = list_prev_entry(pos, member)) 742 743 /** 744 * list_for_each_entry_from - iterate over list of given type from the current point 745 * @pos: the type * to use as a loop cursor. 746 * @head: the head for your list. 747 * @member: the name of the list_head within the struct. 748 * 749 * Iterate over list of given type, continuing from current position. 750 */ 751 #define list_for_each_entry_from(pos, head, member) \ 752 for (; !list_entry_is_head(pos, head, member); \ 753 pos = list_next_entry(pos, member)) 754 755 /** 756 * list_for_each_entry_from_reverse - iterate backwards over list of given type 757 * from the current point 758 * @pos: the type * to use as a loop cursor. 759 * @head: the head for your list. 760 * @member: the name of the list_head within the struct. 761 * 762 * Iterate backwards over list of given type, continuing from current position. 763 */ 764 #define list_for_each_entry_from_reverse(pos, head, member) \ 765 for (; !list_entry_is_head(pos, head, member); \ 766 pos = list_prev_entry(pos, member)) 767 768 /** 769 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry 770 * @pos: the type * to use as a loop cursor. 771 * @n: another type * to use as temporary storage 772 * @head: the head for your list. 773 * @member: the name of the list_head within the struct. 774 */ 775 #define list_for_each_entry_safe(pos, n, head, member) \ 776 for (pos = list_first_entry(head, typeof(*pos), member), \ 777 n = list_next_entry(pos, member); \ 778 !list_entry_is_head(pos, head, member); \ 779 pos = n, n = list_next_entry(n, member)) 780 781 /** 782 * list_for_each_entry_safe_continue - continue list iteration safe against removal 783 * @pos: the type * to use as a loop cursor. 784 * @n: another type * to use as temporary storage 785 * @head: the head for your list. 786 * @member: the name of the list_head within the struct. 787 * 788 * Iterate over list of given type, continuing after current point, 789 * safe against removal of list entry. 790 */ 791 #define list_for_each_entry_safe_continue(pos, n, head, member) \ 792 for (pos = list_next_entry(pos, member), \ 793 n = list_next_entry(pos, member); \ 794 !list_entry_is_head(pos, head, member); \ 795 pos = n, n = list_next_entry(n, member)) 796 797 /** 798 * list_for_each_entry_safe_from - iterate over list from current point safe against removal 799 * @pos: the type * to use as a loop cursor. 800 * @n: another type * to use as temporary storage 801 * @head: the head for your list. 802 * @member: the name of the list_head within the struct. 803 * 804 * Iterate over list of given type from current point, safe against 805 * removal of list entry. 806 */ 807 #define list_for_each_entry_safe_from(pos, n, head, member) \ 808 for (n = list_next_entry(pos, member); \ 809 !list_entry_is_head(pos, head, member); \ 810 pos = n, n = list_next_entry(n, member)) 811 812 /** 813 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal 814 * @pos: the type * to use as a loop cursor. 815 * @n: another type * to use as temporary storage 816 * @head: the head for your list. 817 * @member: the name of the list_head within the struct. 818 * 819 * Iterate backwards over list of given type, safe against removal 820 * of list entry. 821 */ 822 #define list_for_each_entry_safe_reverse(pos, n, head, member) \ 823 for (pos = list_last_entry(head, typeof(*pos), member), \ 824 n = list_prev_entry(pos, member); \ 825 !list_entry_is_head(pos, head, member); \ 826 pos = n, n = list_prev_entry(n, member)) 827 828 /** 829 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop 830 * @pos: the loop cursor used in the list_for_each_entry_safe loop 831 * @n: temporary storage used in list_for_each_entry_safe 832 * @member: the name of the list_head within the struct. 833 * 834 * list_safe_reset_next is not safe to use in general if the list may be 835 * modified concurrently (eg. the lock is dropped in the loop body). An 836 * exception to this is if the cursor element (pos) is pinned in the list, 837 * and list_safe_reset_next is called after re-taking the lock and before 838 * completing the current iteration of the loop body. 839 */ 840 #define list_safe_reset_next(pos, n, member) \ 841 n = list_next_entry(pos, member) 842 843 /* 844 * Double linked lists with a single pointer list head. 845 * Mostly useful for hash tables where the two pointer list head is 846 * too wasteful. 847 * You lose the ability to access the tail in O(1). 848 */ 849 850 #define HLIST_HEAD_INIT { .first = NULL } 851 #define HLIST_HEAD(name) struct hlist_head name = { .first = NULL } 852 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL) 853 static inline void INIT_HLIST_NODE(struct hlist_node *h) 854 { 855 h->next = NULL; 856 h->pprev = NULL; 857 } 858 859 /** 860 * hlist_unhashed - Has node been removed from list and reinitialized? 861 * @h: Node to be checked 862 * 863 * Not that not all removal functions will leave a node in unhashed 864 * state. For example, hlist_nulls_del_init_rcu() does leave the 865 * node in unhashed state, but hlist_nulls_del() does not. 866 */ 867 static inline int hlist_unhashed(const struct hlist_node *h) 868 { 869 return !h->pprev; 870 } 871 872 /** 873 * hlist_unhashed_lockless - Version of hlist_unhashed for lockless use 874 * @h: Node to be checked 875 * 876 * This variant of hlist_unhashed() must be used in lockless contexts 877 * to avoid potential load-tearing. The READ_ONCE() is paired with the 878 * various WRITE_ONCE() in hlist helpers that are defined below. 879 */ 880 static inline int hlist_unhashed_lockless(const struct hlist_node *h) 881 { 882 return !READ_ONCE(h->pprev); 883 } 884 885 /** 886 * hlist_empty - Is the specified hlist_head structure an empty hlist? 887 * @h: Structure to check. 888 */ 889 static inline int hlist_empty(const struct hlist_head *h) 890 { 891 return !READ_ONCE(h->first); 892 } 893 894 static inline void __hlist_del(struct hlist_node *n) 895 { 896 struct hlist_node *next = n->next; 897 struct hlist_node **pprev = n->pprev; 898 899 WRITE_ONCE(*pprev, next); 900 if (next) 901 WRITE_ONCE(next->pprev, pprev); 902 } 903 904 /** 905 * hlist_del - Delete the specified hlist_node from its list 906 * @n: Node to delete. 907 * 908 * Note that this function leaves the node in hashed state. Use 909 * hlist_del_init() or similar instead to unhash @n. 910 */ 911 static inline void hlist_del(struct hlist_node *n) 912 { 913 __hlist_del(n); 914 n->next = LIST_POISON1; 915 n->pprev = LIST_POISON2; 916 } 917 918 /** 919 * hlist_del_init - Delete the specified hlist_node from its list and initialize 920 * @n: Node to delete. 921 * 922 * Note that this function leaves the node in unhashed state. 923 */ 924 static inline void hlist_del_init(struct hlist_node *n) 925 { 926 if (!hlist_unhashed(n)) { 927 __hlist_del(n); 928 INIT_HLIST_NODE(n); 929 } 930 } 931 932 /** 933 * hlist_add_head - add a new entry at the beginning of the hlist 934 * @n: new entry to be added 935 * @h: hlist head to add it after 936 * 937 * Insert a new entry after the specified head. 938 * This is good for implementing stacks. 939 */ 940 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h) 941 { 942 struct hlist_node *first = h->first; 943 WRITE_ONCE(n->next, first); 944 if (first) 945 WRITE_ONCE(first->pprev, &n->next); 946 WRITE_ONCE(h->first, n); 947 WRITE_ONCE(n->pprev, &h->first); 948 } 949 950 /** 951 * hlist_add_before - add a new entry before the one specified 952 * @n: new entry to be added 953 * @next: hlist node to add it before, which must be non-NULL 954 */ 955 static inline void hlist_add_before(struct hlist_node *n, 956 struct hlist_node *next) 957 { 958 WRITE_ONCE(n->pprev, next->pprev); 959 WRITE_ONCE(n->next, next); 960 WRITE_ONCE(next->pprev, &n->next); 961 WRITE_ONCE(*(n->pprev), n); 962 } 963 964 /** 965 * hlist_add_behind - add a new entry after the one specified 966 * @n: new entry to be added 967 * @prev: hlist node to add it after, which must be non-NULL 968 */ 969 static inline void hlist_add_behind(struct hlist_node *n, 970 struct hlist_node *prev) 971 { 972 WRITE_ONCE(n->next, prev->next); 973 WRITE_ONCE(prev->next, n); 974 WRITE_ONCE(n->pprev, &prev->next); 975 976 if (n->next) 977 WRITE_ONCE(n->next->pprev, &n->next); 978 } 979 980 /** 981 * hlist_add_fake - create a fake hlist consisting of a single headless node 982 * @n: Node to make a fake list out of 983 * 984 * This makes @n appear to be its own predecessor on a headless hlist. 985 * The point of this is to allow things like hlist_del() to work correctly 986 * in cases where there is no list. 987 */ 988 static inline void hlist_add_fake(struct hlist_node *n) 989 { 990 n->pprev = &n->next; 991 } 992 993 /** 994 * hlist_fake: Is this node a fake hlist? 995 * @h: Node to check for being a self-referential fake hlist. 996 */ 997 static inline bool hlist_fake(struct hlist_node *h) 998 { 999 return h->pprev == &h->next; 1000 } 1001 1002 /** 1003 * hlist_is_singular_node - is node the only element of the specified hlist? 1004 * @n: Node to check for singularity. 1005 * @h: Header for potentially singular list. 1006 * 1007 * Check whether the node is the only node of the head without 1008 * accessing head, thus avoiding unnecessary cache misses. 1009 */ 1010 static inline bool 1011 hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h) 1012 { 1013 return !n->next && n->pprev == &h->first; 1014 } 1015 1016 /** 1017 * hlist_move_list - Move an hlist 1018 * @old: hlist_head for old list. 1019 * @new: hlist_head for new list. 1020 * 1021 * Move a list from one list head to another. Fixup the pprev 1022 * reference of the first entry if it exists. 1023 */ 1024 static inline void hlist_move_list(struct hlist_head *old, 1025 struct hlist_head *new) 1026 { 1027 new->first = old->first; 1028 if (new->first) 1029 new->first->pprev = &new->first; 1030 old->first = NULL; 1031 } 1032 1033 #define hlist_entry(ptr, type, member) container_of(ptr,type,member) 1034 1035 #define hlist_for_each(pos, head) \ 1036 for (pos = (head)->first; pos ; pos = pos->next) 1037 1038 #define hlist_for_each_safe(pos, n, head) \ 1039 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \ 1040 pos = n) 1041 1042 #define hlist_entry_safe(ptr, type, member) \ 1043 ({ typeof(ptr) ____ptr = (ptr); \ 1044 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \ 1045 }) 1046 1047 /** 1048 * hlist_for_each_entry - iterate over list of given type 1049 * @pos: the type * to use as a loop cursor. 1050 * @head: the head for your list. 1051 * @member: the name of the hlist_node within the struct. 1052 */ 1053 #define hlist_for_each_entry(pos, head, member) \ 1054 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\ 1055 pos; \ 1056 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member)) 1057 1058 /** 1059 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point 1060 * @pos: the type * to use as a loop cursor. 1061 * @member: the name of the hlist_node within the struct. 1062 */ 1063 #define hlist_for_each_entry_continue(pos, member) \ 1064 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\ 1065 pos; \ 1066 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member)) 1067 1068 /** 1069 * hlist_for_each_entry_from - iterate over a hlist continuing from current point 1070 * @pos: the type * to use as a loop cursor. 1071 * @member: the name of the hlist_node within the struct. 1072 */ 1073 #define hlist_for_each_entry_from(pos, member) \ 1074 for (; pos; \ 1075 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member)) 1076 1077 /** 1078 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry 1079 * @pos: the type * to use as a loop cursor. 1080 * @n: a &struct hlist_node to use as temporary storage 1081 * @head: the head for your list. 1082 * @member: the name of the hlist_node within the struct. 1083 */ 1084 #define hlist_for_each_entry_safe(pos, n, head, member) \ 1085 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\ 1086 pos && ({ n = pos->member.next; 1; }); \ 1087 pos = hlist_entry_safe(n, typeof(*pos), member)) 1088 1089 #endif 1090