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 */ 33 static 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 40 extern bool __list_add_valid(struct list_head *new, 41 struct list_head *prev, 42 struct list_head *next); 43 extern bool __list_del_entry_valid(struct list_head *entry); 44 #else 45 static inline bool __list_add_valid(struct list_head *new, 46 struct list_head *prev, 47 struct list_head *next) 48 { 49 return true; 50 } 51 static 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 */ 63 static 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 */ 84 static 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 */ 98 static 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 */ 110 static 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 */ 124 static inline void __list_del_clearprev(struct list_head *entry) 125 { 126 __list_del(entry->prev, entry->next); 127 entry->prev = NULL; 128 } 129 130 static 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 */ 144 static 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 */ 158 static 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 */ 174 static 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 */ 186 static 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 */ 202 static 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 */ 213 static 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 */ 224 static 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 */ 240 static 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 */ 259 static 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 */ 270 static 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 */ 280 static inline int list_empty(const struct list_head *head) 281 { 282 return READ_ONCE(head->next) == head; 283 } 284 285 /** 286 * list_empty_careful - tests whether a list is empty and not being modified 287 * @head: the list to test 288 * 289 * Description: 290 * tests whether a list is empty _and_ checks that no other CPU might be 291 * in the process of modifying either member (next or prev) 292 * 293 * NOTE: using list_empty_careful() without synchronization 294 * can only be safe if the only activity that can happen 295 * to the list entry is list_del_init(). Eg. it cannot be used 296 * if another CPU could re-list_add() it. 297 */ 298 static inline int list_empty_careful(const struct list_head *head) 299 { 300 struct list_head *next = head->next; 301 return (next == head) && (next == head->prev); 302 } 303 304 /** 305 * list_rotate_left - rotate the list to the left 306 * @head: the head of the list 307 */ 308 static inline void list_rotate_left(struct list_head *head) 309 { 310 struct list_head *first; 311 312 if (!list_empty(head)) { 313 first = head->next; 314 list_move_tail(first, head); 315 } 316 } 317 318 /** 319 * list_rotate_to_front() - Rotate list to specific item. 320 * @list: The desired new front of the list. 321 * @head: The head of the list. 322 * 323 * Rotates list so that @list becomes the new front of the list. 324 */ 325 static inline void list_rotate_to_front(struct list_head *list, 326 struct list_head *head) 327 { 328 /* 329 * Deletes the list head from the list denoted by @head and 330 * places it as the tail of @list, this effectively rotates the 331 * list so that @list is at the front. 332 */ 333 list_move_tail(head, list); 334 } 335 336 /** 337 * list_is_singular - tests whether a list has just one entry. 338 * @head: the list to test. 339 */ 340 static inline int list_is_singular(const struct list_head *head) 341 { 342 return !list_empty(head) && (head->next == head->prev); 343 } 344 345 static inline void __list_cut_position(struct list_head *list, 346 struct list_head *head, struct list_head *entry) 347 { 348 struct list_head *new_first = entry->next; 349 list->next = head->next; 350 list->next->prev = list; 351 list->prev = entry; 352 entry->next = list; 353 head->next = new_first; 354 new_first->prev = head; 355 } 356 357 /** 358 * list_cut_position - cut a list into two 359 * @list: a new list to add all removed entries 360 * @head: a list with entries 361 * @entry: an entry within head, could be the head itself 362 * and if so we won't cut the list 363 * 364 * This helper moves the initial part of @head, up to and 365 * including @entry, from @head to @list. You should 366 * pass on @entry an element you know is on @head. @list 367 * should be an empty list or a list you do not care about 368 * losing its data. 369 * 370 */ 371 static inline void list_cut_position(struct list_head *list, 372 struct list_head *head, struct list_head *entry) 373 { 374 if (list_empty(head)) 375 return; 376 if (list_is_singular(head) && 377 (head->next != entry && head != entry)) 378 return; 379 if (entry == head) 380 INIT_LIST_HEAD(list); 381 else 382 __list_cut_position(list, head, entry); 383 } 384 385 /** 386 * list_cut_before - cut a list into two, before given entry 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 * 391 * This helper moves the initial part of @head, up to but 392 * excluding @entry, from @head to @list. You should pass 393 * in @entry an element you know is on @head. @list should 394 * be an empty list or a list you do not care about losing 395 * its data. 396 * If @entry == @head, all entries on @head are moved to 397 * @list. 398 */ 399 static inline void list_cut_before(struct list_head *list, 400 struct list_head *head, 401 struct list_head *entry) 402 { 403 if (head->next == entry) { 404 INIT_LIST_HEAD(list); 405 return; 406 } 407 list->next = head->next; 408 list->next->prev = list; 409 list->prev = entry->prev; 410 list->prev->next = list; 411 head->next = entry; 412 entry->prev = head; 413 } 414 415 static inline void __list_splice(const struct list_head *list, 416 struct list_head *prev, 417 struct list_head *next) 418 { 419 struct list_head *first = list->next; 420 struct list_head *last = list->prev; 421 422 first->prev = prev; 423 prev->next = first; 424 425 last->next = next; 426 next->prev = last; 427 } 428 429 /** 430 * list_splice - join two lists, this is designed for stacks 431 * @list: the new list to add. 432 * @head: the place to add it in the first list. 433 */ 434 static inline void list_splice(const struct list_head *list, 435 struct list_head *head) 436 { 437 if (!list_empty(list)) 438 __list_splice(list, head, head->next); 439 } 440 441 /** 442 * list_splice_tail - join two lists, each list being a queue 443 * @list: the new list to add. 444 * @head: the place to add it in the first list. 445 */ 446 static inline void list_splice_tail(struct list_head *list, 447 struct list_head *head) 448 { 449 if (!list_empty(list)) 450 __list_splice(list, head->prev, head); 451 } 452 453 /** 454 * list_splice_init - join two lists and reinitialise the emptied list. 455 * @list: the new list to add. 456 * @head: the place to add it in the first list. 457 * 458 * The list at @list is reinitialised 459 */ 460 static inline void list_splice_init(struct list_head *list, 461 struct list_head *head) 462 { 463 if (!list_empty(list)) { 464 __list_splice(list, head, head->next); 465 INIT_LIST_HEAD(list); 466 } 467 } 468 469 /** 470 * list_splice_tail_init - join two lists and reinitialise the emptied list 471 * @list: the new list to add. 472 * @head: the place to add it in the first list. 473 * 474 * Each of the lists is a queue. 475 * The list at @list is reinitialised 476 */ 477 static inline void list_splice_tail_init(struct list_head *list, 478 struct list_head *head) 479 { 480 if (!list_empty(list)) { 481 __list_splice(list, head->prev, head); 482 INIT_LIST_HEAD(list); 483 } 484 } 485 486 /** 487 * list_entry - get the struct for this entry 488 * @ptr: the &struct list_head pointer. 489 * @type: the type of the struct this is embedded in. 490 * @member: the name of the list_head within the struct. 491 */ 492 #define list_entry(ptr, type, member) \ 493 container_of(ptr, type, member) 494 495 /** 496 * list_first_entry - get the first element from a list 497 * @ptr: the list head to take the element from. 498 * @type: the type of the struct this is embedded in. 499 * @member: the name of the list_head within the struct. 500 * 501 * Note, that list is expected to be not empty. 502 */ 503 #define list_first_entry(ptr, type, member) \ 504 list_entry((ptr)->next, type, member) 505 506 /** 507 * list_last_entry - get the last element from a list 508 * @ptr: the list head to take the element from. 509 * @type: the type of the struct this is embedded in. 510 * @member: the name of the list_head within the struct. 511 * 512 * Note, that list is expected to be not empty. 513 */ 514 #define list_last_entry(ptr, type, member) \ 515 list_entry((ptr)->prev, type, member) 516 517 /** 518 * list_first_entry_or_null - get the first element from a list 519 * @ptr: the list head to take the element from. 520 * @type: the type of the struct this is embedded in. 521 * @member: the name of the list_head within the struct. 522 * 523 * Note that if the list is empty, it returns NULL. 524 */ 525 #define list_first_entry_or_null(ptr, type, member) ({ \ 526 struct list_head *head__ = (ptr); \ 527 struct list_head *pos__ = READ_ONCE(head__->next); \ 528 pos__ != head__ ? list_entry(pos__, type, member) : NULL; \ 529 }) 530 531 /** 532 * list_next_entry - get the next element in list 533 * @pos: the type * to cursor 534 * @member: the name of the list_head within the struct. 535 */ 536 #define list_next_entry(pos, member) \ 537 list_entry((pos)->member.next, typeof(*(pos)), member) 538 539 /** 540 * list_prev_entry - get the prev element in list 541 * @pos: the type * to cursor 542 * @member: the name of the list_head within the struct. 543 */ 544 #define list_prev_entry(pos, member) \ 545 list_entry((pos)->member.prev, typeof(*(pos)), member) 546 547 /** 548 * list_for_each - iterate over a list 549 * @pos: the &struct list_head to use as a loop cursor. 550 * @head: the head for your list. 551 */ 552 #define list_for_each(pos, head) \ 553 for (pos = (head)->next; pos != (head); pos = pos->next) 554 555 /** 556 * list_for_each_continue - continue iteration over a list 557 * @pos: the &struct list_head to use as a loop cursor. 558 * @head: the head for your list. 559 * 560 * Continue to iterate over a list, continuing after the current position. 561 */ 562 #define list_for_each_continue(pos, head) \ 563 for (pos = pos->next; pos != (head); pos = pos->next) 564 565 /** 566 * list_for_each_prev - iterate over a list backwards 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_prev(pos, head) \ 571 for (pos = (head)->prev; pos != (head); pos = pos->prev) 572 573 /** 574 * list_for_each_safe - iterate over a list safe against removal of list entry 575 * @pos: the &struct list_head to use as a loop cursor. 576 * @n: another &struct list_head to use as temporary storage 577 * @head: the head for your list. 578 */ 579 #define list_for_each_safe(pos, n, head) \ 580 for (pos = (head)->next, n = pos->next; pos != (head); \ 581 pos = n, n = pos->next) 582 583 /** 584 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry 585 * @pos: the &struct list_head to use as a loop cursor. 586 * @n: another &struct list_head to use as temporary storage 587 * @head: the head for your list. 588 */ 589 #define list_for_each_prev_safe(pos, n, head) \ 590 for (pos = (head)->prev, n = pos->prev; \ 591 pos != (head); \ 592 pos = n, n = pos->prev) 593 594 /** 595 * list_for_each_entry - iterate over list of given type 596 * @pos: the type * to use as a loop cursor. 597 * @head: the head for your list. 598 * @member: the name of the list_head within the struct. 599 */ 600 #define list_for_each_entry(pos, head, member) \ 601 for (pos = list_first_entry(head, typeof(*pos), member); \ 602 &pos->member != (head); \ 603 pos = list_next_entry(pos, member)) 604 605 /** 606 * list_for_each_entry_reverse - iterate backwards over list of given type. 607 * @pos: the type * to use as a loop cursor. 608 * @head: the head for your list. 609 * @member: the name of the list_head within the struct. 610 */ 611 #define list_for_each_entry_reverse(pos, head, member) \ 612 for (pos = list_last_entry(head, typeof(*pos), member); \ 613 &pos->member != (head); \ 614 pos = list_prev_entry(pos, member)) 615 616 /** 617 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue() 618 * @pos: the type * to use as a start point 619 * @head: the head of the list 620 * @member: the name of the list_head within the struct. 621 * 622 * Prepares a pos entry for use as a start point in list_for_each_entry_continue(). 623 */ 624 #define list_prepare_entry(pos, head, member) \ 625 ((pos) ? : list_entry(head, typeof(*pos), member)) 626 627 /** 628 * list_for_each_entry_continue - continue iteration over list of given type 629 * @pos: the type * to use as a loop cursor. 630 * @head: the head for your list. 631 * @member: the name of the list_head within the struct. 632 * 633 * Continue to iterate over list of given type, continuing after 634 * the current position. 635 */ 636 #define list_for_each_entry_continue(pos, head, member) \ 637 for (pos = list_next_entry(pos, member); \ 638 &pos->member != (head); \ 639 pos = list_next_entry(pos, member)) 640 641 /** 642 * list_for_each_entry_continue_reverse - iterate backwards from the given point 643 * @pos: the type * to use as a loop cursor. 644 * @head: the head for your list. 645 * @member: the name of the list_head within the struct. 646 * 647 * Start to iterate over list of given type backwards, continuing after 648 * the current position. 649 */ 650 #define list_for_each_entry_continue_reverse(pos, head, member) \ 651 for (pos = list_prev_entry(pos, member); \ 652 &pos->member != (head); \ 653 pos = list_prev_entry(pos, member)) 654 655 /** 656 * list_for_each_entry_from - iterate over list of given type from the current point 657 * @pos: the type * to use as a loop cursor. 658 * @head: the head for your list. 659 * @member: the name of the list_head within the struct. 660 * 661 * Iterate over list of given type, continuing from current position. 662 */ 663 #define list_for_each_entry_from(pos, head, member) \ 664 for (; &pos->member != (head); \ 665 pos = list_next_entry(pos, member)) 666 667 /** 668 * list_for_each_entry_from_reverse - iterate backwards over list of given type 669 * from the current point 670 * @pos: the type * to use as a loop cursor. 671 * @head: the head for your list. 672 * @member: the name of the list_head within the struct. 673 * 674 * Iterate backwards over list of given type, continuing from current position. 675 */ 676 #define list_for_each_entry_from_reverse(pos, head, member) \ 677 for (; &pos->member != (head); \ 678 pos = list_prev_entry(pos, member)) 679 680 /** 681 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry 682 * @pos: the type * to use as a loop cursor. 683 * @n: another type * to use as temporary storage 684 * @head: the head for your list. 685 * @member: the name of the list_head within the struct. 686 */ 687 #define list_for_each_entry_safe(pos, n, head, member) \ 688 for (pos = list_first_entry(head, typeof(*pos), member), \ 689 n = list_next_entry(pos, member); \ 690 &pos->member != (head); \ 691 pos = n, n = list_next_entry(n, member)) 692 693 /** 694 * list_for_each_entry_safe_continue - continue list iteration safe against removal 695 * @pos: the type * to use as a loop cursor. 696 * @n: another type * to use as temporary storage 697 * @head: the head for your list. 698 * @member: the name of the list_head within the struct. 699 * 700 * Iterate over list of given type, continuing after current point, 701 * safe against removal of list entry. 702 */ 703 #define list_for_each_entry_safe_continue(pos, n, head, member) \ 704 for (pos = list_next_entry(pos, member), \ 705 n = list_next_entry(pos, member); \ 706 &pos->member != (head); \ 707 pos = n, n = list_next_entry(n, member)) 708 709 /** 710 * list_for_each_entry_safe_from - iterate over list from current point safe against removal 711 * @pos: the type * to use as a loop cursor. 712 * @n: another type * to use as temporary storage 713 * @head: the head for your list. 714 * @member: the name of the list_head within the struct. 715 * 716 * Iterate over list of given type from current point, safe against 717 * removal of list entry. 718 */ 719 #define list_for_each_entry_safe_from(pos, n, head, member) \ 720 for (n = list_next_entry(pos, member); \ 721 &pos->member != (head); \ 722 pos = n, n = list_next_entry(n, member)) 723 724 /** 725 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal 726 * @pos: the type * to use as a loop cursor. 727 * @n: another type * to use as temporary storage 728 * @head: the head for your list. 729 * @member: the name of the list_head within the struct. 730 * 731 * Iterate backwards over list of given type, safe against removal 732 * of list entry. 733 */ 734 #define list_for_each_entry_safe_reverse(pos, n, head, member) \ 735 for (pos = list_last_entry(head, typeof(*pos), member), \ 736 n = list_prev_entry(pos, member); \ 737 &pos->member != (head); \ 738 pos = n, n = list_prev_entry(n, member)) 739 740 /** 741 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop 742 * @pos: the loop cursor used in the list_for_each_entry_safe loop 743 * @n: temporary storage used in list_for_each_entry_safe 744 * @member: the name of the list_head within the struct. 745 * 746 * list_safe_reset_next is not safe to use in general if the list may be 747 * modified concurrently (eg. the lock is dropped in the loop body). An 748 * exception to this is if the cursor element (pos) is pinned in the list, 749 * and list_safe_reset_next is called after re-taking the lock and before 750 * completing the current iteration of the loop body. 751 */ 752 #define list_safe_reset_next(pos, n, member) \ 753 n = list_next_entry(pos, member) 754 755 /* 756 * Double linked lists with a single pointer list head. 757 * Mostly useful for hash tables where the two pointer list head is 758 * too wasteful. 759 * You lose the ability to access the tail in O(1). 760 */ 761 762 #define HLIST_HEAD_INIT { .first = NULL } 763 #define HLIST_HEAD(name) struct hlist_head name = { .first = NULL } 764 #define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL) 765 static inline void INIT_HLIST_NODE(struct hlist_node *h) 766 { 767 h->next = NULL; 768 h->pprev = NULL; 769 } 770 771 /** 772 * hlist_unhashed - Has node been removed from list and reinitialized? 773 * @h: Node to be checked 774 * 775 * Not that not all removal functions will leave a node in unhashed 776 * state. For example, hlist_nulls_del_init_rcu() does leave the 777 * node in unhashed state, but hlist_nulls_del() does not. 778 */ 779 static inline int hlist_unhashed(const struct hlist_node *h) 780 { 781 return !h->pprev; 782 } 783 784 /** 785 * hlist_unhashed_lockless - Version of hlist_unhashed for lockless use 786 * @h: Node to be checked 787 * 788 * This variant of hlist_unhashed() must be used in lockless contexts 789 * to avoid potential load-tearing. The READ_ONCE() is paired with the 790 * various WRITE_ONCE() in hlist helpers that are defined below. 791 */ 792 static inline int hlist_unhashed_lockless(const struct hlist_node *h) 793 { 794 return !READ_ONCE(h->pprev); 795 } 796 797 /** 798 * hlist_empty - Is the specified hlist_head structure an empty hlist? 799 * @h: Structure to check. 800 */ 801 static inline int hlist_empty(const struct hlist_head *h) 802 { 803 return !READ_ONCE(h->first); 804 } 805 806 static inline void __hlist_del(struct hlist_node *n) 807 { 808 struct hlist_node *next = n->next; 809 struct hlist_node **pprev = n->pprev; 810 811 WRITE_ONCE(*pprev, next); 812 if (next) 813 WRITE_ONCE(next->pprev, pprev); 814 } 815 816 /** 817 * hlist_del - Delete the specified hlist_node from its list 818 * @n: Node to delete. 819 * 820 * Note that this function leaves the node in hashed state. Use 821 * hlist_del_init() or similar instead to unhash @n. 822 */ 823 static inline void hlist_del(struct hlist_node *n) 824 { 825 __hlist_del(n); 826 n->next = LIST_POISON1; 827 n->pprev = LIST_POISON2; 828 } 829 830 /** 831 * hlist_del_init - Delete the specified hlist_node from its list and initialize 832 * @n: Node to delete. 833 * 834 * Note that this function leaves the node in unhashed state. 835 */ 836 static inline void hlist_del_init(struct hlist_node *n) 837 { 838 if (!hlist_unhashed(n)) { 839 __hlist_del(n); 840 INIT_HLIST_NODE(n); 841 } 842 } 843 844 /** 845 * hlist_add_head - add a new entry at the beginning of the hlist 846 * @n: new entry to be added 847 * @h: hlist head to add it after 848 * 849 * Insert a new entry after the specified head. 850 * This is good for implementing stacks. 851 */ 852 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h) 853 { 854 struct hlist_node *first = h->first; 855 WRITE_ONCE(n->next, first); 856 if (first) 857 WRITE_ONCE(first->pprev, &n->next); 858 WRITE_ONCE(h->first, n); 859 WRITE_ONCE(n->pprev, &h->first); 860 } 861 862 /** 863 * hlist_add_before - add a new entry before the one specified 864 * @n: new entry to be added 865 * @next: hlist node to add it before, which must be non-NULL 866 */ 867 static inline void hlist_add_before(struct hlist_node *n, 868 struct hlist_node *next) 869 { 870 WRITE_ONCE(n->pprev, next->pprev); 871 WRITE_ONCE(n->next, next); 872 WRITE_ONCE(next->pprev, &n->next); 873 WRITE_ONCE(*(n->pprev), n); 874 } 875 876 /** 877 * hlist_add_behing - add a new entry after the one specified 878 * @n: new entry to be added 879 * @prev: hlist node to add it after, which must be non-NULL 880 */ 881 static inline void hlist_add_behind(struct hlist_node *n, 882 struct hlist_node *prev) 883 { 884 WRITE_ONCE(n->next, prev->next); 885 WRITE_ONCE(prev->next, n); 886 WRITE_ONCE(n->pprev, &prev->next); 887 888 if (n->next) 889 WRITE_ONCE(n->next->pprev, &n->next); 890 } 891 892 /** 893 * hlist_add_fake - create a fake hlist consisting of a single headless node 894 * @n: Node to make a fake list out of 895 * 896 * This makes @n appear to be its own predecessor on a headless hlist. 897 * The point of this is to allow things like hlist_del() to work correctly 898 * in cases where there is no list. 899 */ 900 static inline void hlist_add_fake(struct hlist_node *n) 901 { 902 n->pprev = &n->next; 903 } 904 905 /** 906 * hlist_fake: Is this node a fake hlist? 907 * @h: Node to check for being a self-referential fake hlist. 908 */ 909 static inline bool hlist_fake(struct hlist_node *h) 910 { 911 return h->pprev == &h->next; 912 } 913 914 /** 915 * hlist_is_singular_node - is node the only element of the specified hlist? 916 * @n: Node to check for singularity. 917 * @h: Header for potentially singular list. 918 * 919 * Check whether the node is the only node of the head without 920 * accessing head, thus avoiding unnecessary cache misses. 921 */ 922 static inline bool 923 hlist_is_singular_node(struct hlist_node *n, struct hlist_head *h) 924 { 925 return !n->next && n->pprev == &h->first; 926 } 927 928 /** 929 * hlist_move_list - Move an hlist 930 * @old: hlist_head for old list. 931 * @new: hlist_head for new list. 932 * 933 * Move a list from one list head to another. Fixup the pprev 934 * reference of the first entry if it exists. 935 */ 936 static inline void hlist_move_list(struct hlist_head *old, 937 struct hlist_head *new) 938 { 939 new->first = old->first; 940 if (new->first) 941 new->first->pprev = &new->first; 942 old->first = NULL; 943 } 944 945 #define hlist_entry(ptr, type, member) container_of(ptr,type,member) 946 947 #define hlist_for_each(pos, head) \ 948 for (pos = (head)->first; pos ; pos = pos->next) 949 950 #define hlist_for_each_safe(pos, n, head) \ 951 for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \ 952 pos = n) 953 954 #define hlist_entry_safe(ptr, type, member) \ 955 ({ typeof(ptr) ____ptr = (ptr); \ 956 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \ 957 }) 958 959 /** 960 * hlist_for_each_entry - iterate over list of given type 961 * @pos: the type * to use as a loop cursor. 962 * @head: the head for your list. 963 * @member: the name of the hlist_node within the struct. 964 */ 965 #define hlist_for_each_entry(pos, head, member) \ 966 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\ 967 pos; \ 968 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member)) 969 970 /** 971 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point 972 * @pos: the type * to use as a loop cursor. 973 * @member: the name of the hlist_node within the struct. 974 */ 975 #define hlist_for_each_entry_continue(pos, member) \ 976 for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\ 977 pos; \ 978 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member)) 979 980 /** 981 * hlist_for_each_entry_from - iterate over a hlist continuing from current point 982 * @pos: the type * to use as a loop cursor. 983 * @member: the name of the hlist_node within the struct. 984 */ 985 #define hlist_for_each_entry_from(pos, member) \ 986 for (; pos; \ 987 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member)) 988 989 /** 990 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry 991 * @pos: the type * to use as a loop cursor. 992 * @n: another &struct hlist_node to use as temporary storage 993 * @head: the head for your list. 994 * @member: the name of the hlist_node within the struct. 995 */ 996 #define hlist_for_each_entry_safe(pos, n, head, member) \ 997 for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\ 998 pos && ({ n = pos->member.next; 1; }); \ 999 pos = hlist_entry_safe(n, typeof(*pos), member)) 1000 1001 #endif 1002