llist.h 6.2 KB

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  1. #ifndef LLIST_H
  2. #define LLIST_H
  3. /*
  4. * Lock-less NULL terminated single linked list
  5. *
  6. * If there are multiple producers and multiple consumers, llist_add
  7. * can be used in producers and llist_del_all can be used in
  8. * consumers. They can work simultaneously without lock. But
  9. * llist_del_first can not be used here. Because llist_del_first
  10. * depends on list->first->next does not changed if list->first is not
  11. * changed during its operation, but llist_del_first, llist_add,
  12. * llist_add (or llist_del_all, llist_add, llist_add) sequence in
  13. * another consumer may violate that.
  14. *
  15. * If there are multiple producers and one consumer, llist_add can be
  16. * used in producers and llist_del_all or llist_del_first can be used
  17. * in the consumer.
  18. *
  19. * This can be summarized as follow:
  20. *
  21. * | add | del_first | del_all
  22. * add | - | - | -
  23. * del_first | | L | L
  24. * del_all | | | -
  25. *
  26. * Where "-" stands for no lock is needed, while "L" stands for lock
  27. * is needed.
  28. *
  29. * The list entries deleted via llist_del_all can be traversed with
  30. * traversing function such as llist_for_each etc. But the list
  31. * entries can not be traversed safely before deleted from the list.
  32. * The order of deleted entries is from the newest to the oldest added
  33. * one. If you want to traverse from the oldest to the newest, you
  34. * must reverse the order by yourself before traversing.
  35. *
  36. * The basic atomic operation of this list is cmpxchg on long. On
  37. * architectures that don't have NMI-safe cmpxchg implementation, the
  38. * list can NOT be used in NMI handlers. So code that uses the list in
  39. * an NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
  40. *
  41. * Copyright 2010,2011 Intel Corp.
  42. * Author: Huang Ying <ying.huang@intel.com>
  43. *
  44. * This program is free software; you can redistribute it and/or
  45. * modify it under the terms of the GNU General Public License version
  46. * 2 as published by the Free Software Foundation;
  47. *
  48. * This program is distributed in the hope that it will be useful,
  49. * but WITHOUT ANY WARRANTY; without even the implied warranty of
  50. * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  51. * GNU General Public License for more details.
  52. *
  53. * You should have received a copy of the GNU General Public License
  54. * along with this program; if not, write to the Free Software
  55. * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  56. */
  57. #include <linux/kernel.h>
  58. #include <asm/system.h>
  59. #include <asm/processor.h>
  60. struct llist_head {
  61. struct llist_node *first;
  62. };
  63. struct llist_node {
  64. struct llist_node *next;
  65. };
  66. #define LLIST_HEAD_INIT(name) { NULL }
  67. #define LLIST_HEAD(name) struct llist_head name = LLIST_HEAD_INIT(name)
  68. /**
  69. * init_llist_head - initialize lock-less list head
  70. * @head: the head for your lock-less list
  71. */
  72. static inline void init_llist_head(struct llist_head *list)
  73. {
  74. list->first = NULL;
  75. }
  76. /**
  77. * llist_entry - get the struct of this entry
  78. * @ptr: the &struct llist_node pointer.
  79. * @type: the type of the struct this is embedded in.
  80. * @member: the name of the llist_node within the struct.
  81. */
  82. #define llist_entry(ptr, type, member) \
  83. container_of(ptr, type, member)
  84. /**
  85. * llist_for_each - iterate over some deleted entries of a lock-less list
  86. * @pos: the &struct llist_node to use as a loop cursor
  87. * @node: the first entry of deleted list entries
  88. *
  89. * In general, some entries of the lock-less list can be traversed
  90. * safely only after being deleted from list, so start with an entry
  91. * instead of list head.
  92. *
  93. * If being used on entries deleted from lock-less list directly, the
  94. * traverse order is from the newest to the oldest added entry. If
  95. * you want to traverse from the oldest to the newest, you must
  96. * reverse the order by yourself before traversing.
  97. */
  98. #define llist_for_each(pos, node) \
  99. for ((pos) = (node); pos; (pos) = (pos)->next)
  100. /**
  101. * llist_for_each_entry - iterate over some deleted entries of lock-less list of given type
  102. * @pos: the type * to use as a loop cursor.
  103. * @node: the fist entry of deleted list entries.
  104. * @member: the name of the llist_node with the struct.
  105. *
  106. * In general, some entries of the lock-less list can be traversed
  107. * safely only after being removed from list, so start with an entry
  108. * instead of list head.
  109. *
  110. * If being used on entries deleted from lock-less list directly, the
  111. * traverse order is from the newest to the oldest added entry. If
  112. * you want to traverse from the oldest to the newest, you must
  113. * reverse the order by yourself before traversing.
  114. */
  115. #define llist_for_each_entry(pos, node, member) \
  116. for ((pos) = llist_entry((node), typeof(*(pos)), member); \
  117. &(pos)->member != NULL; \
  118. (pos) = llist_entry((pos)->member.next, typeof(*(pos)), member))
  119. /**
  120. * llist_empty - tests whether a lock-less list is empty
  121. * @head: the list to test
  122. *
  123. * Not guaranteed to be accurate or up to date. Just a quick way to
  124. * test whether the list is empty without deleting something from the
  125. * list.
  126. */
  127. static inline bool llist_empty(const struct llist_head *head)
  128. {
  129. return ACCESS_ONCE(head->first) == NULL;
  130. }
  131. static inline struct llist_node *llist_next(struct llist_node *node)
  132. {
  133. return node->next;
  134. }
  135. /**
  136. * llist_add - add a new entry
  137. * @new: new entry to be added
  138. * @head: the head for your lock-less list
  139. *
  140. * Return whether list is empty before adding.
  141. */
  142. static inline bool llist_add(struct llist_node *new, struct llist_head *head)
  143. {
  144. struct llist_node *entry, *old_entry;
  145. entry = head->first;
  146. for (;;) {
  147. old_entry = entry;
  148. new->next = entry;
  149. entry = cmpxchg(&head->first, old_entry, new);
  150. if (entry == old_entry)
  151. break;
  152. }
  153. return old_entry == NULL;
  154. }
  155. /**
  156. * llist_del_all - delete all entries from lock-less list
  157. * @head: the head of lock-less list to delete all entries
  158. *
  159. * If list is empty, return NULL, otherwise, delete all entries and
  160. * return the pointer to the first entry. The order of entries
  161. * deleted is from the newest to the oldest added one.
  162. */
  163. static inline struct llist_node *llist_del_all(struct llist_head *head)
  164. {
  165. return xchg(&head->first, NULL);
  166. }
  167. extern bool llist_add_batch(struct llist_node *new_first,
  168. struct llist_node *new_last,
  169. struct llist_head *head);
  170. extern struct llist_node *llist_del_first(struct llist_head *head);
  171. #endif /* LLIST_H */