plist.h 7.1 KB

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  1. /*
  2. * Descending-priority-sorted double-linked list
  3. *
  4. * (C) 2002-2003 Intel Corp
  5. * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
  6. *
  7. * 2001-2005 (c) MontaVista Software, Inc.
  8. * Daniel Walker <dwalker@mvista.com>
  9. *
  10. * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
  11. *
  12. * Simplifications of the original code by
  13. * Oleg Nesterov <oleg@tv-sign.ru>
  14. *
  15. * Licensed under the FSF's GNU Public License v2 or later.
  16. *
  17. * Based on simple lists (include/linux/list.h).
  18. *
  19. * This is a priority-sorted list of nodes; each node has a
  20. * priority from INT_MIN (highest) to INT_MAX (lowest).
  21. *
  22. * Addition is O(K), removal is O(1), change of priority of a node is
  23. * O(K) and K is the number of RT priority levels used in the system.
  24. * (1 <= K <= 99)
  25. *
  26. * This list is really a list of lists:
  27. *
  28. * - The tier 1 list is the prio_list, different priority nodes.
  29. *
  30. * - The tier 2 list is the node_list, serialized nodes.
  31. *
  32. * Simple ASCII art explanation:
  33. *
  34. * |HEAD |
  35. * | |
  36. * |prio_list.prev|<------------------------------------|
  37. * |prio_list.next|<->|pl|<->|pl|<--------------->|pl|<-|
  38. * |10 | |10| |21| |21| |21| |40| (prio)
  39. * | | | | | | | | | | | |
  40. * | | | | | | | | | | | |
  41. * |node_list.next|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
  42. * |node_list.prev|<------------------------------------|
  43. *
  44. * The nodes on the prio_list list are sorted by priority to simplify
  45. * the insertion of new nodes. There are no nodes with duplicate
  46. * priorites on the list.
  47. *
  48. * The nodes on the node_list is ordered by priority and can contain
  49. * entries which have the same priority. Those entries are ordered
  50. * FIFO
  51. *
  52. * Addition means: look for the prio_list node in the prio_list
  53. * for the priority of the node and insert it before the node_list
  54. * entry of the next prio_list node. If it is the first node of
  55. * that priority, add it to the prio_list in the right position and
  56. * insert it into the serialized node_list list
  57. *
  58. * Removal means remove it from the node_list and remove it from
  59. * the prio_list if the node_list list_head is non empty. In case
  60. * of removal from the prio_list it must be checked whether other
  61. * entries of the same priority are on the list or not. If there
  62. * is another entry of the same priority then this entry has to
  63. * replace the removed entry on the prio_list. If the entry which
  64. * is removed is the only entry of this priority then a simple
  65. * remove from both list is sufficient.
  66. *
  67. * INT_MIN is the highest priority, 0 is the medium highest, INT_MAX
  68. * is lowest priority.
  69. *
  70. * No locking is done, up to the caller.
  71. *
  72. */
  73. #ifndef _LINUX_PLIST_H_
  74. #define _LINUX_PLIST_H_
  75. #include <linux/kernel.h>
  76. #include <linux/list.h>
  77. #include <linux/spinlock_types.h>
  78. struct plist_head {
  79. struct list_head prio_list;
  80. struct list_head node_list;
  81. #ifdef CONFIG_DEBUG_PI_LIST
  82. spinlock_t *lock;
  83. #endif
  84. };
  85. struct plist_node {
  86. int prio;
  87. struct plist_head plist;
  88. };
  89. #ifdef CONFIG_DEBUG_PI_LIST
  90. # define PLIST_HEAD_LOCK_INIT(_lock) .lock = _lock
  91. #else
  92. # define PLIST_HEAD_LOCK_INIT(_lock)
  93. #endif
  94. /**
  95. * PLIST_HEAD_INIT - static struct plist_head initializer
  96. * @head: struct plist_head variable name
  97. * @_lock: lock to initialize for this list
  98. */
  99. #define PLIST_HEAD_INIT(head, _lock) \
  100. { \
  101. .prio_list = LIST_HEAD_INIT((head).prio_list), \
  102. .node_list = LIST_HEAD_INIT((head).node_list), \
  103. PLIST_HEAD_LOCK_INIT(&(_lock)) \
  104. }
  105. /**
  106. * PLIST_NODE_INIT - static struct plist_node initializer
  107. * @node: struct plist_node variable name
  108. * @__prio: initial node priority
  109. */
  110. #define PLIST_NODE_INIT(node, __prio) \
  111. { \
  112. .prio = (__prio), \
  113. .plist = PLIST_HEAD_INIT((node).plist, NULL), \
  114. }
  115. /**
  116. * plist_head_init - dynamic struct plist_head initializer
  117. * @head: &struct plist_head pointer
  118. * @lock: list spinlock, remembered for debugging
  119. */
  120. static inline void
  121. plist_head_init(struct plist_head *head, spinlock_t *lock)
  122. {
  123. INIT_LIST_HEAD(&head->prio_list);
  124. INIT_LIST_HEAD(&head->node_list);
  125. #ifdef CONFIG_DEBUG_PI_LIST
  126. head->lock = lock;
  127. #endif
  128. }
  129. /**
  130. * plist_node_init - Dynamic struct plist_node initializer
  131. * @node: &struct plist_node pointer
  132. * @prio: initial node priority
  133. */
  134. static inline void plist_node_init(struct plist_node *node, int prio)
  135. {
  136. node->prio = prio;
  137. plist_head_init(&node->plist, NULL);
  138. }
  139. extern void plist_add(struct plist_node *node, struct plist_head *head);
  140. extern void plist_del(struct plist_node *node, struct plist_head *head);
  141. /**
  142. * plist_for_each - iterate over the plist
  143. * @pos: the type * to use as a loop counter
  144. * @head: the head for your list
  145. */
  146. #define plist_for_each(pos, head) \
  147. list_for_each_entry(pos, &(head)->node_list, plist.node_list)
  148. /**
  149. * plist_for_each_safe - iterate safely over a plist of given type
  150. * @pos: the type * to use as a loop counter
  151. * @n: another type * to use as temporary storage
  152. * @head: the head for your list
  153. *
  154. * Iterate over a plist of given type, safe against removal of list entry.
  155. */
  156. #define plist_for_each_safe(pos, n, head) \
  157. list_for_each_entry_safe(pos, n, &(head)->node_list, plist.node_list)
  158. /**
  159. * plist_for_each_entry - iterate over list of given type
  160. * @pos: the type * to use as a loop counter
  161. * @head: the head for your list
  162. * @mem: the name of the list_struct within the struct
  163. */
  164. #define plist_for_each_entry(pos, head, mem) \
  165. list_for_each_entry(pos, &(head)->node_list, mem.plist.node_list)
  166. /**
  167. * plist_for_each_entry_safe - iterate safely over list of given type
  168. * @pos: the type * to use as a loop counter
  169. * @n: another type * to use as temporary storage
  170. * @head: the head for your list
  171. * @m: the name of the list_struct within the struct
  172. *
  173. * Iterate over list of given type, safe against removal of list entry.
  174. */
  175. #define plist_for_each_entry_safe(pos, n, head, m) \
  176. list_for_each_entry_safe(pos, n, &(head)->node_list, m.plist.node_list)
  177. /**
  178. * plist_head_empty - return !0 if a plist_head is empty
  179. * @head: &struct plist_head pointer
  180. */
  181. static inline int plist_head_empty(const struct plist_head *head)
  182. {
  183. return list_empty(&head->node_list);
  184. }
  185. /**
  186. * plist_node_empty - return !0 if plist_node is not on a list
  187. * @node: &struct plist_node pointer
  188. */
  189. static inline int plist_node_empty(const struct plist_node *node)
  190. {
  191. return plist_head_empty(&node->plist);
  192. }
  193. /* All functions below assume the plist_head is not empty. */
  194. /**
  195. * plist_first_entry - get the struct for the first entry
  196. * @head: the &struct plist_head pointer
  197. * @type: the type of the struct this is embedded in
  198. * @member: the name of the list_struct within the struct
  199. */
  200. #ifdef CONFIG_DEBUG_PI_LIST
  201. # define plist_first_entry(head, type, member) \
  202. ({ \
  203. WARN_ON(plist_head_empty(head)); \
  204. container_of(plist_first(head), type, member); \
  205. })
  206. #else
  207. # define plist_first_entry(head, type, member) \
  208. container_of(plist_first(head), type, member)
  209. #endif
  210. /**
  211. * plist_first - return the first node (and thus, highest priority)
  212. * @head: the &struct plist_head pointer
  213. *
  214. * Assumes the plist is _not_ empty.
  215. */
  216. static inline struct plist_node* plist_first(const struct plist_head *head)
  217. {
  218. return list_entry(head->node_list.next,
  219. struct plist_node, plist.node_list);
  220. }
  221. #endif