linux/include/linux/plist.h
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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
  76#include <linux/kernel.h>
  77#include <linux/list.h>
  78#include <linux/spinlock_types.h>
  79
  80struct plist_head {
  81        struct list_head prio_list;
  82        struct list_head node_list;
  83#ifdef CONFIG_DEBUG_PI_LIST
  84        spinlock_t *lock;
  85#endif
  86};
  87
  88struct plist_node {
  89        int                     prio;
  90        struct plist_head       plist;
  91};
  92
  93#ifdef CONFIG_DEBUG_PI_LIST
  94# define PLIST_HEAD_LOCK_INIT(_lock)    .lock = _lock
  95#else
  96# define PLIST_HEAD_LOCK_INIT(_lock)
  97#endif
  98
  99/**
 100 * PLIST_HEAD_INIT - static struct plist_head initializer
 101 * @head:       struct plist_head variable name
 102 * @_lock:      lock to initialize for this list
 103 */
 104#define PLIST_HEAD_INIT(head, _lock)                    \
 105{                                                       \
 106        .prio_list = LIST_HEAD_INIT((head).prio_list),  \
 107        .node_list = LIST_HEAD_INIT((head).node_list),  \
 108        PLIST_HEAD_LOCK_INIT(&(_lock))                  \
 109}
 110
 111/**
 112 * PLIST_NODE_INIT - static struct plist_node initializer
 113 * @node:       struct plist_node variable name
 114 * @__prio:     initial node priority
 115 */
 116#define PLIST_NODE_INIT(node, __prio)                   \
 117{                                                       \
 118        .prio  = (__prio),                              \
 119        .plist = PLIST_HEAD_INIT((node).plist, NULL),   \
 120}
 121
 122/**
 123 * plist_head_init - dynamic struct plist_head initializer
 124 * @head:       &struct plist_head pointer
 125 * @lock:       list spinlock, remembered for debugging
 126 */
 127static inline void
 128plist_head_init(struct plist_head *head, spinlock_t *lock)
 129{
 130        INIT_LIST_HEAD(&head->prio_list);
 131        INIT_LIST_HEAD(&head->node_list);
 132#ifdef CONFIG_DEBUG_PI_LIST
 133        head->lock = lock;
 134#endif
 135}
 136
 137/**
 138 * plist_node_init - Dynamic struct plist_node initializer
 139 * @node:       &struct plist_node pointer
 140 * @prio:       initial node priority
 141 */
 142static inline void plist_node_init(struct plist_node *node, int prio)
 143{
 144        node->prio = prio;
 145        plist_head_init(&node->plist, NULL);
 146}
 147
 148extern void plist_add(struct plist_node *node, struct plist_head *head);
 149extern void plist_del(struct plist_node *node, struct plist_head *head);
 150
 151/**
 152 * plist_for_each - iterate over the plist
 153 * @pos:        the type * to use as a loop counter
 154 * @head:       the head for your list
 155 */
 156#define plist_for_each(pos, head)       \
 157         list_for_each_entry(pos, &(head)->node_list, plist.node_list)
 158
 159/**
 160 * plist_for_each_safe - iterate safely over a plist of given type
 161 * @pos:        the type * to use as a loop counter
 162 * @n:  another type * to use as temporary storage
 163 * @head:       the head for your list
 164 *
 165 * Iterate over a plist of given type, safe against removal of list entry.
 166 */
 167#define plist_for_each_safe(pos, n, head)       \
 168         list_for_each_entry_safe(pos, n, &(head)->node_list, plist.node_list)
 169
 170/**
 171 * plist_for_each_entry - iterate over list of given type
 172 * @pos:        the type * to use as a loop counter
 173 * @head:       the head for your list
 174 * @mem:        the name of the list_struct within the struct
 175 */
 176#define plist_for_each_entry(pos, head, mem)    \
 177         list_for_each_entry(pos, &(head)->node_list, mem.plist.node_list)
 178
 179/**
 180 * plist_for_each_entry_safe - iterate safely over list of given type
 181 * @pos:        the type * to use as a loop counter
 182 * @n:          another type * to use as temporary storage
 183 * @head:       the head for your list
 184 * @m:          the name of the list_struct within the struct
 185 *
 186 * Iterate over list of given type, safe against removal of list entry.
 187 */
 188#define plist_for_each_entry_safe(pos, n, head, m)      \
 189        list_for_each_entry_safe(pos, n, &(head)->node_list, m.plist.node_list)
 190
 191/**
 192 * plist_head_empty - return !0 if a plist_head is empty
 193 * @head:       &struct plist_head pointer
 194 */
 195static inline int plist_head_empty(const struct plist_head *head)
 196{
 197        return list_empty(&head->node_list);
 198}
 199
 200/**
 201 * plist_node_empty - return !0 if plist_node is not on a list
 202 * @node:       &struct plist_node pointer
 203 */
 204static inline int plist_node_empty(const struct plist_node *node)
 205{
 206        return plist_head_empty(&node->plist);
 207}
 208
 209/* All functions below assume the plist_head is not empty. */
 210
 211/**
 212 * plist_first_entry - get the struct for the first entry
 213 * @head:       the &struct plist_head pointer
 214 * @type:       the type of the struct this is embedded in
 215 * @member:     the name of the list_struct within the struct
 216 */
 217#ifdef CONFIG_DEBUG_PI_LIST
 218# define plist_first_entry(head, type, member)  \
 219({ \
 220        WARN_ON(plist_head_empty(head)); \
 221        container_of(plist_first(head), type, member); \
 222})
 223#else
 224# define plist_first_entry(head, type, member)  \
 225        container_of(plist_first(head), type, member)
 226#endif
 227
 228/**
 229 * plist_first - return the first node (and thus, highest priority)
 230 * @head:       the &struct plist_head pointer
 231 *
 232 * Assumes the plist is _not_ empty.
 233 */
 234static inline struct plist_node* plist_first(const struct plist_head *head)
 235{
 236        return list_entry(head->node_list.next,
 237                          struct plist_node, plist.node_list);
 238}
 239
 240#endif
 241
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