include/linux/plist.h

   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
  80 struct 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
  88 struct 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  */
 127 static inline void
 128 plist_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  */
 142 static 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
 148 extern void plist_add(struct plist_node *node, struct plist_head *head);
 149 extern 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  */
 195 static 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  */
 204 static 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  */
 234 static 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