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  * pl:prio_list (only for plist_node)
  35  * nl:node_list
  36  *   HEAD|             NODE(S)
  37  *       |
  38  *       ||------------------------------------|
  39  *       ||->|pl|<->|pl|<--------------->|pl|<-|
  40  *       |   |10|   |21|   |21|   |21|   |40|   (prio)
  41  *       |   |  |   |  |   |  |   |  |   |  |
  42  *       |   |  |   |  |   |  |   |  |   |  |
  43  * |->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
  44  * |-------------------------------------------|
  45  *
  46  * The nodes on the prio_list list are sorted by priority to simplify
  47  * the insertion of new nodes. There are no nodes with duplicate
  48  * priorites on the list.
  49  *
  50  * The nodes on the node_list are ordered by priority and can contain
  51  * entries which have the same priority. Those entries are ordered
  52  * FIFO
  53  *
  54  * Addition means: look for the prio_list node in the prio_list
  55  * for the priority of the node and insert it before the node_list
  56  * entry of the next prio_list node. If it is the first node of
  57  * that priority, add it to the prio_list in the right position and
  58  * insert it into the serialized node_list list
  59  *
  60  * Removal means remove it from the node_list and remove it from
  61  * the prio_list if the node_list list_head is non empty. In case
  62  * of removal from the prio_list it must be checked whether other
  63  * entries of the same priority are on the list or not. If there
  64  * is another entry of the same priority then this entry has to
  65  * replace the removed entry on the prio_list. If the entry which
  66  * is removed is the only entry of this priority then a simple
  67  * remove from both list is sufficient.
  68  *
  69  * INT_MIN is the highest priority, 0 is the medium highest, INT_MAX
  70  * is lowest priority.
  71  *
  72  * No locking is done, up to the caller.
  73  *
  74  */
  75 #ifndef _LINUX_PLIST_H_
  76 #define _LINUX_PLIST_H_
  77
  78 #include <linux/kernel.h>
  79 #include <linux/list.h>
  80
  81 struct plist_head {
  82         struct list_head node_list;
  83 };
  84
  85 struct plist_node {
  86         int                     prio;
  87         struct list_head        prio_list;
  88         struct list_head        node_list;
  89 };
  90
  91 /**
  92  * PLIST_HEAD_INIT - static struct plist_head initializer
  93  * @head:       struct plist_head variable name
  94  */
  95 #define PLIST_HEAD_INIT(head)                           \
  96 {                                                       \
  97         .node_list = LIST_HEAD_INIT((head).node_list)   \
  98 }
  99
 100 /**
 101  * PLIST_NODE_INIT - static struct plist_node initializer
 102  * @node:       struct plist_node variable name
 103  * @__prio:     initial node priority
 104  */
 105 #define PLIST_NODE_INIT(node, __prio)                   \
 106 {                                                       \
 107         .prio  = (__prio),                              \
 108         .prio_list = LIST_HEAD_INIT((node).prio_list),  \
 109         .node_list = LIST_HEAD_INIT((node).node_list),  \
 110 }
 111
 112 /**
 113  * plist_head_init - dynamic struct plist_head initializer
 114  * @head:       &struct plist_head pointer
 115  */
 116 static inline void
 117 plist_head_init(struct plist_head *head)
 118 {
 119         INIT_LIST_HEAD(&head->node_list);
 120 }
 121
 122 /**
 123  * plist_node_init - Dynamic struct plist_node initializer
 124  * @node:       &struct plist_node pointer
 125  * @prio:       initial node priority
 126  */
 127 static inline void plist_node_init(struct plist_node *node, int prio)
 128 {
 129         node->prio = prio;
 130         INIT_LIST_HEAD(&node->prio_list);
 131         INIT_LIST_HEAD(&node->node_list);
 132 }
 133
 134 extern void plist_add(struct plist_node *node, struct plist_head *head);
 135 extern void plist_del(struct plist_node *node, struct plist_head *head);
 136
 137 /**
 138  * plist_for_each - iterate over the plist
 139  * @pos:        the type * to use as a loop counter
 140  * @head:       the head for your list
 141  */
 142 #define plist_for_each(pos, head)       \
 143          list_for_each_entry(pos, &(head)->node_list, node_list)
 144
 145 /**
 146  * plist_for_each_safe - iterate safely over a plist of given type
 147  * @pos:        the type * to use as a loop counter
 148  * @n:  another type * to use as temporary storage
 149  * @head:       the head for your list
 150  *
 151  * Iterate over a plist of given type, safe against removal of list entry.
 152  */
 153 #define plist_for_each_safe(pos, n, head)       \
 154          list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)
 155
 156 /**
 157  * plist_for_each_entry - iterate over list of given type
 158  * @pos:        the type * to use as a loop counter
 159  * @head:       the head for your list
 160  * @mem:        the name of the list_struct within the struct
 161  */
 162 #define plist_for_each_entry(pos, head, mem)    \
 163          list_for_each_entry(pos, &(head)->node_list, mem.node_list)
 164
 165 /**
 166  * plist_for_each_entry_safe - iterate safely over list of given type
 167  * @pos:        the type * to use as a loop counter
 168  * @n:          another type * to use as temporary storage
 169  * @head:       the head for your list
 170  * @m:          the name of the list_struct within the struct
 171  *
 172  * Iterate over list of given type, safe against removal of list entry.
 173  */
 174 #define plist_for_each_entry_safe(pos, n, head, m)      \
 175         list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)
 176
 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 /**
 187  * plist_node_empty - return !0 if plist_node is not on a list
 188  * @node:       &struct plist_node pointer
 189  */
 190 static inline int plist_node_empty(const struct plist_node *node)
 191 {
 192         return list_empty(&node->node_list);
 193 }
 194
 195 /* All functions below assume the plist_head is not empty. */
 196
 197 /**
 198  * plist_first_entry - get the struct for the first entry
 199  * @head:       the &struct plist_head pointer
 200  * @type:       the type of the struct this is embedded in
 201  * @member:     the name of the list_struct within the struct
 202  */
 203 #ifdef CONFIG_DEBUG_PI_LIST
 204 # define plist_first_entry(head, type, member)  \
 205 ({ \
 206         WARN_ON(plist_head_empty(head)); \
 207         container_of(plist_first(head), type, member); \
 208 })
 209 #else
 210 # define plist_first_entry(head, type, member)  \
 211         container_of(plist_first(head), type, member)
 212 #endif
 213
 214 /**
 215  * plist_last_entry - get the struct for the last entry
 216  * @head:       the &struct plist_head pointer
 217  * @type:       the type of the struct this is embedded in
 218  * @member:     the name of the list_struct within the struct
 219  */
 220 #ifdef CONFIG_DEBUG_PI_LIST
 221 # define plist_last_entry(head, type, member)   \
 222 ({ \
 223         WARN_ON(plist_head_empty(head)); \
 224         container_of(plist_last(head), type, member); \
 225 })
 226 #else
 227 # define plist_last_entry(head, type, member)   \
 228         container_of(plist_last(head), type, member)
 229 #endif
 230
 231 /**
 232  * plist_first - return the first node (and thus, highest priority)
 233  * @head:       the &struct plist_head pointer
 234  *
 235  * Assumes the plist is _not_ empty.
 236  */
 237 static inline struct plist_node *plist_first(const struct plist_head *head)
 238 {
 239         return list_entry(head->node_list.next,
 240                           struct plist_node, node_list);
 241 }
 242
 243 /**
 244  * plist_last - return the last node (and thus, lowest priority)
 245  * @head:       the &struct plist_head pointer
 246  *
 247  * Assumes the plist is _not_ empty.
 248  */
 249 static inline struct plist_node *plist_last(const struct plist_head *head)
 250 {
 251         return list_entry(head->node_list.prev,
 252                           struct plist_node, node_list);
 253 }
 254
 255 #endif