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 #define _PLIST_HEAD_INIT(head)                          \
 100         .prio_list = LIST_HEAD_INIT((head).prio_list),  \
 101         .node_list = LIST_HEAD_INIT((head).node_list)
 102
 103 /**
 104  * PLIST_HEAD_INIT - static struct plist_head initializer
 105  * @head:       struct plist_head variable name
 106  * @_lock:      lock to initialize for this list
 107  */
 108 #define PLIST_HEAD_INIT(head, _lock)                    \
 109 {                                                       \
 110         _PLIST_HEAD_INIT(head),                         \
 111         PLIST_HEAD_LOCK_INIT(&(_lock))                  \
 112 }
 113
 114 /**
 115  * PLIST_NODE_INIT - static struct plist_node initializer
 116  * @node:       struct plist_node variable name
 117  * @__prio:     initial node priority
 118  */
 119 #define PLIST_NODE_INIT(node, __prio)                   \
 120 {                                                       \
 121         .prio  = (__prio),                              \
 122         .plist = { _PLIST_HEAD_INIT((node).plist) },    \
 123 }
 124
 125 /**
 126  * plist_head_init - dynamic struct plist_head initializer
 127  * @head:       &struct plist_head pointer
 128  * @lock:       list spinlock, remembered for debugging
 129  */
 130 static inline void
 131 plist_head_init(struct plist_head *head, spinlock_t *lock)
 132 {
 133         INIT_LIST_HEAD(&head->prio_list);
 134         INIT_LIST_HEAD(&head->node_list);
 135 #ifdef CONFIG_DEBUG_PI_LIST
 136         head->lock = lock;
 137 #endif
 138 }
 139
 140 /**
 141  * plist_node_init - Dynamic struct plist_node initializer
 142  * @node:       &struct plist_node pointer
 143  * @prio:       initial node priority
 144  */
 145 static inline void plist_node_init(struct plist_node *node, int prio)
 146 {
 147         node->prio = prio;
 148         plist_head_init(&node->plist, NULL);
 149 }
 150
 151 extern void plist_add(struct plist_node *node, struct plist_head *head);
 152 extern void plist_del(struct plist_node *node, struct plist_head *head);
 153
 154 /**
 155  * plist_for_each - iterate over the plist
 156  * @pos:        the type * to use as a loop counter
 157  * @head:       the head for your list
 158  */
 159 #define plist_for_each(pos, head)       \
 160          list_for_each_entry(pos, &(head)->node_list, plist.node_list)
 161
 162 /**
 163  * plist_for_each_safe - iterate safely over a plist of given type
 164  * @pos:        the type * to use as a loop counter
 165  * @n:  another type * to use as temporary storage
 166  * @head:       the head for your list
 167  *
 168  * Iterate over a plist of given type, safe against removal of list entry.
 169  */
 170 #define plist_for_each_safe(pos, n, head)       \
 171          list_for_each_entry_safe(pos, n, &(head)->node_list, plist.node_list)
 172
 173 /**
 174  * plist_for_each_entry - iterate over list of given type
 175  * @pos:        the type * to use as a loop counter
 176  * @head:       the head for your list
 177  * @mem:        the name of the list_struct within the struct
 178  */
 179 #define plist_for_each_entry(pos, head, mem)    \
 180          list_for_each_entry(pos, &(head)->node_list, mem.plist.node_list)
 181
 182 /**
 183  * plist_for_each_entry_safe - iterate safely over list of given type
 184  * @pos:        the type * to use as a loop counter
 185  * @n:          another type * to use as temporary storage
 186  * @head:       the head for your list
 187  * @m:          the name of the list_struct within the struct
 188  *
 189  * Iterate over list of given type, safe against removal of list entry.
 190  */
 191 #define plist_for_each_entry_safe(pos, n, head, m)      \
 192         list_for_each_entry_safe(pos, n, &(head)->node_list, m.plist.node_list)
 193
 194 /**
 195  * plist_head_empty - return !0 if a plist_head is empty
 196  * @head:       &struct plist_head pointer
 197  */
 198 static inline int plist_head_empty(const struct plist_head *head)
 199 {
 200         return list_empty(&head->node_list);
 201 }
 202
 203 /**
 204  * plist_node_empty - return !0 if plist_node is not on a list
 205  * @node:       &struct plist_node pointer
 206  */
 207 static inline int plist_node_empty(const struct plist_node *node)
 208 {
 209         return plist_head_empty(&node->plist);
 210 }
 211
 212 /* All functions below assume the plist_head is not empty. */
 213
 214 /**
 215  * plist_first_entry - get the struct for the first 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_first_entry(head, type, member)  \
 222 ({ \
 223         WARN_ON(plist_head_empty(head)); \
 224         container_of(plist_first(head), type, member); \
 225 })
 226 #else
 227 # define plist_first_entry(head, type, member)  \
 228         container_of(plist_first(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, plist.node_list);
 241 }
 242
 243 #endif