include/linux/list.h

   1 #ifndef _LINUX_LIST_H
   2 #define _LINUX_LIST_H
   3
   4 #ifndef ARCH_HAS_PREFETCH
   5 #define ARCH_HAS_PREFETCH
   6 static inline void prefetch(const void *x) {;}
   7 #endif
   8
   9 /*
  10  * Simple doubly linked list implementation.
  11  *
  12  * Some of the internal functions ("__xxx") are useful when
  13  * manipulating whole lists rather than single entries, as
  14  * sometimes we already know the next/prev entries and we can
  15  * generate better code by using them directly rather than
  16  * using the generic single-entry routines.
  17  */
  18
  19 struct list_head {
  20         struct list_head *next, *prev;
  21 };
  22
  23 #define LIST_HEAD_INIT(name) { &(name), &(name) }
  24
  25 #define LIST_HEAD(name) \
  26         struct list_head name = LIST_HEAD_INIT(name)
  27
  28 #define INIT_LIST_HEAD(ptr) do { \
  29         (ptr)->next = (ptr); (ptr)->prev = (ptr); \
  30 } while (0)
  31
  32 /*
  33  * Insert a new entry between two known consecutive entries.
  34  *
  35  * This is only for internal list manipulation where we know
  36  * the prev/next entries already!
  37  */
  38 static inline void __list_add(struct list_head *new,
  39                               struct list_head *prev,
  40                               struct list_head *next)
  41 {
  42         next->prev = new;
  43         new->next = next;
  44         new->prev = prev;
  45         prev->next = new;
  46 }
  47
  48 /**
  49  * list_add - add a new entry
  50  * @new: new entry to be added
  51  * @head: list head to add it after
  52  *
  53  * Insert a new entry after the specified head.
  54  * This is good for implementing stacks.
  55  */
  56 static inline void list_add(struct list_head *new, struct list_head *head)
  57 {
  58         __list_add(new, head, head->next);
  59 }
  60
  61 /**
  62  * list_add_tail - add a new entry
  63  * @new: new entry to be added
  64  * @head: list head to add it before
  65  *
  66  * Insert a new entry before the specified head.
  67  * This is useful for implementing queues.
  68  */
  69 static inline void list_add_tail(struct list_head *new, struct list_head *head)
  70 {
  71         __list_add(new, head->prev, head);
  72 }
  73
  74 /*
  75  * Delete a list entry by making the prev/next entries
  76  * point to each other.
  77  *
  78  * This is only for internal list manipulation where we know
  79  * the prev/next entries already!
  80  */
  81 static inline void __list_del(struct list_head *prev, struct list_head *next)
  82 {
  83         next->prev = prev;
  84         prev->next = next;
  85 }
  86
  87 /**
  88  * list_del - deletes entry from list.
  89  * @entry: the element to delete from the list.
  90  * Note: list_empty on entry does not return true after this, the entry is in an undefined state.
  91  */
  92 static inline void list_del(struct list_head *entry)
  93 {
  94         __list_del(entry->prev, entry->next);
  95         entry->next = (void *) 0;
  96         entry->prev = (void *) 0;
  97 }
  98
  99 /**
 100  * list_del_init - deletes entry from list and reinitialize it.
 101  * @entry: the element to delete from the list.
 102  */
 103 static inline void list_del_init(struct list_head *entry)
 104 {
 105         __list_del(entry->prev, entry->next);
 106         INIT_LIST_HEAD(entry);
 107 }
 108
 109 /**
 110  * list_move - delete from one list and add as another's head
 111  * @list: the entry to move
 112  * @head: the head that will precede our entry
 113  */
 114 static inline void list_move(struct list_head *list, struct list_head *head)
 115 {
 116         __list_del(list->prev, list->next);
 117         list_add(list, head);
 118 }
 119
 120 /**
 121  * list_move_tail - delete from one list and add as another's tail
 122  * @list: the entry to move
 123  * @head: the head that will follow our entry
 124  */
 125 static inline void list_move_tail(struct list_head *list,
 126                                   struct list_head *head)
 127 {
 128         __list_del(list->prev, list->next);
 129         list_add_tail(list, head);
 130 }
 131
 132 /**
 133  * list_empty - tests whether a list is empty
 134  * @head: the list to test.
 135  */
 136 static inline int list_empty(struct list_head *head)
 137 {
 138         return head->next == head;
 139 }
 140
 141 static inline void __list_splice(struct list_head *list,
 142                                  struct list_head *head)
 143 {
 144         struct list_head *first = list->next;
 145         struct list_head *last = list->prev;
 146         struct list_head *at = head->next;
 147
 148         first->prev = head;
 149         head->next = first;
 150
 151         last->next = at;
 152         at->prev = last;
 153 }
 154
 155 /**
 156  * list_splice - join two lists
 157  * @list: the new list to add.
 158  * @head: the place to add it in the first list.
 159  */
 160 static inline void list_splice(struct list_head *list, struct list_head *head)
 161 {
 162         if (!list_empty(list))
 163                 __list_splice(list, head);
 164 }
 165
 166 /**
 167  * list_splice_init - join two lists and reinitialise the emptied list.
 168  * @list: the new list to add.
 169  * @head: the place to add it in the first list.
 170  *
 171  * The list at @list is reinitialised
 172  */
 173 static inline void list_splice_init(struct list_head *list,
 174                                     struct list_head *head)
 175 {
 176         if (!list_empty(list)) {
 177                 __list_splice(list, head);
 178                 INIT_LIST_HEAD(list);
 179         }
 180 }
 181
 182 /**
 183  * list_entry - get the struct for this entry
 184  * @ptr:        the &struct list_head pointer.
 185  * @type:       the type of the struct this is embedded in.
 186  * @member:     the name of the list_struct within the struct.
 187  */
 188 #define list_entry(ptr, type, member) \
 189         ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))
 190
 191 /**
 192  * list_for_each        -       iterate over a list
 193  * @pos:        the &struct list_head to use as a loop counter.
 194  * @head:       the head for your list.
 195  */
 196 #define list_for_each(pos, head) \
 197         for (pos = (head)->next, prefetch(pos->next); pos != (head); \
 198                 pos = pos->next, prefetch(pos->next))
 199 /**
 200  * list_for_each_prev   -       iterate over a list backwards
 201  * @pos:        the &struct list_head to use as a loop counter.
 202  * @head:       the head for your list.
 203  */
 204 #define list_for_each_prev(pos, head) \
 205         for (pos = (head)->prev, prefetch(pos->prev); pos != (head); \
 206                 pos = pos->prev, prefetch(pos->prev))
 207
 208 /**
 209  * list_for_each_safe   -       iterate over a list safe against removal of list entry
 210  * @pos:        the &struct list_head to use as a loop counter.
 211  * @n:          another &struct list_head to use as temporary storage
 212  * @head:       the head for your list.
 213  */
 214 #define list_for_each_safe(pos, n, head) \
 215         for (pos = (head)->next, n = pos->next; pos != (head); \
 216                 pos = n, n = pos->next)
 217
 218 /**
 219  * list_for_each_entry  -       iterate over list of given type
 220  * @pos:        the type * to use as a loop counter.
 221  * @head:       the head for your list.
 222  * @member:     the name of the list_struct within the struct.
 223  */
 224 #define list_for_each_entry(pos, head, member)                          \
 225         for (pos = list_entry((head)->next, typeof(*pos), member),      \
 226                      prefetch(pos->member.next);                        \
 227              &pos->member != (head);                                    \
 228              pos = list_entry(pos->member.next, typeof(*pos), member),  \
 229                      prefetch(pos->member.next))
 230
 231 /**
 232  * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 233  * @pos:        the type * to use as a loop counter.
 234  * @n:          another type * to use as temporary storage
 235  * @head:       the head for your list.
 236  * @member:     the name of the list_struct within the struct.
 237  */
 238 #define list_for_each_entry_safe(pos, n, head, member)                  \
 239         for (pos = list_entry((head)->next, typeof(*pos), member),      \
 240                 n = list_entry(pos->member.next, typeof(*pos), member); \
 241              &pos->member != (head);                                    \
 242              pos = n, n = list_entry(n->member.next, typeof(*n), member))
 243
 244 /**
 245  * list_for_each_entry_continue -       iterate over list of given type
 246  *                      continuing after existing point
 247  * @pos:        the type * to use as a loop counter.
 248  * @head:       the head for your list.
 249  * @member:     the name of the list_struct within the struct.
 250  */
 251 #define list_for_each_entry_continue(pos, head, member)                 \
 252         for (pos = list_entry(pos->member.next, typeof(*pos), member),  \
 253                      prefetch(pos->member.next);                        \
 254              &pos->member != (head);                                    \
 255              pos = list_entry(pos->member.next, typeof(*pos), member),  \
 256                      prefetch(pos->member.next))
 257
 258 #endif