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         raw_spinlock_t *rawlock;
  85         spinlock_t *spinlock;
  86 #endif
  87 };
  88
  89 struct plist_node {
  90         int                     prio;
  91         struct plist_head       plist;
  92 };
  93
  94 #ifdef CONFIG_DEBUG_PI_LIST
  95 # define PLIST_HEAD_LOCK_INIT(_lock)            .spinlock = _lock
  96 # define PLIST_HEAD_LOCK_INIT_RAW(_lock)        .rawlock = _lock
  97 #else
  98 # define PLIST_HEAD_LOCK_INIT(_lock)
  99 # define PLIST_HEAD_LOCK_INIT_RAW(_lock)
 100 #endif
 101
 102 #define _PLIST_HEAD_INIT(head)                          \
 103         .prio_list = LIST_HEAD_INIT((head).prio_list),  \
 104         .node_list = LIST_HEAD_INIT((head).node_list)
 105
 106 /**
 107  * PLIST_HEAD_INIT - static struct plist_head initializer
 108  * @head:       struct plist_head variable name
 109  * @_lock:      lock to initialize for this list
 110  */
 111 #define PLIST_HEAD_INIT(head, _lock)                    \
 112 {                                                       \
 113         _PLIST_HEAD_INIT(head),                         \
 114         PLIST_HEAD_LOCK_INIT(&(_lock))                  \
 115 }
 116
 117 /**
 118  * PLIST_HEAD_INIT_RAW - static struct plist_head initializer
 119  * @head:       struct plist_head variable name
 120  * @_lock:      lock to initialize for this list
 121  */
 122 #define PLIST_HEAD_INIT_RAW(head, _lock)                \
 123 {                                                       \
 124         _PLIST_HEAD_INIT(head),                         \
 125         PLIST_HEAD_LOCK_INIT_RAW(&(_lock))              \
 126 }
 127
 128 /**
 129  * PLIST_NODE_INIT - static struct plist_node initializer
 130  * @node:       struct plist_node variable name
 131  * @__prio:     initial node priority
 132  */
 133 #define PLIST_NODE_INIT(node, __prio)                   \
 134 {                                                       \
 135         .prio  = (__prio),                              \
 136         .plist = { _PLIST_HEAD_INIT((node).plist) },    \
 137 }
 138
 139 /**
 140  * plist_head_init - dynamic struct plist_head initializer
 141  * @head:       &struct plist_head pointer
 142  * @lock:       spinlock protecting the list (debugging)
 143  */
 144 static inline void
 145 plist_head_init(struct plist_head *head, spinlock_t *lock)
 146 {
 147         INIT_LIST_HEAD(&head->prio_list);
 148         INIT_LIST_HEAD(&head->node_list);
 149 #ifdef CONFIG_DEBUG_PI_LIST
 150         head->spinlock = lock;
 151         head->rawlock = NULL;
 152 #endif
 153 }
 154
 155 /**
 156  * plist_head_init_raw - dynamic struct plist_head initializer
 157  * @head:       &struct plist_head pointer
 158  * @lock:       raw_spinlock protecting the list (debugging)
 159  */
 160 static inline void
 161 plist_head_init_raw(struct plist_head *head, raw_spinlock_t *lock)
 162 {
 163         INIT_LIST_HEAD(&head->prio_list);
 164         INIT_LIST_HEAD(&head->node_list);
 165 #ifdef CONFIG_DEBUG_PI_LIST
 166         head->rawlock = lock;
 167         head->spinlock = NULL;
 168 #endif
 169 }
 170
 171 /**
 172  * plist_node_init - Dynamic struct plist_node initializer
 173  * @node:       &struct plist_node pointer
 174  * @prio:       initial node priority
 175  */
 176 static inline void plist_node_init(struct plist_node *node, int prio)
 177 {
 178         node->prio = prio;
 179         plist_head_init(&node->plist, NULL);
 180 }
 181
 182 extern void plist_add(struct plist_node *node, struct plist_head *head);
 183 extern void plist_del(struct plist_node *node, struct plist_head *head);
 184
 185 /**
 186  * plist_for_each - iterate over the plist
 187  * @pos:        the type * to use as a loop counter
 188  * @head:       the head for your list
 189  */
 190 #define plist_for_each(pos, head)       \
 191          list_for_each_entry(pos, &(head)->node_list, plist.node_list)
 192
 193 /**
 194  * plist_for_each_safe - iterate safely over a plist of given type
 195  * @pos:        the type * to use as a loop counter
 196  * @n:  another type * to use as temporary storage
 197  * @head:       the head for your list
 198  *
 199  * Iterate over a plist of given type, safe against removal of list entry.
 200  */
 201 #define plist_for_each_safe(pos, n, head)       \
 202          list_for_each_entry_safe(pos, n, &(head)->node_list, plist.node_list)
 203
 204 /**
 205  * plist_for_each_entry - iterate over list of given type
 206  * @pos:        the type * to use as a loop counter
 207  * @head:       the head for your list
 208  * @mem:        the name of the list_struct within the struct
 209  */
 210 #define plist_for_each_entry(pos, head, mem)    \
 211          list_for_each_entry(pos, &(head)->node_list, mem.plist.node_list)
 212
 213 /**
 214  * plist_for_each_entry_safe - iterate safely over list of given type
 215  * @pos:        the type * to use as a loop counter
 216  * @n:          another type * to use as temporary storage
 217  * @head:       the head for your list
 218  * @m:          the name of the list_struct within the struct
 219  *
 220  * Iterate over list of given type, safe against removal of list entry.
 221  */
 222 #define plist_for_each_entry_safe(pos, n, head, m)      \
 223         list_for_each_entry_safe(pos, n, &(head)->node_list, m.plist.node_list)
 224
 225 /**
 226  * plist_head_empty - return !0 if a plist_head is empty
 227  * @head:       &struct plist_head pointer
 228  */
 229 static inline int plist_head_empty(const struct plist_head *head)
 230 {
 231         return list_empty(&head->node_list);
 232 }
 233
 234 /**
 235  * plist_node_empty - return !0 if plist_node is not on a list
 236  * @node:       &struct plist_node pointer
 237  */
 238 static inline int plist_node_empty(const struct plist_node *node)
 239 {
 240         return plist_head_empty(&node->plist);
 241 }
 242
 243 /* All functions below assume the plist_head is not empty. */
 244
 245 /**
 246  * plist_first_entry - get the struct for the first entry
 247  * @head:       the &struct plist_head pointer
 248  * @type:       the type of the struct this is embedded in
 249  * @member:     the name of the list_struct within the struct
 250  */
 251 #ifdef CONFIG_DEBUG_PI_LIST
 252 # define plist_first_entry(head, type, member)  \
 253 ({ \
 254         WARN_ON(plist_head_empty(head)); \
 255         container_of(plist_first(head), type, member); \
 256 })
 257 #else
 258 # define plist_first_entry(head, type, member)  \
 259         container_of(plist_first(head), type, member)
 260 #endif
 261
 262 /**
 263  * plist_first - return the first node (and thus, highest priority)
 264  * @head:       the &struct plist_head pointer
 265  *
 266  * Assumes the plist is _not_ empty.
 267  */
 268 static inline struct plist_node* plist_first(const struct plist_head *head)
 269 {
 270         return list_entry(head->node_list.next,
 271                           struct plist_node, plist.node_list);
 272 }
 273
 274 #endif