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 #include <linux/spinlock_types.h>
  81
  82 struct plist_head {
  83         struct list_head node_list;
  84 #ifdef CONFIG_DEBUG_PI_LIST
  85         raw_spinlock_t *rawlock;
  86         spinlock_t *spinlock;
  87 #endif
  88 };
  89
  90 struct plist_node {
  91         int                     prio;
  92         struct list_head        prio_list;
  93         struct list_head        node_list;
  94 };
  95
  96 #ifdef CONFIG_DEBUG_PI_LIST
  97 # define PLIST_HEAD_LOCK_INIT(_lock)            .spinlock = _lock
  98 # define PLIST_HEAD_LOCK_INIT_RAW(_lock)        .rawlock = _lock
  99 #else
 100 # define PLIST_HEAD_LOCK_INIT(_lock)
 101 # define PLIST_HEAD_LOCK_INIT_RAW(_lock)
 102 #endif
 103
 104 #define _PLIST_HEAD_INIT(head)                          \
 105         .node_list = LIST_HEAD_INIT((head).node_list)
 106
 107 /**
 108  * PLIST_HEAD_INIT - static struct plist_head initializer
 109  * @head:       struct plist_head variable name
 110  * @_lock:      lock to initialize for this list
 111  */
 112 #define PLIST_HEAD_INIT(head, _lock)                    \
 113 {                                                       \
 114         _PLIST_HEAD_INIT(head),                         \
 115         PLIST_HEAD_LOCK_INIT(&(_lock))                  \
 116 }
 117
 118 /**
 119  * PLIST_HEAD_INIT_RAW - static struct plist_head initializer
 120  * @head:       struct plist_head variable name
 121  * @_lock:      lock to initialize for this list
 122  */
 123 #define PLIST_HEAD_INIT_RAW(head, _lock)                \
 124 {                                                       \
 125         _PLIST_HEAD_INIT(head),                         \
 126         PLIST_HEAD_LOCK_INIT_RAW(&(_lock))              \
 127 }
 128
 129 /**
 130  * PLIST_NODE_INIT - static struct plist_node initializer
 131  * @node:       struct plist_node variable name
 132  * @__prio:     initial node priority
 133  */
 134 #define PLIST_NODE_INIT(node, __prio)                   \
 135 {                                                       \
 136         .prio  = (__prio),                              \
 137         .prio_list = LIST_HEAD_INIT((node).prio_list),  \
 138         .node_list = LIST_HEAD_INIT((node).node_list),  \
 139 }
 140
 141 /**
 142  * plist_head_init - dynamic struct plist_head initializer
 143  * @head:       &struct plist_head pointer
 144  * @lock:       spinlock protecting the list (debugging)
 145  */
 146 static inline void
 147 plist_head_init(struct plist_head *head, spinlock_t *lock)
 148 {
 149         INIT_LIST_HEAD(&head->node_list);
 150 #ifdef CONFIG_DEBUG_PI_LIST
 151         head->spinlock = lock;
 152         head->rawlock = NULL;
 153 #endif
 154 }
 155
 156 /**
 157  * plist_head_init_raw - dynamic struct plist_head initializer
 158  * @head:       &struct plist_head pointer
 159  * @lock:       raw_spinlock protecting the list (debugging)
 160  */
 161 static inline void
 162 plist_head_init_raw(struct plist_head *head, raw_spinlock_t *lock)
 163 {
 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         INIT_LIST_HEAD(&node->prio_list);
 180         INIT_LIST_HEAD(&node->node_list);
 181 }
 182
 183 extern void plist_add(struct plist_node *node, struct plist_head *head);
 184 extern void plist_del(struct plist_node *node, struct plist_head *head);
 185
 186 /**
 187  * plist_for_each - iterate over the plist
 188  * @pos:        the type * to use as a loop counter
 189  * @head:       the head for your list
 190  */
 191 #define plist_for_each(pos, head)       \
 192          list_for_each_entry(pos, &(head)->node_list, node_list)
 193
 194 /**
 195  * plist_for_each_safe - iterate safely over a plist of given type
 196  * @pos:        the type * to use as a loop counter
 197  * @n:  another type * to use as temporary storage
 198  * @head:       the head for your list
 199  *
 200  * Iterate over a plist of given type, safe against removal of list entry.
 201  */
 202 #define plist_for_each_safe(pos, n, head)       \
 203          list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)
 204
 205 /**
 206  * plist_for_each_entry - iterate over list of given type
 207  * @pos:        the type * to use as a loop counter
 208  * @head:       the head for your list
 209  * @mem:        the name of the list_struct within the struct
 210  */
 211 #define plist_for_each_entry(pos, head, mem)    \
 212          list_for_each_entry(pos, &(head)->node_list, mem.node_list)
 213
 214 /**
 215  * plist_for_each_entry_safe - iterate safely over list of given type
 216  * @pos:        the type * to use as a loop counter
 217  * @n:          another type * to use as temporary storage
 218  * @head:       the head for your list
 219  * @m:          the name of the list_struct within the struct
 220  *
 221  * Iterate over list of given type, safe against removal of list entry.
 222  */
 223 #define plist_for_each_entry_safe(pos, n, head, m)      \
 224         list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)
 225
 226 /**
 227  * plist_head_empty - return !0 if a plist_head is empty
 228  * @head:       &struct plist_head pointer
 229  */
 230 static inline int plist_head_empty(const struct plist_head *head)
 231 {
 232         return list_empty(&head->node_list);
 233 }
 234
 235 /**
 236  * plist_node_empty - return !0 if plist_node is not on a list
 237  * @node:       &struct plist_node pointer
 238  */
 239 static inline int plist_node_empty(const struct plist_node *node)
 240 {
 241         return list_empty(&node->node_list);
 242 }
 243
 244 /* All functions below assume the plist_head is not empty. */
 245
 246 /**
 247  * plist_first_entry - get the struct for the first entry
 248  * @head:       the &struct plist_head pointer
 249  * @type:       the type of the struct this is embedded in
 250  * @member:     the name of the list_struct within the struct
 251  */
 252 #ifdef CONFIG_DEBUG_PI_LIST
 253 # define plist_first_entry(head, type, member)  \
 254 ({ \
 255         WARN_ON(plist_head_empty(head)); \
 256         container_of(plist_first(head), type, member); \
 257 })
 258 #else
 259 # define plist_first_entry(head, type, member)  \
 260         container_of(plist_first(head), type, member)
 261 #endif
 262
 263 /**
 264  * plist_last_entry - get the struct for the last entry
 265  * @head:       the &struct plist_head pointer
 266  * @type:       the type of the struct this is embedded in
 267  * @member:     the name of the list_struct within the struct
 268  */
 269 #ifdef CONFIG_DEBUG_PI_LIST
 270 # define plist_last_entry(head, type, member)   \
 271 ({ \
 272         WARN_ON(plist_head_empty(head)); \
 273         container_of(plist_last(head), type, member); \
 274 })
 275 #else
 276 # define plist_last_entry(head, type, member)   \
 277         container_of(plist_last(head), type, member)
 278 #endif
 279
 280 /**
 281  * plist_first - return the first node (and thus, highest priority)
 282  * @head:       the &struct plist_head pointer
 283  *
 284  * Assumes the plist is _not_ empty.
 285  */
 286 static inline struct plist_node *plist_first(const struct plist_head *head)
 287 {
 288         return list_entry(head->node_list.next,
 289                           struct plist_node, node_list);
 290 }
 291
 292 /**
 293  * plist_last - return the last node (and thus, lowest priority)
 294  * @head:       the &struct plist_head pointer
 295  *
 296  * Assumes the plist is _not_ empty.
 297  */
 298 static inline struct plist_node *plist_last(const struct plist_head *head)
 299 {
 300         return list_entry(head->node_list.prev,
 301                           struct plist_node, node_list);
 302 }
 303
 304 #endif