include/linux/plist.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * Descending-priority-sorted double-linked list
   4  *
   5  * (C) 2002-2003 Intel Corp
   6  * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
   7  *
   8  * 2001-2005 (c) MontaVista Software, Inc.
   9  * Daniel Walker <dwalker@mvista.com>
  10  *
  11  * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
  12  *
  13  * Simplifications of the original code by
  14  * Oleg Nesterov <oleg@tv-sign.ru>
  15  *
  16  * Based on simple lists (include/linux/list.h).
  17  *
  18  * This is a priority-sorted list of nodes; each node has a
  19  * priority from INT_MIN (highest) to INT_MAX (lowest).
  20  *
  21  * Addition is O(K), removal is O(1), change of priority of a node is
  22  * O(K) and K is the number of RT priority levels used in the system.
  23  * (1 <= K <= 99)
  24  *
  25  * This list is really a list of lists:
  26  *
  27  *  - The tier 1 list is the prio_list, different priority nodes.
  28  *
  29  *  - The tier 2 list is the node_list, serialized nodes.
  30  *
  31  * Simple ASCII art explanation:
  32  *
  33  * pl:prio_list (only for plist_node)
  34  * nl:node_list
  35  *   HEAD|             NODE(S)
  36  *       |
  37  *       ||------------------------------------|
  38  *       ||->|pl|<->|pl|<--------------->|pl|<-|
  39  *       |   |10|   |21|   |21|   |21|   |40|   (prio)
  40  *       |   |  |   |  |   |  |   |  |   |  |
  41  *       |   |  |   |  |   |  |   |  |   |  |
  42  * |->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
  43  * |-------------------------------------------|
  44  *
  45  * The nodes on the prio_list list are sorted by priority to simplify
  46  * the insertion of new nodes. There are no nodes with duplicate
  47  * priorites on the list.
  48  *
  49  * The nodes on the node_list are ordered by priority and can contain
  50  * entries which have the same priority. Those entries are ordered
  51  * FIFO
  52  *
  53  * Addition means: look for the prio_list node in the prio_list
  54  * for the priority of the node and insert it before the node_list
  55  * entry of the next prio_list node. If it is the first node of
  56  * that priority, add it to the prio_list in the right position and
  57  * insert it into the serialized node_list list
  58  *
  59  * Removal means remove it from the node_list and remove it from
  60  * the prio_list if the node_list list_head is non empty. In case
  61  * of removal from the prio_list it must be checked whether other
  62  * entries of the same priority are on the list or not. If there
  63  * is another entry of the same priority then this entry has to
  64  * replace the removed entry on the prio_list. If the entry which
  65  * is removed is the only entry of this priority then a simple
  66  * remove from both list is sufficient.
  67  *
  68  * INT_MIN is the highest priority, 0 is the medium highest, INT_MAX
  69  * is lowest priority.
  70  *
  71  * No locking is done, up to the caller.
  72  */
  73 #ifndef _LINUX_PLIST_H_
  74 #define _LINUX_PLIST_H_
  75
  76 #include <linux/kernel.h>
  77 #include <linux/list.h>
  78
  79 struct plist_head {
  80         struct list_head node_list;
  81 };
  82
  83 struct plist_node {
  84         int                     prio;
  85         struct list_head        prio_list;
  86         struct list_head        node_list;
  87 };
  88
  89 /**
  90  * PLIST_HEAD_INIT - static struct plist_head initializer
  91  * @head:       struct plist_head variable name
  92  */
  93 #define PLIST_HEAD_INIT(head)                           \
  94 {                                                       \
  95         .node_list = LIST_HEAD_INIT((head).node_list)   \
  96 }
  97
  98 /**
  99  * PLIST_HEAD - declare and init plist_head
 100  * @head:       name for struct plist_head variable
 101  */
 102 #define PLIST_HEAD(head) \
 103         struct plist_head head = PLIST_HEAD_INIT(head)
 104
 105 /**
 106  * PLIST_NODE_INIT - static struct plist_node initializer
 107  * @node:       struct plist_node variable name
 108  * @__prio:     initial node priority
 109  */
 110 #define PLIST_NODE_INIT(node, __prio)                   \
 111 {                                                       \
 112         .prio  = (__prio),                              \
 113         .prio_list = LIST_HEAD_INIT((node).prio_list),  \
 114         .node_list = LIST_HEAD_INIT((node).node_list),  \
 115 }
 116
 117 /**
 118  * plist_head_init - dynamic struct plist_head initializer
 119  * @head:       &struct plist_head pointer
 120  */
 121 static inline void
 122 plist_head_init(struct plist_head *head)
 123 {
 124         INIT_LIST_HEAD(&head->node_list);
 125 }
 126
 127 /**
 128  * plist_node_init - Dynamic struct plist_node initializer
 129  * @node:       &struct plist_node pointer
 130  * @prio:       initial node priority
 131  */
 132 static inline void plist_node_init(struct plist_node *node, int prio)
 133 {
 134         node->prio = prio;
 135         INIT_LIST_HEAD(&node->prio_list);
 136         INIT_LIST_HEAD(&node->node_list);
 137 }
 138
 139 extern void plist_add(struct plist_node *node, struct plist_head *head);
 140 extern void plist_del(struct plist_node *node, struct plist_head *head);
 141
 142 extern void plist_requeue(struct plist_node *node, struct plist_head *head);
 143
 144 /**
 145  * plist_for_each - iterate over the plist
 146  * @pos:        the type * to use as a loop counter
 147  * @head:       the head for your list
 148  */
 149 #define plist_for_each(pos, head)       \
 150          list_for_each_entry(pos, &(head)->node_list, node_list)
 151
 152 /**
 153  * plist_for_each_continue - continue iteration over the plist
 154  * @pos:        the type * to use as a loop cursor
 155  * @head:       the head for your list
 156  *
 157  * Continue to iterate over plist, continuing after the current position.
 158  */
 159 #define plist_for_each_continue(pos, head)      \
 160          list_for_each_entry_continue(pos, &(head)->node_list, 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, 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_head within the struct
 178  */
 179 #define plist_for_each_entry(pos, head, mem)    \
 180          list_for_each_entry(pos, &(head)->node_list, mem.node_list)
 181
 182 /**
 183  * plist_for_each_entry_continue - continue iteration over list of given type
 184  * @pos:        the type * to use as a loop cursor
 185  * @head:       the head for your list
 186  * @m:          the name of the list_head within the struct
 187  *
 188  * Continue to iterate over list of given type, continuing after
 189  * the current position.
 190  */
 191 #define plist_for_each_entry_continue(pos, head, m)     \
 192         list_for_each_entry_continue(pos, &(head)->node_list, m.node_list)
 193
 194 /**
 195  * plist_for_each_entry_safe - iterate safely over list 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  * @m:          the name of the list_head within the struct
 200  *
 201  * Iterate over list of given type, safe against removal of list entry.
 202  */
 203 #define plist_for_each_entry_safe(pos, n, head, m)      \
 204         list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)
 205
 206 /**
 207  * plist_head_empty - return !0 if a plist_head is empty
 208  * @head:       &struct plist_head pointer
 209  */
 210 static inline int plist_head_empty(const struct plist_head *head)
 211 {
 212         return list_empty(&head->node_list);
 213 }
 214
 215 /**
 216  * plist_node_empty - return !0 if plist_node is not on a list
 217  * @node:       &struct plist_node pointer
 218  */
 219 static inline int plist_node_empty(const struct plist_node *node)
 220 {
 221         return list_empty(&node->node_list);
 222 }
 223
 224 /* All functions below assume the plist_head is not empty. */
 225
 226 /**
 227  * plist_first_entry - get the struct for the first entry
 228  * @head:       the &struct plist_head pointer
 229  * @type:       the type of the struct this is embedded in
 230  * @member:     the name of the list_head within the struct
 231  */
 232 #ifdef CONFIG_DEBUG_PLIST
 233 # define plist_first_entry(head, type, member)  \
 234 ({ \
 235         WARN_ON(plist_head_empty(head)); \
 236         container_of(plist_first(head), type, member); \
 237 })
 238 #else
 239 # define plist_first_entry(head, type, member)  \
 240         container_of(plist_first(head), type, member)
 241 #endif
 242
 243 /**
 244  * plist_last_entry - get the struct for the last entry
 245  * @head:       the &struct plist_head pointer
 246  * @type:       the type of the struct this is embedded in
 247  * @member:     the name of the list_head within the struct
 248  */
 249 #ifdef CONFIG_DEBUG_PLIST
 250 # define plist_last_entry(head, type, member)   \
 251 ({ \
 252         WARN_ON(plist_head_empty(head)); \
 253         container_of(plist_last(head), type, member); \
 254 })
 255 #else
 256 # define plist_last_entry(head, type, member)   \
 257         container_of(plist_last(head), type, member)
 258 #endif
 259
 260 /**
 261  * plist_next - get the next entry in list
 262  * @pos:        the type * to cursor
 263  */
 264 #define plist_next(pos) \
 265         list_next_entry(pos, node_list)
 266
 267 /**
 268  * plist_prev - get the prev entry in list
 269  * @pos:        the type * to cursor
 270  */
 271 #define plist_prev(pos) \
 272         list_prev_entry(pos, node_list)
 273
 274 /**
 275  * plist_first - return the first node (and thus, highest priority)
 276  * @head:       the &struct plist_head pointer
 277  *
 278  * Assumes the plist is _not_ empty.
 279  */
 280 static inline struct plist_node *plist_first(const struct plist_head *head)
 281 {
 282         return list_entry(head->node_list.next,
 283                           struct plist_node, node_list);
 284 }
 285
 286 /**
 287  * plist_last - return the last node (and thus, lowest priority)
 288  * @head:       the &struct plist_head pointer
 289  *
 290  * Assumes the plist is _not_ empty.
 291  */
 292 static inline struct plist_node *plist_last(const struct plist_head *head)
 293 {
 294         return list_entry(head->node_list.prev,
 295                           struct plist_node, node_list);
 296 }
 297
 298 #endif