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/container_of.h>
  77 #include <linux/list.h>
  78 #include <linux/plist_types.h>
  79
  80 #include <asm/bug.h>
  81
  82 /**
  83  * PLIST_HEAD_INIT - static struct plist_head initializer
  84  * @head:       struct plist_head variable name
  85  */
  86 #define PLIST_HEAD_INIT(head)                           \
  87 {                                                       \
  88         .node_list = LIST_HEAD_INIT((head).node_list)   \
  89 }
  90
  91 /**
  92  * PLIST_HEAD - declare and init plist_head
  93  * @head:       name for struct plist_head variable
  94  */
  95 #define PLIST_HEAD(head) \
  96         struct plist_head head = PLIST_HEAD_INIT(head)
  97
  98 /**
  99  * PLIST_NODE_INIT - static struct plist_node initializer
 100  * @node:       struct plist_node variable name
 101  * @__prio:     initial node priority
 102  */
 103 #define PLIST_NODE_INIT(node, __prio)                   \
 104 {                                                       \
 105         .prio  = (__prio),                              \
 106         .prio_list = LIST_HEAD_INIT((node).prio_list),  \
 107         .node_list = LIST_HEAD_INIT((node).node_list),  \
 108 }
 109
 110 /**
 111  * plist_head_init - dynamic struct plist_head initializer
 112  * @head:       &struct plist_head pointer
 113  */
 114 static inline void
 115 plist_head_init(struct plist_head *head)
 116 {
 117         INIT_LIST_HEAD(&head->node_list);
 118 }
 119
 120 /**
 121  * plist_node_init - Dynamic struct plist_node initializer
 122  * @node:       &struct plist_node pointer
 123  * @prio:       initial node priority
 124  */
 125 static inline void plist_node_init(struct plist_node *node, int prio)
 126 {
 127         node->prio = prio;
 128         INIT_LIST_HEAD(&node->prio_list);
 129         INIT_LIST_HEAD(&node->node_list);
 130 }
 131
 132 extern void plist_add(struct plist_node *node, struct plist_head *head);
 133 extern void plist_del(struct plist_node *node, struct plist_head *head);
 134
 135 extern void plist_requeue(struct plist_node *node, struct plist_head *head);
 136
 137 /**
 138  * plist_for_each - iterate over the plist
 139  * @pos:        the type * to use as a loop counter
 140  * @head:       the head for your list
 141  */
 142 #define plist_for_each(pos, head)       \
 143          list_for_each_entry(pos, &(head)->node_list, node_list)
 144
 145 /**
 146  * plist_for_each_continue - continue iteration over the plist
 147  * @pos:        the type * to use as a loop cursor
 148  * @head:       the head for your list
 149  *
 150  * Continue to iterate over plist, continuing after the current position.
 151  */
 152 #define plist_for_each_continue(pos, head)      \
 153          list_for_each_entry_continue(pos, &(head)->node_list, node_list)
 154
 155 /**
 156  * plist_for_each_safe - iterate safely over a plist of given type
 157  * @pos:        the type * to use as a loop counter
 158  * @n:  another type * to use as temporary storage
 159  * @head:       the head for your list
 160  *
 161  * Iterate over a plist of given type, safe against removal of list entry.
 162  */
 163 #define plist_for_each_safe(pos, n, head)       \
 164          list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)
 165
 166 /**
 167  * plist_for_each_entry - iterate over list of given type
 168  * @pos:        the type * to use as a loop counter
 169  * @head:       the head for your list
 170  * @mem:        the name of the list_head within the struct
 171  */
 172 #define plist_for_each_entry(pos, head, mem)    \
 173          list_for_each_entry(pos, &(head)->node_list, mem.node_list)
 174
 175 /**
 176  * plist_for_each_entry_continue - continue iteration over list of given type
 177  * @pos:        the type * to use as a loop cursor
 178  * @head:       the head for your list
 179  * @m:          the name of the list_head within the struct
 180  *
 181  * Continue to iterate over list of given type, continuing after
 182  * the current position.
 183  */
 184 #define plist_for_each_entry_continue(pos, head, m)     \
 185         list_for_each_entry_continue(pos, &(head)->node_list, m.node_list)
 186
 187 /**
 188  * plist_for_each_entry_safe - iterate safely over list of given type
 189  * @pos:        the type * to use as a loop counter
 190  * @n:          another type * to use as temporary storage
 191  * @head:       the head for your list
 192  * @m:          the name of the list_head within the struct
 193  *
 194  * Iterate over list of given type, safe against removal of list entry.
 195  */
 196 #define plist_for_each_entry_safe(pos, n, head, m)      \
 197         list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)
 198
 199 /**
 200  * plist_head_empty - return !0 if a plist_head is empty
 201  * @head:       &struct plist_head pointer
 202  */
 203 static inline int plist_head_empty(const struct plist_head *head)
 204 {
 205         return list_empty(&head->node_list);
 206 }
 207
 208 /**
 209  * plist_node_empty - return !0 if plist_node is not on a list
 210  * @node:       &struct plist_node pointer
 211  */
 212 static inline int plist_node_empty(const struct plist_node *node)
 213 {
 214         return list_empty(&node->node_list);
 215 }
 216
 217 /* All functions below assume the plist_head is not empty. */
 218
 219 /**
 220  * plist_first_entry - get the struct for the first entry
 221  * @head:       the &struct plist_head pointer
 222  * @type:       the type of the struct this is embedded in
 223  * @member:     the name of the list_head within the struct
 224  */
 225 #ifdef CONFIG_DEBUG_PLIST
 226 # define plist_first_entry(head, type, member)  \
 227 ({ \
 228         WARN_ON(plist_head_empty(head)); \
 229         container_of(plist_first(head), type, member); \
 230 })
 231 #else
 232 # define plist_first_entry(head, type, member)  \
 233         container_of(plist_first(head), type, member)
 234 #endif
 235
 236 /**
 237  * plist_last_entry - get the struct for the last entry
 238  * @head:       the &struct plist_head pointer
 239  * @type:       the type of the struct this is embedded in
 240  * @member:     the name of the list_head within the struct
 241  */
 242 #ifdef CONFIG_DEBUG_PLIST
 243 # define plist_last_entry(head, type, member)   \
 244 ({ \
 245         WARN_ON(plist_head_empty(head)); \
 246         container_of(plist_last(head), type, member); \
 247 })
 248 #else
 249 # define plist_last_entry(head, type, member)   \
 250         container_of(plist_last(head), type, member)
 251 #endif
 252
 253 /**
 254  * plist_next - get the next entry in list
 255  * @pos:        the type * to cursor
 256  */
 257 #define plist_next(pos) \
 258         list_next_entry(pos, node_list)
 259
 260 /**
 261  * plist_prev - get the prev entry in list
 262  * @pos:        the type * to cursor
 263  */
 264 #define plist_prev(pos) \
 265         list_prev_entry(pos, node_list)
 266
 267 /**
 268  * plist_first - return the first node (and thus, highest priority)
 269  * @head:       the &struct plist_head pointer
 270  *
 271  * Assumes the plist is _not_ empty.
 272  */
 273 static inline struct plist_node *plist_first(const struct plist_head *head)
 274 {
 275         return list_entry(head->node_list.next,
 276                           struct plist_node, node_list);
 277 }
 278
 279 /**
 280  * plist_last - return the last node (and thus, lowest priority)
 281  * @head:       the &struct plist_head pointer
 282  *
 283  * Assumes the plist is _not_ empty.
 284  */
 285 static inline struct plist_node *plist_last(const struct plist_head *head)
 286 {
 287         return list_entry(head->node_list.prev,
 288                           struct plist_node, node_list);
 289 }
 290
 291 #endif