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/types.h>
79
80#include <asm/bug.h>
81
82struct plist_head {
83 struct list_head node_list;
84};
85
86struct plist_node {
87 int prio;
88 struct list_head prio_list;
89 struct list_head node_list;
90};
91
92/**
93 * PLIST_HEAD_INIT - static struct plist_head initializer
94 * @head: struct plist_head variable name
95 */
96#define PLIST_HEAD_INIT(head) \
97{ \
98 .node_list = LIST_HEAD_INIT((head).node_list) \
99}
100
101/**
102 * PLIST_HEAD - declare and init plist_head
103 * @head: name for struct plist_head variable
104 */
105#define PLIST_HEAD(head) \
106 struct plist_head head = PLIST_HEAD_INIT(head)
107
108/**
109 * PLIST_NODE_INIT - static struct plist_node initializer
110 * @node: struct plist_node variable name
111 * @__prio: initial node priority
112 */
113#define PLIST_NODE_INIT(node, __prio) \
114{ \
115 .prio = (__prio), \
116 .prio_list = LIST_HEAD_INIT((node).prio_list), \
117 .node_list = LIST_HEAD_INIT((node).node_list), \
118}
119
120/**
121 * plist_head_init - dynamic struct plist_head initializer
122 * @head: &struct plist_head pointer
123 */
124static inline void
125plist_head_init(struct plist_head *head)
126{
127 INIT_LIST_HEAD(&head->node_list);
128}
129
130/**
131 * plist_node_init - Dynamic struct plist_node initializer
132 * @node: &struct plist_node pointer
133 * @prio: initial node priority
134 */
135static inline void plist_node_init(struct plist_node *node, int prio)
136{
137 node->prio = prio;
138 INIT_LIST_HEAD(&node->prio_list);
139 INIT_LIST_HEAD(&node->node_list);
140}
141
142extern void plist_add(struct plist_node *node, struct plist_head *head);
143extern void plist_del(struct plist_node *node, struct plist_head *head);
144
145extern void plist_requeue(struct plist_node *node, struct plist_head *head);
146
147/**
148 * plist_for_each - iterate over the plist
149 * @pos: the type * to use as a loop counter
150 * @head: the head for your list
151 */
152#define plist_for_each(pos, head) \
153 list_for_each_entry(pos, &(head)->node_list, node_list)
154
155/**
156 * plist_for_each_continue - continue iteration over the plist
157 * @pos: the type * to use as a loop cursor
158 * @head: the head for your list
159 *
160 * Continue to iterate over plist, continuing after the current position.
161 */
162#define plist_for_each_continue(pos, head) \
163 list_for_each_entry_continue(pos, &(head)->node_list, node_list)
164
165/**
166 * plist_for_each_safe - iterate safely over a plist of given type
167 * @pos: the type * to use as a loop counter
168 * @n: another type * to use as temporary storage
169 * @head: the head for your list
170 *
171 * Iterate over a plist of given type, safe against removal of list entry.
172 */
173#define plist_for_each_safe(pos, n, head) \
174 list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)
175
176/**
177 * plist_for_each_entry - iterate over list of given type
178 * @pos: the type * to use as a loop counter
179 * @head: the head for your list
180 * @mem: the name of the list_head within the struct
181 */
182#define plist_for_each_entry(pos, head, mem) \
183 list_for_each_entry(pos, &(head)->node_list, mem.node_list)
184
185/**
186 * plist_for_each_entry_continue - continue iteration over list of given type
187 * @pos: the type * to use as a loop cursor
188 * @head: the head for your list
189 * @m: the name of the list_head within the struct
190 *
191 * Continue to iterate over list of given type, continuing after
192 * the current position.
193 */
194#define plist_for_each_entry_continue(pos, head, m) \
195 list_for_each_entry_continue(pos, &(head)->node_list, m.node_list)
196
197/**
198 * plist_for_each_entry_safe - iterate safely over list of given type
199 * @pos: the type * to use as a loop counter
200 * @n: another type * to use as temporary storage
201 * @head: the head for your list
202 * @m: the name of the list_head within the struct
203 *
204 * Iterate over list of given type, safe against removal of list entry.
205 */
206#define plist_for_each_entry_safe(pos, n, head, m) \
207 list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)
208
209/**
210 * plist_head_empty - return !0 if a plist_head is empty
211 * @head: &struct plist_head pointer
212 */
213static inline int plist_head_empty(const struct plist_head *head)
214{
215 return list_empty(&head->node_list);
216}
217
218/**
219 * plist_node_empty - return !0 if plist_node is not on a list
220 * @node: &struct plist_node pointer
221 */
222static inline int plist_node_empty(const struct plist_node *node)
223{
224 return list_empty(&node->node_list);
225}
226
227/* All functions below assume the plist_head is not empty. */
228
229/**
230 * plist_first_entry - get the struct for the first entry
231 * @head: the &struct plist_head pointer
232 * @type: the type of the struct this is embedded in
233 * @member: the name of the list_head within the struct
234 */
235#ifdef CONFIG_DEBUG_PLIST
236# define plist_first_entry(head, type, member) \
237({ \
238 WARN_ON(plist_head_empty(head)); \
239 container_of(plist_first(head), type, member); \
240})
241#else
242# define plist_first_entry(head, type, member) \
243 container_of(plist_first(head), type, member)
244#endif
245
246/**
247 * plist_last_entry - get the struct for the last 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_head within the struct
251 */
252#ifdef CONFIG_DEBUG_PLIST
253# define plist_last_entry(head, type, member) \
254({ \
255 WARN_ON(plist_head_empty(head)); \
256 container_of(plist_last(head), type, member); \
257})
258#else
259# define plist_last_entry(head, type, member) \
260 container_of(plist_last(head), type, member)
261#endif
262
263/**
264 * plist_next - get the next entry in list
265 * @pos: the type * to cursor
266 */
267#define plist_next(pos) \
268 list_next_entry(pos, node_list)
269
270/**
271 * plist_prev - get the prev entry in list
272 * @pos: the type * to cursor
273 */
274#define plist_prev(pos) \
275 list_prev_entry(pos, node_list)
276
277/**
278 * plist_first - return the first node (and thus, highest priority)
279 * @head: the &struct plist_head pointer
280 *
281 * Assumes the plist is _not_ empty.
282 */
283static inline struct plist_node *plist_first(const struct plist_head *head)
284{
285 return list_entry(head->node_list.next,
286 struct plist_node, node_list);
287}
288
289/**
290 * plist_last - return the last node (and thus, lowest priority)
291 * @head: the &struct plist_head pointer
292 *
293 * Assumes the plist is _not_ empty.
294 */
295static inline struct plist_node *plist_last(const struct plist_head *head)
296{
297 return list_entry(head->node_list.prev,
298 struct plist_node, node_list);
299}
300
301#endif
302

source code of linux/include/linux/plist.h