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 79struct plist_head { 80 struct list_head node_list; 81}; 82 83struct 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 */ 121static inline void 122plist_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 */ 132static 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 139extern void plist_add(struct plist_node *node, struct plist_head *head); 140extern void plist_del(struct plist_node *node, struct plist_head *head); 141 142extern 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 */ 210static 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 */ 219static 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 */ 280static 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 */ 292static 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 299