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 82 struct plist_head { 83 struct list_head node_list; 84 }; 85 86 struct 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 */ 124 static inline void 125 plist_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 */ 135 static 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 } 141 142 extern void plist_add(struct plist_node *node, struct plist_head *head); 143 extern void plist_del(struct plist_node *node, struct plist_head *head); 144 145 extern 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 */ 213 static 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 */ 222 static 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 */ 283 static 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 */ 295 static 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