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 plist_head_init(struct plist_head * head)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 */ plist_node_init(struct plist_node * node,int prio)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 */ plist_head_empty(const struct plist_head * head)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 */ plist_node_empty(const struct plist_node * node)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 */ plist_first(const struct plist_head * head)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 */ plist_last(const struct plist_head * head)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 292