1 /* 2 * Descending-priority-sorted double-linked list 3 * 4 * (C) 2002-2003 Intel Corp 5 * Inaky Perez-Gonzalez <[email protected]>. 6 * 7 * 2001-2005 (c) MontaVista Software, Inc. 8 * Daniel Walker <[email protected]> 9 * 10 * (C) 2005 Thomas Gleixner <[email protected]> 11 * 12 * Simplifications of the original code by 13 * Oleg Nesterov <[email protected]> 14 * 15 * Licensed under the FSF's GNU Public License v2 or later. 16 * 17 * Based on simple lists (include/linux/list.h). 18 * 19 * This is a priority-sorted list of nodes; each node has a 20 * priority from INT_MIN (highest) to INT_MAX (lowest). 21 * 22 * Addition is O(K), removal is O(1), change of priority of a node is 23 * O(K) and K is the number of RT priority levels used in the system. 24 * (1 <= K <= 99) 25 * 26 * This list is really a list of lists: 27 * 28 * - The tier 1 list is the prio_list, different priority nodes. 29 * 30 * - The tier 2 list is the node_list, serialized nodes. 31 * 32 * Simple ASCII art explanation: 33 * 34 * pl:prio_list (only for plist_node) 35 * nl:node_list 36 * HEAD| NODE(S) 37 * | 38 * ||------------------------------------| 39 * ||->|pl|<->|pl|<--------------->|pl|<-| 40 * | |10| |21| |21| |21| |40| (prio) 41 * | | | | | | | | | | | 42 * | | | | | | | | | | | 43 * |->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-| 44 * |-------------------------------------------| 45 * 46 * The nodes on the prio_list list are sorted by priority to simplify 47 * the insertion of new nodes. There are no nodes with duplicate 48 * priorites on the list. 49 * 50 * The nodes on the node_list are ordered by priority and can contain 51 * entries which have the same priority. Those entries are ordered 52 * FIFO 53 * 54 * Addition means: look for the prio_list node in the prio_list 55 * for the priority of the node and insert it before the node_list 56 * entry of the next prio_list node. If it is the first node of 57 * that priority, add it to the prio_list in the right position and 58 * insert it into the serialized node_list list 59 * 60 * Removal means remove it from the node_list and remove it from 61 * the prio_list if the node_list list_head is non empty. In case 62 * of removal from the prio_list it must be checked whether other 63 * entries of the same priority are on the list or not. If there 64 * is another entry of the same priority then this entry has to 65 * replace the removed entry on the prio_list. If the entry which 66 * is removed is the only entry of this priority then a simple 67 * remove from both list is sufficient. 68 * 69 * INT_MIN is the highest priority, 0 is the medium highest, INT_MAX 70 * is lowest priority. 71 * 72 * No locking is done, up to the caller. 73 * 74 */ 75 #ifndef _LINUX_PLIST_H_ 76 #define _LINUX_PLIST_H_ 77 78 #include <linux/kernel.h> 79 #include <linux/list.h> 80 81 struct plist_head { 82 struct list_head node_list; 83 }; 84 85 struct plist_node { 86 int prio; 87 struct list_head prio_list; 88 struct list_head node_list; 89 }; 90 91 /** 92 * PLIST_HEAD_INIT - static struct plist_head initializer 93 * @head: struct plist_head variable name 94 */ 95 #define PLIST_HEAD_INIT(head) \ 96 { \ 97 .node_list = LIST_HEAD_INIT((head).node_list) \ 98 } 99 100 /** 101 * PLIST_HEAD - declare and init plist_head 102 * @head: name for struct plist_head variable 103 */ 104 #define PLIST_HEAD(head) \ 105 struct plist_head head = PLIST_HEAD_INIT(head) 106 107 /** 108 * PLIST_NODE_INIT - static struct plist_node initializer 109 * @node: struct plist_node variable name 110 * @__prio: initial node priority 111 */ 112 #define PLIST_NODE_INIT(node, __prio) \ 113 { \ 114 .prio = (__prio), \ 115 .prio_list = LIST_HEAD_INIT((node).prio_list), \ 116 .node_list = LIST_HEAD_INIT((node).node_list), \ 117 } 118 119 /** 120 * plist_head_init - dynamic struct plist_head initializer 121 * @head: &struct plist_head pointer 122 */ 123 static inline void 124 plist_head_init(struct plist_head *head) 125 { 126 INIT_LIST_HEAD(&head->node_list); 127 } 128 129 /** 130 * plist_node_init - Dynamic struct plist_node initializer 131 * @node: &struct plist_node pointer 132 * @prio: initial node priority 133 */ 134 static inline void plist_node_init(struct plist_node *node, int prio) 135 { 136 node->prio = prio; 137 INIT_LIST_HEAD(&node->prio_list); 138 INIT_LIST_HEAD(&node->node_list); 139 } 140 141 extern void plist_add(struct plist_node *node, struct plist_head *head); 142 extern void plist_del(struct plist_node *node, struct plist_head *head); 143 144 extern void plist_requeue(struct plist_node *node, struct plist_head *head); 145 146 /** 147 * plist_for_each - iterate over the plist 148 * @pos: the type * to use as a loop counter 149 * @head: the head for your list 150 */ 151 #define plist_for_each(pos, head) \ 152 list_for_each_entry(pos, &(head)->node_list, node_list) 153 154 /** 155 * plist_for_each_continue - continue iteration over the plist 156 * @pos: the type * to use as a loop cursor 157 * @head: the head for your list 158 * 159 * Continue to iterate over plist, continuing after the current position. 160 */ 161 #define plist_for_each_continue(pos, head) \ 162 list_for_each_entry_continue(pos, &(head)->node_list, node_list) 163 164 /** 165 * plist_for_each_safe - iterate safely over a plist of given type 166 * @pos: the type * to use as a loop counter 167 * @n: another type * to use as temporary storage 168 * @head: the head for your list 169 * 170 * Iterate over a plist of given type, safe against removal of list entry. 171 */ 172 #define plist_for_each_safe(pos, n, head) \ 173 list_for_each_entry_safe(pos, n, &(head)->node_list, node_list) 174 175 /** 176 * plist_for_each_entry - iterate over list of given type 177 * @pos: the type * to use as a loop counter 178 * @head: the head for your list 179 * @mem: the name of the list_head within the struct 180 */ 181 #define plist_for_each_entry(pos, head, mem) \ 182 list_for_each_entry(pos, &(head)->node_list, mem.node_list) 183 184 /** 185 * plist_for_each_entry_continue - continue iteration over list of given type 186 * @pos: the type * to use as a loop cursor 187 * @head: the head for your list 188 * @m: the name of the list_head within the struct 189 * 190 * Continue to iterate over list of given type, continuing after 191 * the current position. 192 */ 193 #define plist_for_each_entry_continue(pos, head, m) \ 194 list_for_each_entry_continue(pos, &(head)->node_list, m.node_list) 195 196 /** 197 * plist_for_each_entry_safe - iterate safely over list of given type 198 * @pos: the type * to use as a loop counter 199 * @n: another type * to use as temporary storage 200 * @head: the head for your list 201 * @m: the name of the list_head within the struct 202 * 203 * Iterate over list of given type, safe against removal of list entry. 204 */ 205 #define plist_for_each_entry_safe(pos, n, head, m) \ 206 list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list) 207 208 /** 209 * plist_head_empty - return !0 if a plist_head is empty 210 * @head: &struct plist_head pointer 211 */ 212 static inline int plist_head_empty(const struct plist_head *head) 213 { 214 return list_empty(&head->node_list); 215 } 216 217 /** 218 * plist_node_empty - return !0 if plist_node is not on a list 219 * @node: &struct plist_node pointer 220 */ 221 static inline int plist_node_empty(const struct plist_node *node) 222 { 223 return list_empty(&node->node_list); 224 } 225 226 /* All functions below assume the plist_head is not empty. */ 227 228 /** 229 * plist_first_entry - get the struct for the first entry 230 * @head: the &struct plist_head pointer 231 * @type: the type of the struct this is embedded in 232 * @member: the name of the list_head within the struct 233 */ 234 #ifdef CONFIG_DEBUG_PI_LIST 235 # define plist_first_entry(head, type, member) \ 236 ({ \ 237 WARN_ON(plist_head_empty(head)); \ 238 container_of(plist_first(head), type, member); \ 239 }) 240 #else 241 # define plist_first_entry(head, type, member) \ 242 container_of(plist_first(head), type, member) 243 #endif 244 245 /** 246 * plist_last_entry - get the struct for the last entry 247 * @head: the &struct plist_head pointer 248 * @type: the type of the struct this is embedded in 249 * @member: the name of the list_head within the struct 250 */ 251 #ifdef CONFIG_DEBUG_PI_LIST 252 # define plist_last_entry(head, type, member) \ 253 ({ \ 254 WARN_ON(plist_head_empty(head)); \ 255 container_of(plist_last(head), type, member); \ 256 }) 257 #else 258 # define plist_last_entry(head, type, member) \ 259 container_of(plist_last(head), type, member) 260 #endif 261 262 /** 263 * plist_next - get the next entry in list 264 * @pos: the type * to cursor 265 */ 266 #define plist_next(pos) \ 267 list_next_entry(pos, node_list) 268 269 /** 270 * plist_prev - get the prev entry in list 271 * @pos: the type * to cursor 272 */ 273 #define plist_prev(pos) \ 274 list_prev_entry(pos, node_list) 275 276 /** 277 * plist_first - return the first node (and thus, highest priority) 278 * @head: the &struct plist_head pointer 279 * 280 * Assumes the plist is _not_ empty. 281 */ 282 static inline struct plist_node *plist_first(const struct plist_head *head) 283 { 284 return list_entry(head->node_list.next, 285 struct plist_node, node_list); 286 } 287 288 /** 289 * plist_last - return the last node (and thus, lowest priority) 290 * @head: the &struct plist_head pointer 291 * 292 * Assumes the plist is _not_ empty. 293 */ 294 static inline struct plist_node *plist_last(const struct plist_head *head) 295 { 296 return list_entry(head->node_list.prev, 297 struct plist_node, node_list); 298 } 299 300 #endif 301