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_NODE_INIT - static struct plist_node initializer 102 * @node: struct plist_node variable name 103 * @__prio: initial node priority 104 */ 105 #define PLIST_NODE_INIT(node, __prio) \ 106 { \ 107 .prio = (__prio), \ 108 .prio_list = LIST_HEAD_INIT((node).prio_list), \ 109 .node_list = LIST_HEAD_INIT((node).node_list), \ 110 } 111 112 /** 113 * plist_head_init - dynamic struct plist_head initializer 114 * @head: &struct plist_head pointer 115 */ 116 static inline void 117 plist_head_init(struct plist_head *head) 118 { 119 INIT_LIST_HEAD(&head->node_list); 120 } 121 122 /** 123 * plist_node_init - Dynamic struct plist_node initializer 124 * @node: &struct plist_node pointer 125 * @prio: initial node priority 126 */ 127 static inline void plist_node_init(struct plist_node *node, int prio) 128 { 129 node->prio = prio; 130 INIT_LIST_HEAD(&node->prio_list); 131 INIT_LIST_HEAD(&node->node_list); 132 } 133 134 extern void plist_add(struct plist_node *node, struct plist_head *head); 135 extern void plist_del(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_safe - iterate safely over a plist of given type 147 * @pos: the type * to use as a loop counter 148 * @n: another type * to use as temporary storage 149 * @head: the head for your list 150 * 151 * Iterate over a plist of given type, safe against removal of list entry. 152 */ 153 #define plist_for_each_safe(pos, n, head) \ 154 list_for_each_entry_safe(pos, n, &(head)->node_list, node_list) 155 156 /** 157 * plist_for_each_entry - iterate over list of given type 158 * @pos: the type * to use as a loop counter 159 * @head: the head for your list 160 * @mem: the name of the list_struct within the struct 161 */ 162 #define plist_for_each_entry(pos, head, mem) \ 163 list_for_each_entry(pos, &(head)->node_list, mem.node_list) 164 165 /** 166 * plist_for_each_entry_safe - iterate safely over list 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 * @m: the name of the list_struct within the struct 171 * 172 * Iterate over list of given type, safe against removal of list entry. 173 */ 174 #define plist_for_each_entry_safe(pos, n, head, m) \ 175 list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list) 176 177 /** 178 * plist_head_empty - return !0 if a plist_head is empty 179 * @head: &struct plist_head pointer 180 */ 181 static inline int plist_head_empty(const struct plist_head *head) 182 { 183 return list_empty(&head->node_list); 184 } 185 186 /** 187 * plist_node_empty - return !0 if plist_node is not on a list 188 * @node: &struct plist_node pointer 189 */ 190 static inline int plist_node_empty(const struct plist_node *node) 191 { 192 return list_empty(&node->node_list); 193 } 194 195 /* All functions below assume the plist_head is not empty. */ 196 197 /** 198 * plist_first_entry - get the struct for the first entry 199 * @head: the &struct plist_head pointer 200 * @type: the type of the struct this is embedded in 201 * @member: the name of the list_struct within the struct 202 */ 203 #ifdef CONFIG_DEBUG_PI_LIST 204 # define plist_first_entry(head, type, member) \ 205 ({ \ 206 WARN_ON(plist_head_empty(head)); \ 207 container_of(plist_first(head), type, member); \ 208 }) 209 #else 210 # define plist_first_entry(head, type, member) \ 211 container_of(plist_first(head), type, member) 212 #endif 213 214 /** 215 * plist_last_entry - get the struct for the last entry 216 * @head: the &struct plist_head pointer 217 * @type: the type of the struct this is embedded in 218 * @member: the name of the list_struct within the struct 219 */ 220 #ifdef CONFIG_DEBUG_PI_LIST 221 # define plist_last_entry(head, type, member) \ 222 ({ \ 223 WARN_ON(plist_head_empty(head)); \ 224 container_of(plist_last(head), type, member); \ 225 }) 226 #else 227 # define plist_last_entry(head, type, member) \ 228 container_of(plist_last(head), type, member) 229 #endif 230 231 /** 232 * plist_first - return the first node (and thus, highest priority) 233 * @head: the &struct plist_head pointer 234 * 235 * Assumes the plist is _not_ empty. 236 */ 237 static inline struct plist_node *plist_first(const struct plist_head *head) 238 { 239 return list_entry(head->node_list.next, 240 struct plist_node, node_list); 241 } 242 243 /** 244 * plist_last - return the last node (and thus, lowest priority) 245 * @head: the &struct plist_head pointer 246 * 247 * Assumes the plist is _not_ empty. 248 */ 249 static inline struct plist_node *plist_last(const struct plist_head *head) 250 { 251 return list_entry(head->node_list.prev, 252 struct plist_node, node_list); 253 } 254 255 #endif 256