1 /* 2 * Descending-priority-sorted double-linked list 3 * 4 * (C) 2002-2003 Intel Corp 5 * Inaky Perez-Gonzalez <inaky.perez-gonzalez (at) intel.com>. 6 * 7 * 2001-2005 (c) MontaVista Software, Inc. 8 * Daniel Walker <dwalker (at) mvista.com> 9 * 10 * (C) 2005 Thomas Gleixner <tglx (at) linutronix.de> 11 * 12 * Simplifications of the original code by 13 * Oleg Nesterov <oleg (at) tv-sign.ru> 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 * |HEAD | 35 * | | 36 * |prio_list.prev|<------------------------------------| 37 * |prio_list.next|<->|pl|<->|pl|<--------------->|pl|<-| 38 * |10 | |10| |21| |21| |21| |40| (prio) 39 * | | | | | | | | | | | | 40 * | | | | | | | | | | | | 41 * |node_list.next|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-| 42 * |node_list.prev|<------------------------------------| 43 * 44 * The nodes on the prio_list list are sorted by priority to simplify 45 * the insertion of new nodes. There are no nodes with duplicate 46 * priorites on the list. 47 * 48 * The nodes on the node_list is ordered by priority and can contain 49 * entries which have the same priority. Those entries are ordered 50 * FIFO 51 * 52 * Addition means: look for the prio_list node in the prio_list 53 * for the priority of the node and insert it before the node_list 54 * entry of the next prio_list node. If it is the first node of 55 * that priority, add it to the prio_list in the right position and 56 * insert it into the serialized node_list list 57 * 58 * Removal means remove it from the node_list and remove it from 59 * the prio_list if the node_list list_head is non empty. In case 60 * of removal from the prio_list it must be checked whether other 61 * entries of the same priority are on the list or not. If there 62 * is another entry of the same priority then this entry has to 63 * replace the removed entry on the prio_list. If the entry which 64 * is removed is the only entry of this priority then a simple 65 * remove from both list is sufficient. 66 * 67 * INT_MIN is the highest priority, 0 is the medium highest, INT_MAX 68 * is lowest priority. 69 * 70 * No locking is done, up to the caller. 71 * 72 */ 73 #ifndef _LINUX_PLIST_H_ 74 #define _LINUX_PLIST_H_ 75 76 #include <linux/kernel.h> 77 #include <linux/list.h> 78 #include <linux/spinlock_types.h> 79 80 struct plist_head { 81 struct list_head prio_list; 82 struct list_head node_list; 83 #ifdef CONFIG_DEBUG_PI_LIST 84 spinlock_t *lock; 85 #endif 86 }; 87 88 struct plist_node { 89 int prio; 90 struct plist_head plist; 91 }; 92 93 #ifdef CONFIG_DEBUG_PI_LIST 94 # define PLIST_HEAD_LOCK_INIT(_lock) .lock = _lock 95 #else 96 # define PLIST_HEAD_LOCK_INIT(_lock) 97 #endif 98 99 /** 100 * #PLIST_HEAD_INIT - static struct plist_head initializer 101 * 102 * @head: struct plist_head variable name 103 */ 104 #define PLIST_HEAD_INIT(head, _lock) \ 105 { \ 106 .prio_list = LIST_HEAD_INIT((head).prio_list), \ 107 .node_list = LIST_HEAD_INIT((head).node_list), \ 108 PLIST_HEAD_LOCK_INIT(&(_lock)) \ 109 } 110 111 /** 112 * #PLIST_NODE_INIT - static struct plist_node initializer 113 * 114 * @node: struct plist_node variable name 115 * @__prio: initial node priority 116 */ 117 #define PLIST_NODE_INIT(node, __prio) \ 118 { \ 119 .prio = (__prio), \ 120 .plist = PLIST_HEAD_INIT((node).plist, NULL), \ 121 } 122 123 /** 124 * plist_head_init - dynamic struct plist_head initializer 125 * 126 * @head: &struct plist_head pointer 127 */ 128 static inline void 129 plist_head_init(struct plist_head *head, spinlock_t *lock) 130 { 131 INIT_LIST_HEAD(&head->prio_list); 132 INIT_LIST_HEAD(&head->node_list); 133 #ifdef CONFIG_DEBUG_PI_LIST 134 head->lock = lock; 135 #endif 136 } 137 138 /** 139 * plist_node_init - Dynamic struct plist_node initializer 140 * 141 * @node: &struct plist_node pointer 142 * @prio: initial node priority 143 */ 144 static inline void plist_node_init(struct plist_node *node, int prio) 145 { 146 node->prio = prio; 147 plist_head_init(&node->plist, NULL); 148 } 149 150 extern void plist_add(struct plist_node *node, struct plist_head *head); 151 extern void plist_del(struct plist_node *node, struct plist_head *head); 152 153 /** 154 * plist_for_each - iterate over the plist 155 * 156 * @pos1: the type * to use as a loop counter. 157 * @head: the head for your list. 158 */ 159 #define plist_for_each(pos, head) \ 160 list_for_each_entry(pos, &(head)->node_list, plist.node_list) 161 162 /** 163 * plist_for_each_entry_safe - iterate over a plist of given type safe 164 * against removal of list entry 165 * 166 * @pos1: the type * to use as a loop counter. 167 * @n1: another type * to use as temporary storage 168 * @head: the head for your list. 169 */ 170 #define plist_for_each_safe(pos, n, head) \ 171 list_for_each_entry_safe(pos, n, &(head)->node_list, plist.node_list) 172 173 /** 174 * plist_for_each_entry - iterate over list of given type 175 * 176 * @pos: the type * to use as a loop counter. 177 * @head: the head for your list. 178 * @member: the name of the list_struct within the struct. 179 */ 180 #define plist_for_each_entry(pos, head, mem) \ 181 list_for_each_entry(pos, &(head)->node_list, mem.plist.node_list) 182 183 /** 184 * plist_for_each_entry_safe - iterate over list of given type safe against 185 * removal of list entry 186 * 187 * @pos: the type * to use as a loop counter. 188 * @n: another type * to use as temporary storage 189 * @head: the head for your list. 190 * @m: the name of the list_struct within the struct. 191 */ 192 #define plist_for_each_entry_safe(pos, n, head, m) \ 193 list_for_each_entry_safe(pos, n, &(head)->node_list, m.plist.node_list) 194 195 /** 196 * plist_head_empty - return !0 if a plist_head is empty 197 * 198 * @head: &struct plist_head pointer 199 */ 200 static inline int plist_head_empty(const struct plist_head *head) 201 { 202 return list_empty(&head->node_list); 203 } 204 205 /** 206 * plist_node_empty - return !0 if plist_node is not on a list 207 * 208 * @node: &struct plist_node pointer 209 */ 210 static inline int plist_node_empty(const struct plist_node *node) 211 { 212 return plist_head_empty(&node->plist); 213 } 214 215 /* All functions below assume the plist_head is not empty. */ 216 217 /** 218 * plist_first_entry - get the struct for the first entry 219 * 220 * @ptr: the &struct plist_head pointer. 221 * @type: the type of the struct this is embedded in. 222 * @member: the name of the list_struct within the struct. 223 */ 224 #ifdef CONFIG_DEBUG_PI_LIST 225 # define plist_first_entry(head, type, member) \ 226 ({ \ 227 WARN_ON(plist_head_empty(head)); \ 228 container_of(plist_first(head), type, member); \ 229 }) 230 #else 231 # define plist_first_entry(head, type, member) \ 232 container_of(plist_first(head), type, member) 233 #endif 234 235 /** 236 * plist_first - return the first node (and thus, highest priority) 237 * 238 * @head: the &struct plist_head pointer 239 * 240 * Assumes the plist is _not_ empty. 241 */ 242 static inline struct plist_node* plist_first(const struct plist_head *head) 243 { 244 return list_entry(head->node_list.next, 245 struct plist_node, plist.node_list); 246 } 247 248 #endif 249
