1 /*
2 * Descending-priority-sorted double-linked list
3 *
4 * (C) 2002-2003 Intel Corp
5 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
6 *
7 * 2001-2005 (c) MontaVista Software, Inc.
8 * Daniel Walker <dwalker@mvista.com>
9 *
10 * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
11 *
12 * Simplifications of the original code by
13 * Oleg Nesterov <oleg@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 * 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
plist_head_init(struct plist_head * head)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 */
plist_node_init(struct plist_node * node,int prio)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 */
plist_head_empty(const struct plist_head * head)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 */
plist_node_empty(const struct plist_node * node)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 */
plist_first(const struct plist_head * head)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 */
plist_last(const struct plist_head * head)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