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 * |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
80struct 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
88struct 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 */
128static inline void
129plist_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 */
144static 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
150extern void plist_add(struct plist_node *node, struct plist_head *head);
151extern 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 */
200static 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 */
210static 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 */
242static 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