1  /* SPDX-License-Identifier: GPL-2.0-or-later */
2  /*
3   * Descending-priority-sorted double-linked list
4   *
5   * (C) 2002-2003 Intel Corp
6   * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
7   *
8   * 2001-2005 (c) MontaVista Software, Inc.
9   * Daniel Walker <dwalker@mvista.com>
10   *
11   * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
12   *
13   * Simplifications of the original code by
14   * Oleg Nesterov <oleg@tv-sign.ru>
15   *
16   * Based on simple lists (include/linux/list.h).
17   *
18   * This is a priority-sorted list of nodes; each node has a
19   * priority from INT_MIN (highest) to INT_MAX (lowest).
20   *
21   * Addition is O(K), removal is O(1), change of priority of a node is
22   * O(K) and K is the number of RT priority levels used in the system.
23   * (1 <= K <= 99)
24   *
25   * This list is really a list of lists:
26   *
27   *  - The tier 1 list is the prio_list, different priority nodes.
28   *
29   *  - The tier 2 list is the node_list, serialized nodes.
30   *
31   * Simple ASCII art explanation:
32   *
33   * pl:prio_list (only for plist_node)
34   * nl:node_list
35   *   HEAD|             NODE(S)
36   *       |
37   *       ||------------------------------------|
38   *       ||->|pl|<->|pl|<--------------->|pl|<-|
39   *       |   |10|   |21|   |21|   |21|   |40|   (prio)
40   *       |   |  |   |  |   |  |   |  |   |  |
41   *       |   |  |   |  |   |  |   |  |   |  |
42   * |->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
43   * |-------------------------------------------|
44   *
45   * The nodes on the prio_list list are sorted by priority to simplify
46   * the insertion of new nodes. There are no nodes with duplicate
47   * priorites on the list.
48   *
49   * The nodes on the node_list are ordered by priority and can contain
50   * entries which have the same priority. Those entries are ordered
51   * FIFO
52   *
53   * Addition means: look for the prio_list node in the prio_list
54   * for the priority of the node and insert it before the node_list
55   * entry of the next prio_list node. If it is the first node of
56   * that priority, add it to the prio_list in the right position and
57   * insert it into the serialized node_list list
58   *
59   * Removal means remove it from the node_list and remove it from
60   * the prio_list if the node_list list_head is non empty. In case
61   * of removal from the prio_list it must be checked whether other
62   * entries of the same priority are on the list or not. If there
63   * is another entry of the same priority then this entry has to
64   * replace the removed entry on the prio_list. If the entry which
65   * is removed is the only entry of this priority then a simple
66   * remove from both list is sufficient.
67   *
68   * INT_MIN is the highest priority, 0 is the medium highest, INT_MAX
69   * is lowest priority.
70   *
71   * No locking is done, up to the caller.
72   */
73  #ifndef _LINUX_PLIST_H_
74  #define _LINUX_PLIST_H_
75  
76  #include <linux/container_of.h>
77  #include <linux/list.h>
78  #include <linux/plist_types.h>
79  
80  #include <asm/bug.h>
81  
82  /**
83   * PLIST_HEAD_INIT - static struct plist_head initializer
84   * @head:	struct plist_head variable name
85   */
86  #define PLIST_HEAD_INIT(head)				\
87  {							\
88  	.node_list = LIST_HEAD_INIT((head).node_list)	\
89  }
90  
91  /**
92   * PLIST_HEAD - declare and init plist_head
93   * @head:	name for struct plist_head variable
94   */
95  #define PLIST_HEAD(head) \
96  	struct plist_head head = PLIST_HEAD_INIT(head)
97  
98  /**
99   * PLIST_NODE_INIT - static struct plist_node initializer
100   * @node:	struct plist_node variable name
101   * @__prio:	initial node priority
102   */
103  #define PLIST_NODE_INIT(node, __prio)			\
104  {							\
105  	.prio  = (__prio),				\
106  	.prio_list = LIST_HEAD_INIT((node).prio_list),	\
107  	.node_list = LIST_HEAD_INIT((node).node_list),	\
108  }
109  
110  /**
111   * plist_head_init - dynamic struct plist_head initializer
112   * @head:	&struct plist_head pointer
113   */
114  static inline void
plist_head_init(struct plist_head * head)115  plist_head_init(struct plist_head *head)
116  {
117  	INIT_LIST_HEAD(&head->node_list);
118  }
119  
120  /**
121   * plist_node_init - Dynamic struct plist_node initializer
122   * @node:	&struct plist_node pointer
123   * @prio:	initial node priority
124   */
plist_node_init(struct plist_node * node,int prio)125  static inline void plist_node_init(struct plist_node *node, int prio)
126  {
127  	node->prio = prio;
128  	INIT_LIST_HEAD(&node->prio_list);
129  	INIT_LIST_HEAD(&node->node_list);
130  }
131  
132  extern void plist_add(struct plist_node *node, struct plist_head *head);
133  extern void plist_del(struct plist_node *node, struct plist_head *head);
134  
135  extern void plist_requeue(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_continue - continue iteration over the plist
147   * @pos:	the type * to use as a loop cursor
148   * @head:	the head for your list
149   *
150   * Continue to iterate over plist, continuing after the current position.
151   */
152  #define plist_for_each_continue(pos, head)	\
153  	 list_for_each_entry_continue(pos, &(head)->node_list, node_list)
154  
155  /**
156   * plist_for_each_safe - iterate safely over a plist of given type
157   * @pos:	the type * to use as a loop counter
158   * @n:	another type * to use as temporary storage
159   * @head:	the head for your list
160   *
161   * Iterate over a plist of given type, safe against removal of list entry.
162   */
163  #define plist_for_each_safe(pos, n, head)	\
164  	 list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)
165  
166  /**
167   * plist_for_each_entry	- iterate over list of given type
168   * @pos:	the type * to use as a loop counter
169   * @head:	the head for your list
170   * @mem:	the name of the list_head within the struct
171   */
172  #define plist_for_each_entry(pos, head, mem)	\
173  	 list_for_each_entry(pos, &(head)->node_list, mem.node_list)
174  
175  /**
176   * plist_for_each_entry_continue - continue iteration over list of given type
177   * @pos:	the type * to use as a loop cursor
178   * @head:	the head for your list
179   * @m:		the name of the list_head within the struct
180   *
181   * Continue to iterate over list of given type, continuing after
182   * the current position.
183   */
184  #define plist_for_each_entry_continue(pos, head, m)	\
185  	list_for_each_entry_continue(pos, &(head)->node_list, m.node_list)
186  
187  /**
188   * plist_for_each_entry_safe - iterate safely over list of given type
189   * @pos:	the type * to use as a loop counter
190   * @n:		another type * to use as temporary storage
191   * @head:	the head for your list
192   * @m:		the name of the list_head within the struct
193   *
194   * Iterate over list of given type, safe against removal of list entry.
195   */
196  #define plist_for_each_entry_safe(pos, n, head, m)	\
197  	list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)
198  
199  /**
200   * plist_head_empty - return !0 if a plist_head is empty
201   * @head:	&struct plist_head pointer
202   */
plist_head_empty(const struct plist_head * head)203  static inline int plist_head_empty(const struct plist_head *head)
204  {
205  	return list_empty(&head->node_list);
206  }
207  
208  /**
209   * plist_node_empty - return !0 if plist_node is not on a list
210   * @node:	&struct plist_node pointer
211   */
plist_node_empty(const struct plist_node * node)212  static inline int plist_node_empty(const struct plist_node *node)
213  {
214  	return list_empty(&node->node_list);
215  }
216  
217  /* All functions below assume the plist_head is not empty. */
218  
219  /**
220   * plist_first_entry - get the struct for the first entry
221   * @head:	the &struct plist_head pointer
222   * @type:	the type of the struct this is embedded in
223   * @member:	the name of the list_head within the struct
224   */
225  #ifdef CONFIG_DEBUG_PLIST
226  # define plist_first_entry(head, type, member)	\
227  ({ \
228  	WARN_ON(plist_head_empty(head)); \
229  	container_of(plist_first(head), type, member); \
230  })
231  #else
232  # define plist_first_entry(head, type, member)	\
233  	container_of(plist_first(head), type, member)
234  #endif
235  
236  /**
237   * plist_last_entry - get the struct for the last entry
238   * @head:	the &struct plist_head pointer
239   * @type:	the type of the struct this is embedded in
240   * @member:	the name of the list_head within the struct
241   */
242  #ifdef CONFIG_DEBUG_PLIST
243  # define plist_last_entry(head, type, member)	\
244  ({ \
245  	WARN_ON(plist_head_empty(head)); \
246  	container_of(plist_last(head), type, member); \
247  })
248  #else
249  # define plist_last_entry(head, type, member)	\
250  	container_of(plist_last(head), type, member)
251  #endif
252  
253  /**
254   * plist_next - get the next entry in list
255   * @pos:	the type * to cursor
256   */
257  #define plist_next(pos) \
258  	list_next_entry(pos, node_list)
259  
260  /**
261   * plist_prev - get the prev entry in list
262   * @pos:	the type * to cursor
263   */
264  #define plist_prev(pos) \
265  	list_prev_entry(pos, node_list)
266  
267  /**
268   * plist_first - return the first node (and thus, highest priority)
269   * @head:	the &struct plist_head pointer
270   *
271   * Assumes the plist is _not_ empty.
272   */
plist_first(const struct plist_head * head)273  static inline struct plist_node *plist_first(const struct plist_head *head)
274  {
275  	return list_entry(head->node_list.next,
276  			  struct plist_node, node_list);
277  }
278  
279  /**
280   * plist_last - return the last node (and thus, lowest priority)
281   * @head:	the &struct plist_head pointer
282   *
283   * Assumes the plist is _not_ empty.
284   */
plist_last(const struct plist_head * head)285  static inline struct plist_node *plist_last(const struct plist_head *head)
286  {
287  	return list_entry(head->node_list.prev,
288  			  struct plist_node, node_list);
289  }
290  
291  #endif
292