1 /*
2 * lib/plist.c
3 *
4 * Descending-priority-sorted double-linked list
5 *
6 * (C) 2002-2003 Intel Corp
7 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
8 *
9 * 2001-2005 (c) MontaVista Software, Inc.
10 * Daniel Walker <dwalker@mvista.com>
11 *
12 * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
13 *
14 * Simplifications of the original code by
15 * Oleg Nesterov <oleg@tv-sign.ru>
16 *
17 * Licensed under the FSF's GNU Public License v2 or later.
18 *
19 * Based on simple lists (include/linux/list.h).
20 *
21 * This file contains the add / del functions which are considered to
22 * be too large to inline. See include/linux/plist.h for further
23 * information.
24 */
25
26 #include <linux/plist.h>
27 #include <linux/spinlock.h>
28
29 #ifdef CONFIG_DEBUG_PI_LIST
30
31 static void plist_check_prev_next(struct list_head *t, struct list_head *p,
32 struct list_head *n)
33 {
34 WARN(n->prev != p || p->next != n,
35 "top: %p, n: %p, p: %p\n"
36 "prev: %p, n: %p, p: %p\n"
37 "next: %p, n: %p, p: %p\n",
38 t, t->next, t->prev,
39 p, p->next, p->prev,
40 n, n->next, n->prev);
41 }
42
43 static void plist_check_list(struct list_head *top)
44 {
45 struct list_head *prev = top, *next = top->next;
46
47 plist_check_prev_next(top, prev, next);
48 while (next != top) {
49 prev = next;
50 next = prev->next;
51 plist_check_prev_next(top, prev, next);
52 }
53 }
54
55 static void plist_check_head(struct plist_head *head)
56 {
57 WARN_ON(!head->lock);
58 if (head->lock)
59 WARN_ON_SMP(!spin_is_locked(head->lock));
60 plist_check_list(&head->prio_list);
61 plist_check_list(&head->node_list);
62 }
63
64 #else
65 # define plist_check_head(h) do { } while (0)
66 #endif
67
68 /**
69 * plist_add - add @node to @head
70 *
71 * @node: &struct plist_node pointer
72 * @head: &struct plist_head pointer
73 */
74 void plist_add(struct plist_node *node, struct plist_head *head)
75 {
76 struct plist_node *iter;
77
78 plist_check_head(head);
79 WARN_ON(!plist_node_empty(node));
80
81 list_for_each_entry(iter, &head->prio_list, plist.prio_list) {
82 if (node->prio < iter->prio)
83 goto lt_prio;
84 else if (node->prio == iter->prio) {
85 iter = list_entry(iter->plist.prio_list.next,
86 struct plist_node, plist.prio_list);
87 goto eq_prio;
88 }
89 }
90
91 lt_prio:
92 list_add_tail(&node->plist.prio_list, &iter->plist.prio_list);
93 eq_prio:
94 list_add_tail(&node->plist.node_list, &iter->plist.node_list);
95
96 plist_check_head(head);
97 }
98
99 /**
100 * plist_del - Remove a @node from plist.
101 *
102 * @node: &struct plist_node pointer - entry to be removed
103 * @head: &struct plist_head pointer - list head
104 */
105 void plist_del(struct plist_node *node, struct plist_head *head)
106 {
107 plist_check_head(head);
108
109 if (!list_empty(&node->plist.prio_list)) {
110 struct plist_node *next = plist_first(&node->plist);
111
112 list_move_tail(&next->plist.prio_list, &node->plist.prio_list);
113 list_del_init(&node->plist.prio_list);
114 }
115
116 list_del_init(&node->plist.node_list);
117
118 plist_check_head(head);
119 }
120
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