plist: Shrink struct plist_head
[linux-3.10.git] / lib / plist.c
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->rawlock && !head->spinlock);
58         if (head->rawlock)
59                 WARN_ON_SMP(!raw_spin_is_locked(head->rawlock));
60         if (head->spinlock)
61                 WARN_ON_SMP(!spin_is_locked(head->spinlock));
62         if (!plist_head_empty(head))
63                 plist_check_list(&plist_first(head)->prio_list);
64         plist_check_list(&head->node_list);
65 }
66
67 #else
68 # define plist_check_head(h)    do { } while (0)
69 #endif
70
71 /**
72  * plist_add - add @node to @head
73  *
74  * @node:       &struct plist_node pointer
75  * @head:       &struct plist_head pointer
76  */
77 void plist_add(struct plist_node *node, struct plist_head *head)
78 {
79         struct plist_node *first, *iter, *prev = NULL;
80         struct list_head *node_next = &head->node_list;
81
82         plist_check_head(head);
83         WARN_ON(!plist_node_empty(node));
84         WARN_ON(!list_empty(&node->prio_list));
85
86         if (plist_head_empty(head))
87                 goto ins_node;
88
89         first = iter = plist_first(head);
90
91         do {
92                 if (node->prio < iter->prio) {
93                         node_next = &iter->node_list;
94                         break;
95                 }
96
97                 prev = iter;
98                 iter = list_entry(iter->prio_list.next,
99                                 struct plist_node, prio_list);
100         } while (iter != first);
101
102         if (!prev || prev->prio != node->prio)
103                 list_add_tail(&node->prio_list, &iter->prio_list);
104 ins_node:
105         list_add_tail(&node->node_list, node_next);
106
107         plist_check_head(head);
108 }
109
110 /**
111  * plist_del - Remove a @node from plist.
112  *
113  * @node:       &struct plist_node pointer - entry to be removed
114  * @head:       &struct plist_head pointer - list head
115  */
116 void plist_del(struct plist_node *node, struct plist_head *head)
117 {
118         plist_check_head(head);
119
120         if (!list_empty(&node->prio_list)) {
121                 if (node->node_list.next != &head->node_list) {
122                         struct plist_node *next;
123
124                         next = list_entry(node->node_list.next,
125                                         struct plist_node, node_list);
126
127                         /* add the next plist_node into prio_list */
128                         if (list_empty(&next->prio_list))
129                                 list_add(&next->prio_list, &node->prio_list);
130                 }
131                 list_del_init(&node->prio_list);
132         }
133
134         list_del_init(&node->node_list);
135
136         plist_check_head(head);
137 }