Root/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
31static 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
43static 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
55static 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    plist_check_list(&head->prio_list);
63    plist_check_list(&head->node_list);
64}
65
66#else
67# define plist_check_head(h) do { } while (0)
68#endif
69
70/**
71 * plist_add - add @node to @head
72 *
73 * @node: &struct plist_node pointer
74 * @head: &struct plist_head pointer
75 */
76void plist_add(struct plist_node *node, struct plist_head *head)
77{
78    struct plist_node *iter;
79
80    plist_check_head(head);
81    WARN_ON(!plist_node_empty(node));
82
83    list_for_each_entry(iter, &head->prio_list, plist.prio_list) {
84        if (node->prio < iter->prio)
85            goto lt_prio;
86        else if (node->prio == iter->prio) {
87            iter = list_entry(iter->plist.prio_list.next,
88                    struct plist_node, plist.prio_list);
89            goto eq_prio;
90        }
91    }
92
93lt_prio:
94    list_add_tail(&node->plist.prio_list, &iter->plist.prio_list);
95eq_prio:
96    list_add_tail(&node->plist.node_list, &iter->plist.node_list);
97
98    plist_check_head(head);
99}
100
101/**
102 * plist_del - Remove a @node from plist.
103 *
104 * @node: &struct plist_node pointer - entry to be removed
105 * @head: &struct plist_head pointer - list head
106 */
107void plist_del(struct plist_node *node, struct plist_head *head)
108{
109    plist_check_head(head);
110
111    if (!list_empty(&node->plist.prio_list)) {
112        struct plist_node *next = plist_first(&node->plist);
113
114        list_move_tail(&next->plist.prio_list, &node->plist.prio_list);
115        list_del_init(&node->plist.prio_list);
116    }
117
118    list_del_init(&node->plist.node_list);
119
120    plist_check_head(head);
121}
122

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