xref: /openbmc/linux/lib/plist.c (revision 9d56dd3b083a3bec56e9da35ce07baca81030b03)
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 	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  */
76 void 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 
93 lt_prio:
94 	list_add_tail(&node->plist.prio_list, &iter->plist.prio_list);
95 eq_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  */
107 void 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