lib/plist.c

/*
 * lib/plist.c
 *
 * Descending-priority-sorted double-linked list
 *
 * (C) 2002-2003 Intel Corp
 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
 *
 * 2001-2005 (c) MontaVista Software, Inc.
 * Daniel Walker <dwalker@mvista.com>
 *
 * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
 *
 * Simplifications of the original code by
 * Oleg Nesterov <oleg@tv-sign.ru>
 *
 * Licensed under the FSF's GNU Public License v2 or later.
 *
 * Based on simple lists (include/linux/list.h).
 *
 * This file contains the add / del functions which are considered to
 * be too large to inline. See include/linux/plist.h for further
 * information.
 */

#include <linux/plist.h>
#include <linux/spinlock.h>

#ifdef CONFIG_DEBUG_PI_LIST

static void plist_check_prev_next(struct list_head *t, struct list_head *p,
				  struct list_head *n)
{
	WARN(n->prev != p || p->next != n,
			"top: %p, n: %p, p: %p\n"
			"prev: %p, n: %p, p: %p\n"
			"next: %p, n: %p, p: %p\n",
			 t, t->next, t->prev,
			p, p->next, p->prev,
			n, n->next, n->prev);
}

static void plist_check_list(struct list_head *top)
{
	struct list_head *prev = top, *next = top->next;

	plist_check_prev_next(top, prev, next);
	while (next != top) {
		prev = next;
		next = prev->next;
		plist_check_prev_next(top, prev, next);
	}
}

static void plist_check_head(struct plist_head *head)
{
	WARN_ON(!head->rawlock && !head->spinlock);
	if (head->rawlock)
		WARN_ON_SMP(!raw_spin_is_locked(head->rawlock));
	if (head->spinlock)
		WARN_ON_SMP(!spin_is_locked(head->spinlock));
	if (!plist_head_empty(head))
		plist_check_list(&plist_first(head)->prio_list);
	plist_check_list(&head->node_list);
}

#else
# define plist_check_head(h)	do { } while (0)
#endif

/**
 * plist_add - add @node to @head
 *
 * @node:	&struct plist_node pointer
 * @head:	&struct plist_head pointer
 */
void plist_add(struct plist_node *node, struct plist_head *head)
{
	struct plist_node *first, *iter, *prev = NULL;
	struct list_head *node_next = &head->node_list;

	plist_check_head(head);
	WARN_ON(!plist_node_empty(node));
	WARN_ON(!list_empty(&node->prio_list));

	if (plist_head_empty(head))
		goto ins_node;

	first = iter = plist_first(head);

	do {
		if (node->prio < iter->prio) {
			node_next = &iter->node_list;
			break;
		}

		prev = iter;
		iter = list_entry(iter->prio_list.next,
				struct plist_node, prio_list);
	} while (iter != first);

	if (!prev || prev->prio != node->prio)
		list_add_tail(&node->prio_list, &iter->prio_list);
ins_node:
	list_add_tail(&node->node_list, node_next);

	plist_check_head(head);
}

/**
 * plist_del - Remove a @node from plist.
 *
 * @node:	&struct plist_node pointer - entry to be removed
 * @head:	&struct plist_head pointer - list head
 */
void plist_del(struct plist_node *node, struct plist_head *head)
{
	plist_check_head(head);

	if (!list_empty(&node->prio_list)) {
		if (node->node_list.next != &head->node_list) {
			struct plist_node *next;

			next = list_entry(node->node_list.next,
					struct plist_node, node_list);

			/* add the next plist_node into prio_list */
			if (list_empty(&next->prio_list))
				list_add(&next->prio_list, &node->prio_list);
		}
		list_del_init(&node->prio_list);
	}

	list_del_init(&node->node_list);

	plist_check_head(head);
}