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  • /*
     * 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)
    {
    	if (n->prev != p || p->next != n) {
    		printk("top: %p, n: %p, p: %p\n", t, t->next, t->prev);
    		printk("prev: %p, n: %p, p: %p\n", p, p->next, p->prev);
    		printk("next: %p, n: %p, p: %p\n", n, n->next, n->prev);
    		WARN_ON(1);
    	}
    }
    
    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->lock);
    	if (head->lock)
    		WARN_ON_SMP(!spin_is_locked(head->lock));
    	plist_check_list(&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 *iter;
    
    	plist_check_head(head);
    	WARN_ON(!plist_node_empty(node));
    
    	list_for_each_entry(iter, &head->prio_list, plist.prio_list) {
    		if (node->prio < iter->prio)
    			goto lt_prio;
    		else if (node->prio == iter->prio) {
    			iter = list_entry(iter->plist.prio_list.next,
    					struct plist_node, plist.prio_list);
    			goto eq_prio;
    		}
    	}
    
    lt_prio:
    	list_add_tail(&node->plist.prio_list, &iter->plist.prio_list);
    eq_prio:
    	list_add_tail(&node->plist.node_list, &iter->plist.node_list);
    
    	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->plist.prio_list)) {
    		struct plist_node *next = plist_first(&node->plist);
    
    		list_move_tail(&next->plist.prio_list, &node->plist.prio_list);
    		list_del_init(&node->plist.prio_list);
    	}
    
    	list_del_init(&node->plist.node_list);
    
    	plist_check_head(head);
    }