plist.h

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/*
 * Descending-priority-sorted double-linked list
 *
 * (C) 2002-2003 Intel Corp
 * Inaky Perez-Gonzalez <[email protected]>.
 *
 * 2001-2005 (c) MontaVista Software, Inc.
 * Daniel Walker <[email protected]>
 *
 * (C) 2005 Thomas Gleixner <[email protected]>
 *
 * Simplifications of the original code by
 * Oleg Nesterov <[email protected]>
 *
 * Licensed under the FSF's GNU Public License v2 or later.
 *
 * Based on simple lists (include/linux/list.h).
 *
 * This is a priority-sorted list of nodes; each node has a
 * priority from INT_MIN (highest) to INT_MAX (lowest).
 *
 * Addition is O(K), removal is O(1), change of priority of a node is
 * O(K) and K is the number of RT priority levels used in the system.
 * (1 <= K <= 99)
 *
 * This list is really a list of lists:
 *
 *  - The tier 1 list is the prio_list, different priority nodes.
 *
 *  - The tier 2 list is the node_list, serialized nodes.
 *
 * Simple ASCII art explanation:
 *
 * pl:prio_list (only for plist_node)
 * nl:node_list
 *   HEAD|             NODE(S)
 *       |
 *       ||------------------------------------|
 *       ||->|pl|<->|pl|<--------------->|pl|<-|
 *       |   |10|   |21|   |21|   |21|   |40|   (prio)
 *       |   |  |   |  |   |  |   |  |   |  |
 *       |   |  |   |  |   |  |   |  |   |  |
 * |->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
 * |-------------------------------------------|
 *
 * The nodes on the prio_list list are sorted by priority to simplify
 * the insertion of new nodes. There are no nodes with duplicate
 * priorites on the list.
 *
 * The nodes on the node_list are ordered by priority and can contain
 * entries which have the same priority. Those entries are ordered
 * FIFO
 *
 * Addition means: look for the prio_list node in the prio_list
 * for the priority of the node and insert it before the node_list
 * entry of the next prio_list node. If it is the first node of
 * that priority, add it to the prio_list in the right position and
 * insert it into the serialized node_list list
 *
 * Removal means remove it from the node_list and remove it from
 * the prio_list if the node_list list_head is non empty. In case
 * of removal from the prio_list it must be checked whether other
 * entries of the same priority are on the list or not. If there
 * is another entry of the same priority then this entry has to
 * replace the removed entry on the prio_list. If the entry which
 * is removed is the only entry of this priority then a simple
 * remove from both list is sufficient.
 *
 * INT_MIN is the highest priority, 0 is the medium highest, INT_MAX
 * is lowest priority.
 *
 * No locking is done, up to the caller.
 *
 */
#ifndef _LINUX_PLIST_H_
#define _LINUX_PLIST_H_

#include <linux/kernel.h>
#include <linux/list.h>

struct plist_head {
    struct list_head node_list;
};

struct plist_node {
    int         prio;
    struct list_head    prio_list;
    struct list_head    node_list;
};

#define PLIST_HEAD_INIT(head)               \
{                           \
    .node_list = LIST_HEAD_INIT((head).node_list)   \
}

#define PLIST_NODE_INIT(node, __prio)           \
{                           \
    .prio  = (__prio),              \
    .prio_list = LIST_HEAD_INIT((node).prio_list),  \
    .node_list = LIST_HEAD_INIT((node).node_list),  \
}

static inline void
plist_head_init(struct plist_head *head)
{
    INIT_LIST_HEAD(&head->node_list);
}

static inline void plist_node_init(struct plist_node *node, int prio)
{
    node->prio = prio;
    INIT_LIST_HEAD(&node->prio_list);
    INIT_LIST_HEAD(&node->node_list);
}

extern void plist_add(struct plist_node *node, struct plist_head *head);
extern void plist_del(struct plist_node *node, struct plist_head *head);

#define plist_for_each(pos, head)   \
     list_for_each_entry(pos, &(head)->node_list, node_list)

#define plist_for_each_safe(pos, n, head)   \
     list_for_each_entry_safe(pos, n, &(head)->node_list, node_list)

#define plist_for_each_entry(pos, head, mem)    \
     list_for_each_entry(pos, &(head)->node_list, mem.node_list)

#define plist_for_each_entry_safe(pos, n, head, m)  \
    list_for_each_entry_safe(pos, n, &(head)->node_list, m.node_list)

static inline int plist_head_empty(const struct plist_head *head)
{
    return list_empty(&head->node_list);
}

static inline int plist_node_empty(const struct plist_node *node)
{
    return list_empty(&node->node_list);
}

/* All functions below assume the plist_head is not empty. */

#ifdef CONFIG_DEBUG_PI_LIST
# define plist_first_entry(head, type, member)  \
({ \
    WARN_ON(plist_head_empty(head)); \
    container_of(plist_first(head), type, member); \
})
#else
# define plist_first_entry(head, type, member)  \
    container_of(plist_first(head), type, member)
#endif

#ifdef CONFIG_DEBUG_PI_LIST
# define plist_last_entry(head, type, member)   \
({ \
    WARN_ON(plist_head_empty(head)); \
    container_of(plist_last(head), type, member); \
})
#else
# define plist_last_entry(head, type, member)   \
    container_of(plist_last(head), type, member)
#endif

static inline struct plist_node *plist_first(const struct plist_head *head)
{
    return list_entry(head->node_list.next,
              struct plist_node, node_list);
}

static inline struct plist_node *plist_last(const struct plist_head *head)
{
    return list_entry(head->node_list.prev,
              struct plist_node, node_list);
}

#endif