Mac Easy 2010 May/Mac Life Ubuntu.iso/casper/filesystem.squashfs/usr/src/linux-headers-2.6.28-15/include/linux/rculist.h

C/C++ Source or Header | 2008-12-24 | 12.4 KB | 388 lines

#ifndef _LINUX_RCULIST_H
#define _LINUX_RCULIST_H

#ifdef __KERNEL__

/*
 * RCU-protected list version
 */
#include <linux/list.h>
#include <linux/rcupdate.h>

/*
 * Insert a new entry between two known consecutive entries.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_add_rcu(struct list_head *new,
        struct list_head *prev, struct list_head *next)
{
    new->next = next;
    new->prev = prev;
    rcu_assign_pointer(prev->next, new);
    next->prev = new;
}

/**
 * list_add_rcu - add a new entry to rcu-protected list
 * @new: new entry to be added
 * @head: list head to add it after
 *
 * Insert a new entry after the specified head.
 * This is good for implementing stacks.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as list_add_rcu()
 * or list_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * list_for_each_entry_rcu().
 */
static inline void list_add_rcu(struct list_head *new, struct list_head *head)
{
    __list_add_rcu(new, head, head->next);
}

/**
 * list_add_tail_rcu - add a new entry to rcu-protected list
 * @new: new entry to be added
 * @head: list head to add it before
 *
 * Insert a new entry before the specified head.
 * This is useful for implementing queues.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as list_add_tail_rcu()
 * or list_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * list_for_each_entry_rcu().
 */
static inline void list_add_tail_rcu(struct list_head *new,
                    struct list_head *head)
{
    __list_add_rcu(new, head->prev, head);
}

/**
 * list_del_rcu - deletes entry from list without re-initialization
 * @entry: the element to delete from the list.
 *
 * Note: list_empty() on entry does not return true after this,
 * the entry is in an undefined state. It is useful for RCU based
 * lockfree traversal.
 *
 * In particular, it means that we can not poison the forward
 * pointers that may still be used for walking the list.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as list_del_rcu()
 * or list_add_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * list_for_each_entry_rcu().
 *
 * Note that the caller is not permitted to immediately free
 * the newly deleted entry.  Instead, either synchronize_rcu()
 * or call_rcu() must be used to defer freeing until an RCU
 * grace period has elapsed.
 */
static inline void list_del_rcu(struct list_head *entry)
{
    __list_del(entry->prev, entry->next);
    entry->prev = LIST_POISON2;
}

/**
 * hlist_del_init_rcu - deletes entry from hash list with re-initialization
 * @n: the element to delete from the hash list.
 *
 * Note: list_unhashed() on the node return true after this. It is
 * useful for RCU based read lockfree traversal if the writer side
 * must know if the list entry is still hashed or already unhashed.
 *
 * In particular, it means that we can not poison the forward pointers
 * that may still be used for walking the hash list and we can only
 * zero the pprev pointer so list_unhashed() will return true after
 * this.
 *
 * The caller must take whatever precautions are necessary (such as
 * holding appropriate locks) to avoid racing with another
 * list-mutation primitive, such as hlist_add_head_rcu() or
 * hlist_del_rcu(), running on this same list.  However, it is
 * perfectly legal to run concurrently with the _rcu list-traversal
 * primitives, such as hlist_for_each_entry_rcu().
 */
static inline void hlist_del_init_rcu(struct hlist_node *n)
{
    if (!hlist_unhashed(n)) {
        __hlist_del(n);
        n->pprev = NULL;
    }
}

/**
 * list_replace_rcu - replace old entry by new one
 * @old : the element to be replaced
 * @new : the new element to insert
 *
 * The @old entry will be replaced with the @new entry atomically.
 * Note: @old should not be empty.
 */
static inline void list_replace_rcu(struct list_head *old,
                struct list_head *new)
{
    new->next = old->next;
    new->prev = old->prev;
    rcu_assign_pointer(new->prev->next, new);
    new->next->prev = new;
    old->prev = LIST_POISON2;
}

/**
 * list_splice_init_rcu - splice an RCU-protected list into an existing list.
 * @list:    the RCU-protected list to splice
 * @head:    the place in the list to splice the first list into
 * @sync:    function to sync: synchronize_rcu(), synchronize_sched(), ...
 *
 * @head can be RCU-read traversed concurrently with this function.
 *
 * Note that this function blocks.
 *
 * Important note: the caller must take whatever action is necessary to
 *    prevent any other updates to @head.  In principle, it is possible
 *    to modify the list as soon as sync() begins execution.
 *    If this sort of thing becomes necessary, an alternative version
 *    based on call_rcu() could be created.  But only if -really-
 *    needed -- there is no shortage of RCU API members.
 */
static inline void list_splice_init_rcu(struct list_head *list,
                    struct list_head *head,
                    void (*sync)(void))
{
    struct list_head *first = list->next;
    struct list_head *last = list->prev;
    struct list_head *at = head->next;

    if (list_empty(head))
        return;

    /* "first" and "last" tracking list, so initialize it. */

    INIT_LIST_HEAD(list);

    /*
     * At this point, the list body still points to the source list.
     * Wait for any readers to finish using the list before splicing
     * the list body into the new list.  Any new readers will see
     * an empty list.
     */

    sync();

    /*
     * Readers are finished with the source list, so perform splice.
     * The order is important if the new list is global and accessible
     * to concurrent RCU readers.  Note that RCU readers are not
     * permitted to traverse the prev pointers without excluding
     * this function.
     */

    last->next = at;
    rcu_assign_pointer(head->next, first);
    first->prev = head;
    at->prev = last;
}

#define __list_for_each_rcu(pos, head) \
    for (pos = rcu_dereference((head)->next); \
        pos != (head); \
        pos = rcu_dereference(pos->next))

/**
 * list_for_each_entry_rcu    -    iterate over rcu list of given type
 * @pos:    the type * to use as a loop cursor.
 * @head:    the head for your list.
 * @member:    the name of the list_struct within the struct.
 *
 * This list-traversal primitive may safely run concurrently with
 * the _rcu list-mutation primitives such as list_add_rcu()
 * as long as the traversal is guarded by rcu_read_lock().
 */
#define list_for_each_entry_rcu(pos, head, member) \
    for (pos = list_entry(rcu_dereference((head)->next), typeof(*pos), member); \
        prefetch(pos->member.next), &pos->member != (head); \
        pos = list_entry(rcu_dereference(pos->member.next), typeof(*pos), member))


/**
 * list_for_each_continue_rcu
 * @pos:    the &struct list_head to use as a loop cursor.
 * @head:    the head for your list.
 *
 * Iterate over an rcu-protected list, continuing after current point.
 *
 * This list-traversal primitive may safely run concurrently with
 * the _rcu list-mutation primitives such as list_add_rcu()
 * as long as the traversal is guarded by rcu_read_lock().
 */
#define list_for_each_continue_rcu(pos, head) \
    for ((pos) = rcu_dereference((pos)->next); \
        prefetch((pos)->next), (pos) != (head); \
        (pos) = rcu_dereference((pos)->next))

/**
 * hlist_del_rcu - deletes entry from hash list without re-initialization
 * @n: the element to delete from the hash list.
 *
 * Note: list_unhashed() on entry does not return true after this,
 * the entry is in an undefined state. It is useful for RCU based
 * lockfree traversal.
 *
 * In particular, it means that we can not poison the forward
 * pointers that may still be used for walking the hash list.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as hlist_add_head_rcu()
 * or hlist_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * hlist_for_each_entry().
 */
static inline void hlist_del_rcu(struct hlist_node *n)
{
    __hlist_del(n);
    n->pprev = LIST_POISON2;
}

/**
 * hlist_replace_rcu - replace old entry by new one
 * @old : the element to be replaced
 * @new : the new element to insert
 *
 * The @old entry will be replaced with the @new entry atomically.
 */
static inline void hlist_replace_rcu(struct hlist_node *old,
                    struct hlist_node *new)
{
    struct hlist_node *next = old->next;

    new->next = next;
    new->pprev = old->pprev;
    rcu_assign_pointer(*new->pprev, new);
    if (next)
        new->next->pprev = &new->next;
    old->pprev = LIST_POISON2;
}

/**
 * hlist_add_head_rcu
 * @n: the element to add to the hash list.
 * @h: the list to add to.
 *
 * Description:
 * Adds the specified element to the specified hlist,
 * while permitting racing traversals.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as hlist_add_head_rcu()
 * or hlist_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * hlist_for_each_entry_rcu(), used to prevent memory-consistency
 * problems on Alpha CPUs.  Regardless of the type of CPU, the
 * list-traversal primitive must be guarded by rcu_read_lock().
 */
static inline void hlist_add_head_rcu(struct hlist_node *n,
                    struct hlist_head *h)
{
    struct hlist_node *first = h->first;

    n->next = first;
    n->pprev = &h->first;
    rcu_assign_pointer(h->first, n);
    if (first)
        first->pprev = &n->next;
}

/**
 * hlist_add_before_rcu
 * @n: the new element to add to the hash list.
 * @next: the existing element to add the new element before.
 *
 * Description:
 * Adds the specified element to the specified hlist
 * before the specified node while permitting racing traversals.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as hlist_add_head_rcu()
 * or hlist_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * hlist_for_each_entry_rcu(), used to prevent memory-consistency
 * problems on Alpha CPUs.
 */
static inline void hlist_add_before_rcu(struct hlist_node *n,
                    struct hlist_node *next)
{
    n->pprev = next->pprev;
    n->next = next;
    rcu_assign_pointer(*(n->pprev), n);
    next->pprev = &n->next;
}

/**
 * hlist_add_after_rcu
 * @prev: the existing element to add the new element after.
 * @n: the new element to add to the hash list.
 *
 * Description:
 * Adds the specified element to the specified hlist
 * after the specified node while permitting racing traversals.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as hlist_add_head_rcu()
 * or hlist_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * hlist_for_each_entry_rcu(), used to prevent memory-consistency
 * problems on Alpha CPUs.
 */
static inline void hlist_add_after_rcu(struct hlist_node *prev,
                       struct hlist_node *n)
{
    n->next = prev->next;
    n->pprev = &prev->next;
    rcu_assign_pointer(prev->next, n);
    if (n->next)
        n->next->pprev = &n->next;
}

/**
 * hlist_for_each_entry_rcu - iterate over rcu list of given type
 * @tpos:    the type * to use as a loop cursor.
 * @pos:    the &struct hlist_node to use as a loop cursor.
 * @head:    the head for your list.
 * @member:    the name of the hlist_node within the struct.
 *
 * This list-traversal primitive may safely run concurrently with
 * the _rcu list-mutation primitives such as hlist_add_head_rcu()
 * as long as the traversal is guarded by rcu_read_lock().
 */
#define hlist_for_each_entry_rcu(tpos, pos, head, member)         \
    for (pos = rcu_dereference((head)->first);             \
        pos && ({ prefetch(pos->next); 1; }) &&             \
        ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \
        pos = rcu_dereference(pos->next))

#endif    /* __KERNEL__ */
#endif