list.h

xen虚拟机源代码安装包

 * Double linked lists with a single pointer list head.
 * Mostly useful for hash tables where the two pointer list head is
 * too wasteful.
 * You lose the ability to access the tail in O(1).
 */

struct hlist_head {
    struct hlist_node *first;
};

struct hlist_node {
    struct hlist_node *next, **pprev;
};

#define HLIST_HEAD_INIT { .first = NULL }
#define HLIST_HEAD(name) struct hlist_head name = {  .first = NULL }
#define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
static inline void INIT_HLIST_NODE(struct hlist_node *h)
{
    h->next = NULL;
    h->pprev = NULL;
}

static inline int hlist_unhashed(const struct hlist_node *h)
{
    return !h->pprev;
}

static inline int hlist_empty(const struct hlist_head *h)
{
    return !h->first;
}

static inline void __hlist_del(struct hlist_node *n)
{
    struct hlist_node *next = n->next;
    struct hlist_node **pprev = n->pprev;
    *pprev = next;
    if (next)
        next->pprev = pprev;
}

static inline void hlist_del(struct hlist_node *n)
{
    __hlist_del(n);
    n->next = LIST_POISON1;
    n->pprev = LIST_POISON2;
}

/**
 * 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;
}

static inline void hlist_del_init(struct hlist_node *n)
{
    if (!hlist_unhashed(n)) {
        __hlist_del(n);
        INIT_HLIST_NODE(n);
    }
}

/*
 * 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;
    smp_wmb();
    if (next)
        new->next->pprev = &new->next;
    *new->pprev = new;
    old->pprev = LIST_POISON2;
}

static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
{
    struct hlist_node *first = h->first;
    n->next = first;
    if (first)
        first->pprev = &n->next;
    h->first = n;
    n->pprev = &h->first;
}

/**
 * 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;
    smp_wmb();
    if (first)
        first->pprev = &n->next;
    h->first = n;
}

/* next must be != NULL */
static inline void hlist_add_before(struct hlist_node *n,
                    struct hlist_node *next)
{
    n->pprev = next->pprev;
    n->next = next;
    next->pprev = &n->next;
    *(n->pprev) = n;
}

static inline void hlist_add_after(struct hlist_node *n,
                    struct hlist_node *next)
{
    next->next = n->next;
    n->next = next;
    next->pprev = &n->next;

    if(next->next)
        next->next->pprev  = &next->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;
    smp_wmb();
    next->pprev = &n->next;
    *(n->pprev) = n;
}

/**
 * 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;
    smp_wmb();
    prev->next = n;
    if (n->next)
        n->next->pprev = &n->next;
}

#define hlist_entry(ptr, type, member) container_of(ptr,type,member)

#define hlist_for_each(pos, head)                                       \
    for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; });     \
         pos = pos->next)

#define hlist_for_each_safe(pos, n, head)                       \
    for (pos = (head)->first; pos && ({ n = pos->next; 1; });   \
         pos = n)

/**
 * hlist_for_each_entry    - iterate over 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.
 */
#define hlist_for_each_entry(tpos, pos, head, member)                   \
    for (pos = (head)->first;                                           \
         pos && ({ prefetch(pos->next); 1;}) &&                         \
         ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;});       \
         pos = pos->next)

/**
 * hlist_for_each_entry_continue - iterate over a hlist continuing
 *                                 after current point
 * @tpos:    the type * to use as a loop cursor.
 * @pos:    the &struct hlist_node to use as a loop cursor.
 * @member:    the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_continue(tpos, pos, member)                \
    for (pos = (pos)->next;                                             \
         pos && ({ prefetch(pos->next); 1;}) &&                         \
         ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;});       \
         pos = pos->next)

/**
 * hlist_for_each_entry_from - iterate over a hlist continuing from
 *                             current point
 * @tpos:    the type * to use as a loop cursor.
 * @pos:    the &struct hlist_node to use as a loop cursor.
 * @member:    the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_from(tpos, pos, member)                    \
    for (; pos && ({ prefetch(pos->next); 1;}) &&                       \
         ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;});       \
         pos = pos->next)

/**
 * hlist_for_each_entry_safe - iterate over list of given type safe
 *                             against removal of list entry
 * @tpos:    the type * to use as a loop cursor.
 * @pos:    the &struct hlist_node to use as a loop cursor.
 * @n:        another &struct hlist_node to use as temporary storage
 * @head:    the head for your list.
 * @member:    the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_safe(tpos, pos, n, head, member)           \
    for (pos = (head)->first;                                           \
         pos && ({ n = pos->next; 1; }) &&                              \
         ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;});       \
         pos = n)


/**
 * 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 = (head)->first;                                          \
          rcu_dereference(pos) && ({ prefetch(pos->next); 1;}) &&       \
          ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;});      \
          pos = pos->next)

#endif /* __XEN_LIST_H__ */