linux/include/linux/rculist_bl.h
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   1#ifndef _LINUX_RCULIST_BL_H
   2#define _LINUX_RCULIST_BL_H
   3
   4/*
   5 * RCU-protected bl list version. See include/linux/list_bl.h.
   6 */
   7#include <linux/list_bl.h>
   8#include <linux/rcupdate.h>
   9
  10static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
  11                                        struct hlist_bl_node *n)
  12{
  13        LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
  14        LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
  15                                                        LIST_BL_LOCKMASK);
  16        rcu_assign_pointer(h->first,
  17                (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
  18}
  19
  20static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h)
  21{
  22        return (struct hlist_bl_node *)
  23                ((unsigned long)rcu_dereference(h->first) & ~LIST_BL_LOCKMASK);
  24}
  25
  26/**
  27 * hlist_bl_del_init_rcu - deletes entry from hash list with re-initialization
  28 * @n: the element to delete from the hash list.
  29 *
  30 * Note: hlist_bl_unhashed() on the node returns true after this. It is
  31 * useful for RCU based read lockfree traversal if the writer side
  32 * must know if the list entry is still hashed or already unhashed.
  33 *
  34 * In particular, it means that we can not poison the forward pointers
  35 * that may still be used for walking the hash list and we can only
  36 * zero the pprev pointer so list_unhashed() will return true after
  37 * this.
  38 *
  39 * The caller must take whatever precautions are necessary (such as
  40 * holding appropriate locks) to avoid racing with another
  41 * list-mutation primitive, such as hlist_bl_add_head_rcu() or
  42 * hlist_bl_del_rcu(), running on this same list.  However, it is
  43 * perfectly legal to run concurrently with the _rcu list-traversal
  44 * primitives, such as hlist_bl_for_each_entry_rcu().
  45 */
  46static inline void hlist_bl_del_init_rcu(struct hlist_bl_node *n)
  47{
  48        if (!hlist_bl_unhashed(n)) {
  49                __hlist_bl_del(n);
  50                n->pprev = NULL;
  51        }
  52}
  53
  54/**
  55 * hlist_bl_del_rcu - deletes entry from hash list without re-initialization
  56 * @n: the element to delete from the hash list.
  57 *
  58 * Note: hlist_bl_unhashed() on entry does not return true after this,
  59 * the entry is in an undefined state. It is useful for RCU based
  60 * lockfree traversal.
  61 *
  62 * In particular, it means that we can not poison the forward
  63 * pointers that may still be used for walking the hash list.
  64 *
  65 * The caller must take whatever precautions are necessary
  66 * (such as holding appropriate locks) to avoid racing
  67 * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
  68 * or hlist_bl_del_rcu(), running on this same list.
  69 * However, it is perfectly legal to run concurrently with
  70 * the _rcu list-traversal primitives, such as
  71 * hlist_bl_for_each_entry().
  72 */
  73static inline void hlist_bl_del_rcu(struct hlist_bl_node *n)
  74{
  75        __hlist_bl_del(n);
  76        n->pprev = LIST_POISON2;
  77}
  78
  79/**
  80 * hlist_bl_add_head_rcu
  81 * @n: the element to add to the hash list.
  82 * @h: the list to add to.
  83 *
  84 * Description:
  85 * Adds the specified element to the specified hlist_bl,
  86 * while permitting racing traversals.
  87 *
  88 * The caller must take whatever precautions are necessary
  89 * (such as holding appropriate locks) to avoid racing
  90 * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
  91 * or hlist_bl_del_rcu(), running on this same list.
  92 * However, it is perfectly legal to run concurrently with
  93 * the _rcu list-traversal primitives, such as
  94 * hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency
  95 * problems on Alpha CPUs.  Regardless of the type of CPU, the
  96 * list-traversal primitive must be guarded by rcu_read_lock().
  97 */
  98static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n,
  99                                        struct hlist_bl_head *h)
 100{
 101        struct hlist_bl_node *first;
 102
 103        /* don't need hlist_bl_first_rcu because we're under lock */
 104        first = hlist_bl_first(h);
 105
 106        n->next = first;
 107        if (first)
 108                first->pprev = &n->next;
 109        n->pprev = &h->first;
 110
 111        /* need _rcu because we can have concurrent lock free readers */
 112        hlist_bl_set_first_rcu(h, n);
 113}
 114/**
 115 * hlist_bl_for_each_entry_rcu - iterate over rcu list of given type
 116 * @tpos:       the type * to use as a loop cursor.
 117 * @pos:        the &struct hlist_bl_node to use as a loop cursor.
 118 * @head:       the head for your list.
 119 * @member:     the name of the hlist_bl_node within the struct.
 120 *
 121 */
 122#define hlist_bl_for_each_entry_rcu(tpos, pos, head, member)            \
 123        for (pos = hlist_bl_first_rcu(head);                            \
 124                pos &&                                                  \
 125                ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
 126                pos = rcu_dereference_raw(pos->next))
 127
 128#endif
 129
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