LXR linux/include/linux/rculist

   1/* SPDX-License-Identifier: GPL-2.0 */
   2#ifndef _LINUX_RCULIST_BL_H
   3#define _LINUX_RCULIST_BL_H
   4
   5/*
   6 * RCU-protected bl list version. See include/linux/list_bl.h.
   7 */
   8#include <linux/list_bl.h>
   9#include <linux/rcupdate.h>
  10
  11static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
  12                                        struct hlist_bl_node *n)
  13{
  14        LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
  15        LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
  16                                                        LIST_BL_LOCKMASK);
  17        rcu_assign_pointer(h->first,
  18                (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
  19}
  20
  21static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h)
  22{
  23        return (struct hlist_bl_node *)
  24                ((unsigned long)rcu_dereference_check(h->first, hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK);
  25}
  26
  27/**
  28 * hlist_bl_del_init_rcu - deletes entry from hash list with re-initialization
  29 * @n: the element to delete from the hash list.
  30 *
  31 * Note: hlist_bl_unhashed() on the node returns true after this. It is
  32 * useful for RCU based read lockfree traversal if the writer side
  33 * must know if the list entry is still hashed or already unhashed.
  34 *
  35 * In particular, it means that we can not poison the forward pointers
  36 * that may still be used for walking the hash list and we can only
  37 * zero the pprev pointer so list_unhashed() will return true after
  38 * this.
  39 *
  40 * The caller must take whatever precautions are necessary (such as
  41 * holding appropriate locks) to avoid racing with another
  42 * list-mutation primitive, such as hlist_bl_add_head_rcu() or
  43 * hlist_bl_del_rcu(), running on this same list.  However, it is
  44 * perfectly legal to run concurrently with the _rcu list-traversal
  45 * primitives, such as hlist_bl_for_each_entry_rcu().
  46 */
  47static inline void hlist_bl_del_init_rcu(struct hlist_bl_node *n)
  48{
  49        if (!hlist_bl_unhashed(n)) {
  50                __hlist_bl_del(n);
  51                n->pprev = NULL;
  52        }
  53}
  54
  55/**
  56 * hlist_bl_del_rcu - deletes entry from hash list without re-initialization
  57 * @n: the element to delete from the hash list.
  58 *
  59 * Note: hlist_bl_unhashed() on entry does not return true after this,
  60 * the entry is in an undefined state. It is useful for RCU based
  61 * lockfree traversal.
  62 *
  63 * In particular, it means that we can not poison the forward
  64 * pointers that may still be used for walking the hash list.
  65 *
  66 * The caller must take whatever precautions are necessary
  67 * (such as holding appropriate locks) to avoid racing
  68 * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
  69 * or hlist_bl_del_rcu(), running on this same list.
  70 * However, it is perfectly legal to run concurrently with
  71 * the _rcu list-traversal primitives, such as
  72 * hlist_bl_for_each_entry().
  73 */
  74static inline void hlist_bl_del_rcu(struct hlist_bl_node *n)
  75{
  76        __hlist_bl_del(n);
  77        n->pprev = LIST_POISON2;
  78}
  79
  80/**
  81 * hlist_bl_add_head_rcu
  82 * @n: the element to add to the hash list.
  83 * @h: the list to add to.
  84 *
  85 * Description:
  86 * Adds the specified element to the specified hlist_bl,
  87 * while permitting racing traversals.
  88 *
  89 * The caller must take whatever precautions are necessary
  90 * (such as holding appropriate locks) to avoid racing
  91 * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
  92 * or hlist_bl_del_rcu(), running on this same list.
  93 * However, it is perfectly legal to run concurrently with
  94 * the _rcu list-traversal primitives, such as
  95 * hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency
  96 * problems on Alpha CPUs.  Regardless of the type of CPU, the
  97 * list-traversal primitive must be guarded by rcu_read_lock().
  98 */
  99static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n,
 100                                        struct hlist_bl_head *h)
 101{
 102        struct hlist_bl_node *first;
 103
 104        /* don't need hlist_bl_first_rcu because we're under lock */
 105        first = hlist_bl_first(h);
 106
 107        n->next = first;
 108        if (first)
 109                first->pprev = &n->next;
 110        n->pprev = &h->first;
 111
 112        /* need _rcu because we can have concurrent lock free readers */
 113        hlist_bl_set_first_rcu(h, n);
 114}
 115/**
 116 * hlist_bl_for_each_entry_rcu - iterate over rcu list of given type
 117 * @tpos:       the type * to use as a loop cursor.
 118 * @pos:        the &struct hlist_bl_node to use as a loop cursor.
 119 * @head:       the head for your list.
 120 * @member:     the name of the hlist_bl_node within the struct.
 121 *
 122 */
 123#define hlist_bl_for_each_entry_rcu(tpos, pos, head, member)            \
 124        for (pos = hlist_bl_first_rcu(head);                            \
 125                pos &&                                                  \
 126                ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
 127                pos = rcu_dereference_raw(pos->next))
 128
 129#endif
 130