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_rcu - deletes entry from hash list without re-initialization
29 * @n: the element to delete from the hash list.
30 *
31 * Note: hlist_bl_unhashed() on entry does not return true after this,
32 * the entry is in an undefined state. It is useful for RCU based
33 * lockfree traversal.
34 *
35 * In particular, it means that we can not poison the forward
36 * pointers that may still be used for walking the hash list.
37 *
38 * The caller must take whatever precautions are necessary
39 * (such as holding appropriate locks) to avoid racing
40 * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
41 * or hlist_bl_del_rcu(), running on this same list.
42 * However, it is perfectly legal to run concurrently with
43 * the _rcu list-traversal primitives, such as
44 * hlist_bl_for_each_entry().
45 */
46static inline void hlist_bl_del_rcu(struct hlist_bl_node *n)
47{
48 __hlist_bl_del(n);
49 n->pprev = LIST_POISON2;
50}
51
52/**
53 * hlist_bl_add_head_rcu
54 * @n: the element to add to the hash list.
55 * @h: the list to add to.
56 *
57 * Description:
58 * Adds the specified element to the specified hlist_bl,
59 * while permitting racing traversals.
60 *
61 * The caller must take whatever precautions are necessary
62 * (such as holding appropriate locks) to avoid racing
63 * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
64 * or hlist_bl_del_rcu(), running on this same list.
65 * However, it is perfectly legal to run concurrently with
66 * the _rcu list-traversal primitives, such as
67 * hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency
68 * problems on Alpha CPUs. Regardless of the type of CPU, the
69 * list-traversal primitive must be guarded by rcu_read_lock().
70 */
71static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n,
72 struct hlist_bl_head *h)
73{
74 struct hlist_bl_node *first;
75
76 /* don't need hlist_bl_first_rcu because we're under lock */
77 first = hlist_bl_first(h);
78
79 n->next = first;
80 if (first)
81 first->pprev = &n->next;
82 n->pprev = &h->first;
83
84 /* need _rcu because we can have concurrent lock free readers */
85 hlist_bl_set_first_rcu(h, n);
86}
87/**
88 * hlist_bl_for_each_entry_rcu - iterate over rcu list of given type
89 * @tpos: the type * to use as a loop cursor.
90 * @pos: the &struct hlist_bl_node to use as a loop cursor.
91 * @head: the head for your list.
92 * @member: the name of the hlist_bl_node within the struct.
93 *
94 */
95#define hlist_bl_for_each_entry_rcu(tpos, pos, head, member) \
96 for (pos = hlist_bl_first_rcu(head); \
97 pos && \
98 ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
99 pos = rcu_dereference_raw(pos->next))
100
101#endif
102