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_check(h->first, hlist_bl_is_locked(h)) & ~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