1#ifndef _LINUX_LIST_BL_H
2#define _LINUX_LIST_BL_H
3
4#include <linux/list.h>
5#include <linux/bit_spinlock.h>
6
7/*
8 * Special version of lists, where head of the list has a lock in the lowest
9 * bit. This is useful for scalable hash tables without increasing memory
10 * footprint overhead.
11 *
12 * For modification operations, the 0 bit of hlist_bl_head->first
13 * pointer must be set.
14 *
15 * With some small modifications, this can easily be adapted to store several
16 * arbitrary bits (not just a single lock bit), if the need arises to store
17 * some fast and compact auxiliary data.
18 */
19
20#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
21#define LIST_BL_LOCKMASK	1UL
22#else
23#define LIST_BL_LOCKMASK	0UL
24#endif
25
26#ifdef CONFIG_DEBUG_LIST
27#define LIST_BL_BUG_ON(x) BUG_ON(x)
28#else
29#define LIST_BL_BUG_ON(x)
30#endif
31
32
33struct hlist_bl_head {
34	struct hlist_bl_node *first;
35};
36
37struct hlist_bl_node {
38	struct hlist_bl_node *next, **pprev;
39};
40#define INIT_HLIST_BL_HEAD(ptr) \
41	((ptr)->first = NULL)
42
43static inline void INIT_HLIST_BL_NODE(struct hlist_bl_node *h)
44{
45	h->next = NULL;
46	h->pprev = NULL;
47}
48
49#define hlist_bl_entry(ptr, type, member) container_of(ptr,type,member)
50
51static inline int hlist_bl_unhashed(const struct hlist_bl_node *h)
52{
53	return !h->pprev;
54}
55
56static inline struct hlist_bl_node *hlist_bl_first(struct hlist_bl_head *h)
57{
58	return (struct hlist_bl_node *)
59		((unsigned long)h->first & ~LIST_BL_LOCKMASK);
60}
61
62static inline void hlist_bl_set_first(struct hlist_bl_head *h,
63					struct hlist_bl_node *n)
64{
65	LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
66	LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
67							LIST_BL_LOCKMASK);
68	h->first = (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK);
69}
70
71static inline int hlist_bl_empty(const struct hlist_bl_head *h)
72{
73	return !((unsigned long)h->first & ~LIST_BL_LOCKMASK);
74}
75
76static inline void hlist_bl_add_head(struct hlist_bl_node *n,
77					struct hlist_bl_head *h)
78{
79	struct hlist_bl_node *first = hlist_bl_first(h);
80
81	n->next = first;
82	if (first)
83		first->pprev = &n->next;
84	n->pprev = &h->first;
85	hlist_bl_set_first(h, n);
86}
87
88static inline void __hlist_bl_del(struct hlist_bl_node *n)
89{
90	struct hlist_bl_node *next = n->next;
91	struct hlist_bl_node **pprev = n->pprev;
92
93	LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
94
95	/* pprev may be `first`, so be careful not to lose the lock bit */
96	*pprev = (struct hlist_bl_node *)
97			((unsigned long)next |
98			 ((unsigned long)*pprev & LIST_BL_LOCKMASK));
99	if (next)
100		next->pprev = pprev;
101}
102
103static inline void hlist_bl_del(struct hlist_bl_node *n)
104{
105	__hlist_bl_del(n);
106	n->next = LIST_POISON1;
107	n->pprev = LIST_POISON2;
108}
109
110static inline void hlist_bl_del_init(struct hlist_bl_node *n)
111{
112	if (!hlist_bl_unhashed(n)) {
113		__hlist_bl_del(n);
114		INIT_HLIST_BL_NODE(n);
115	}
116}
117
118static inline void hlist_bl_lock(struct hlist_bl_head *b)
119{
120	bit_spin_lock(0, (unsigned long *)b);
121}
122
123static inline void hlist_bl_unlock(struct hlist_bl_head *b)
124{
125	__bit_spin_unlock(0, (unsigned long *)b);
126}
127
128static inline bool hlist_bl_is_locked(struct hlist_bl_head *b)
129{
130	return bit_spin_is_locked(0, (unsigned long *)b);
131}
132
133/**
134 * hlist_bl_for_each_entry	- iterate over list of given type
135 * @tpos:	the type * to use as a loop cursor.
136 * @pos:	the &struct hlist_node to use as a loop cursor.
137 * @head:	the head for your list.
138 * @member:	the name of the hlist_node within the struct.
139 *
140 */
141#define hlist_bl_for_each_entry(tpos, pos, head, member)		\
142	for (pos = hlist_bl_first(head);				\
143	     pos &&							\
144		({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \
145	     pos = pos->next)
146
147/**
148 * hlist_bl_for_each_entry_safe - iterate over list of given type safe against removal of list entry
149 * @tpos:	the type * to use as a loop cursor.
150 * @pos:	the &struct hlist_node to use as a loop cursor.
151 * @n:		another &struct hlist_node to use as temporary storage
152 * @head:	the head for your list.
153 * @member:	the name of the hlist_node within the struct.
154 */
155#define hlist_bl_for_each_entry_safe(tpos, pos, n, head, member)	 \
156	for (pos = hlist_bl_first(head);				 \
157	     pos && ({ n = pos->next; 1; }) && 				 \
158		({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \
159	     pos = n)
160
161#endif
162