1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | #ifndef _LINUX_LIST_BL_H |
3 | #define _LINUX_LIST_BL_H |
4 | |
5 | #include <linux/list.h> |
6 | #include <linux/bit_spinlock.h> |
7 | |
8 | /* |
9 | * Special version of lists, where head of the list has a lock in the lowest |
10 | * bit. This is useful for scalable hash tables without increasing memory |
11 | * footprint overhead. |
12 | * |
13 | * For modification operations, the 0 bit of hlist_bl_head->first |
14 | * pointer must be set. |
15 | * |
16 | * With some small modifications, this can easily be adapted to store several |
17 | * arbitrary bits (not just a single lock bit), if the need arises to store |
18 | * some fast and compact auxiliary data. |
19 | */ |
20 | |
21 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
22 | #define LIST_BL_LOCKMASK 1UL |
23 | #else |
24 | #define LIST_BL_LOCKMASK 0UL |
25 | #endif |
26 | |
27 | #ifdef CONFIG_DEBUG_LIST |
28 | #define LIST_BL_BUG_ON(x) BUG_ON(x) |
29 | #else |
30 | #define LIST_BL_BUG_ON(x) |
31 | #endif |
32 | |
33 | |
34 | struct hlist_bl_head { |
35 | struct hlist_bl_node *first; |
36 | }; |
37 | |
38 | struct hlist_bl_node { |
39 | struct hlist_bl_node *next, **pprev; |
40 | }; |
41 | #define INIT_HLIST_BL_HEAD(ptr) \ |
42 | ((ptr)->first = NULL) |
43 | |
44 | static inline void INIT_HLIST_BL_NODE(struct hlist_bl_node *h) |
45 | { |
46 | h->next = NULL; |
47 | h->pprev = NULL; |
48 | } |
49 | |
50 | #define hlist_bl_entry(ptr, type, member) container_of(ptr,type,member) |
51 | |
52 | static inline bool hlist_bl_unhashed(const struct hlist_bl_node *h) |
53 | { |
54 | return !h->pprev; |
55 | } |
56 | |
57 | static inline struct hlist_bl_node *hlist_bl_first(struct hlist_bl_head *h) |
58 | { |
59 | return (struct hlist_bl_node *) |
60 | ((unsigned long)h->first & ~LIST_BL_LOCKMASK); |
61 | } |
62 | |
63 | static inline void hlist_bl_set_first(struct hlist_bl_head *h, |
64 | struct hlist_bl_node *n) |
65 | { |
66 | LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK); |
67 | LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) != |
68 | LIST_BL_LOCKMASK); |
69 | h->first = (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK); |
70 | } |
71 | |
72 | static inline bool hlist_bl_empty(const struct hlist_bl_head *h) |
73 | { |
74 | return !((unsigned long)READ_ONCE(h->first) & ~LIST_BL_LOCKMASK); |
75 | } |
76 | |
77 | static inline void hlist_bl_add_head(struct hlist_bl_node *n, |
78 | struct hlist_bl_head *h) |
79 | { |
80 | struct hlist_bl_node *first = hlist_bl_first(h); |
81 | |
82 | n->next = first; |
83 | if (first) |
84 | first->pprev = &n->next; |
85 | n->pprev = &h->first; |
86 | hlist_bl_set_first(h, n); |
87 | } |
88 | |
89 | static inline void hlist_bl_add_before(struct hlist_bl_node *n, |
90 | struct hlist_bl_node *next) |
91 | { |
92 | struct hlist_bl_node **pprev = next->pprev; |
93 | |
94 | n->pprev = pprev; |
95 | n->next = next; |
96 | next->pprev = &n->next; |
97 | |
98 | /* pprev may be `first`, so be careful not to lose the lock bit */ |
99 | WRITE_ONCE(*pprev, |
100 | (struct hlist_bl_node *) |
101 | ((uintptr_t)n | ((uintptr_t)*pprev & LIST_BL_LOCKMASK))); |
102 | } |
103 | |
104 | static inline void hlist_bl_add_behind(struct hlist_bl_node *n, |
105 | struct hlist_bl_node *prev) |
106 | { |
107 | n->next = prev->next; |
108 | n->pprev = &prev->next; |
109 | prev->next = n; |
110 | |
111 | if (n->next) |
112 | n->next->pprev = &n->next; |
113 | } |
114 | |
115 | static inline void __hlist_bl_del(struct hlist_bl_node *n) |
116 | { |
117 | struct hlist_bl_node *next = n->next; |
118 | struct hlist_bl_node **pprev = n->pprev; |
119 | |
120 | LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK); |
121 | |
122 | /* pprev may be `first`, so be careful not to lose the lock bit */ |
123 | WRITE_ONCE(*pprev, |
124 | (struct hlist_bl_node *) |
125 | ((unsigned long)next | |
126 | ((unsigned long)*pprev & LIST_BL_LOCKMASK))); |
127 | if (next) |
128 | next->pprev = pprev; |
129 | } |
130 | |
131 | static inline void hlist_bl_del(struct hlist_bl_node *n) |
132 | { |
133 | __hlist_bl_del(n); |
134 | n->next = LIST_POISON1; |
135 | n->pprev = LIST_POISON2; |
136 | } |
137 | |
138 | static inline void hlist_bl_del_init(struct hlist_bl_node *n) |
139 | { |
140 | if (!hlist_bl_unhashed(h: n)) { |
141 | __hlist_bl_del(n); |
142 | INIT_HLIST_BL_NODE(h: n); |
143 | } |
144 | } |
145 | |
146 | static inline void hlist_bl_lock(struct hlist_bl_head *b) |
147 | { |
148 | bit_spin_lock(bitnum: 0, addr: (unsigned long *)b); |
149 | } |
150 | |
151 | static inline void hlist_bl_unlock(struct hlist_bl_head *b) |
152 | { |
153 | __bit_spin_unlock(bitnum: 0, addr: (unsigned long *)b); |
154 | } |
155 | |
156 | static inline bool hlist_bl_is_locked(struct hlist_bl_head *b) |
157 | { |
158 | return bit_spin_is_locked(bitnum: 0, addr: (unsigned long *)b); |
159 | } |
160 | |
161 | /** |
162 | * hlist_bl_for_each_entry - iterate over list of given type |
163 | * @tpos: the type * to use as a loop cursor. |
164 | * @pos: the &struct hlist_node to use as a loop cursor. |
165 | * @head: the head for your list. |
166 | * @member: the name of the hlist_node within the struct. |
167 | * |
168 | */ |
169 | #define hlist_bl_for_each_entry(tpos, pos, head, member) \ |
170 | for (pos = hlist_bl_first(head); \ |
171 | pos && \ |
172 | ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \ |
173 | pos = pos->next) |
174 | |
175 | /** |
176 | * hlist_bl_for_each_entry_safe - iterate over list of given type safe against removal of list entry |
177 | * @tpos: the type * to use as a loop cursor. |
178 | * @pos: the &struct hlist_node to use as a loop cursor. |
179 | * @n: another &struct hlist_node to use as temporary storage |
180 | * @head: the head for your list. |
181 | * @member: the name of the hlist_node within the struct. |
182 | */ |
183 | #define hlist_bl_for_each_entry_safe(tpos, pos, n, head, member) \ |
184 | for (pos = hlist_bl_first(head); \ |
185 | pos && ({ n = pos->next; 1; }) && \ |
186 | ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \ |
187 | pos = n) |
188 | |
189 | #endif |
190 | |