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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
bbaffaca ED |
2 | #ifndef _LINUX_RCULIST_NULLS_H |
3 | #define _LINUX_RCULIST_NULLS_H | |
4 | ||
5 | #ifdef __KERNEL__ | |
6 | ||
7 | /* | |
8 | * RCU-protected list version | |
9 | */ | |
10 | #include <linux/list_nulls.h> | |
11 | #include <linux/rcupdate.h> | |
12 | ||
13 | /** | |
14 | * hlist_nulls_del_init_rcu - deletes entry from hash list with re-initialization | |
15 | * @n: the element to delete from the hash list. | |
16 | * | |
17 | * Note: hlist_nulls_unhashed() on the node return true after this. It is | |
18 | * useful for RCU based read lockfree traversal if the writer side | |
19 | * must know if the list entry is still hashed or already unhashed. | |
20 | * | |
21 | * In particular, it means that we can not poison the forward pointers | |
22 | * that may still be used for walking the hash list and we can only | |
23 | * zero the pprev pointer so list_unhashed() will return true after | |
24 | * this. | |
25 | * | |
26 | * The caller must take whatever precautions are necessary (such as | |
27 | * holding appropriate locks) to avoid racing with another | |
28 | * list-mutation primitive, such as hlist_nulls_add_head_rcu() or | |
29 | * hlist_nulls_del_rcu(), running on this same list. However, it is | |
30 | * perfectly legal to run concurrently with the _rcu list-traversal | |
31 | * primitives, such as hlist_nulls_for_each_entry_rcu(). | |
32 | */ | |
33 | static inline void hlist_nulls_del_init_rcu(struct hlist_nulls_node *n) | |
34 | { | |
35 | if (!hlist_nulls_unhashed(n)) { | |
36 | __hlist_nulls_del(n); | |
860c8802 | 37 | WRITE_ONCE(n->pprev, NULL); |
bbaffaca ED |
38 | } |
39 | } | |
40 | ||
7f5d51e2 MB |
41 | /** |
42 | * hlist_nulls_first_rcu - returns the first element of the hash list. | |
43 | * @head: the head of the list. | |
44 | */ | |
67bdbffd AB |
45 | #define hlist_nulls_first_rcu(head) \ |
46 | (*((struct hlist_nulls_node __rcu __force **)&(head)->first)) | |
47 | ||
7f5d51e2 MB |
48 | /** |
49 | * hlist_nulls_next_rcu - returns the element of the list after @node. | |
50 | * @node: element of the list. | |
51 | */ | |
67bdbffd AB |
52 | #define hlist_nulls_next_rcu(node) \ |
53 | (*((struct hlist_nulls_node __rcu __force **)&(node)->next)) | |
54 | ||
bbaffaca ED |
55 | /** |
56 | * hlist_nulls_del_rcu - deletes entry from hash list without re-initialization | |
57 | * @n: the element to delete from the hash list. | |
58 | * | |
59 | * Note: hlist_nulls_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_nulls_add_head_rcu() | |
69 | * or hlist_nulls_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_nulls_for_each_entry(). | |
73 | */ | |
74 | static inline void hlist_nulls_del_rcu(struct hlist_nulls_node *n) | |
75 | { | |
76 | __hlist_nulls_del(n); | |
860c8802 | 77 | WRITE_ONCE(n->pprev, LIST_POISON2); |
bbaffaca ED |
78 | } |
79 | ||
80 | /** | |
81 | * hlist_nulls_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_nulls, | |
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_nulls_add_head_rcu() | |
92 | * or hlist_nulls_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_nulls_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 | */ | |
99 | static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n, | |
100 | struct hlist_nulls_head *h) | |
101 | { | |
102 | struct hlist_nulls_node *first = h->first; | |
103 | ||
efd04f8a | 104 | WRITE_ONCE(n->next, first); |
860c8802 | 105 | WRITE_ONCE(n->pprev, &h->first); |
67bdbffd | 106 | rcu_assign_pointer(hlist_nulls_first_rcu(h), n); |
bbaffaca | 107 | if (!is_a_nulls(first)) |
860c8802 | 108 | WRITE_ONCE(first->pprev, &n->next); |
bbaffaca | 109 | } |
d894ba18 | 110 | |
8dbd76e7 ED |
111 | /** |
112 | * hlist_nulls_add_tail_rcu | |
113 | * @n: the element to add to the hash list. | |
114 | * @h: the list to add to. | |
115 | * | |
116 | * Description: | |
117 | * Adds the specified element to the specified hlist_nulls, | |
118 | * while permitting racing traversals. | |
119 | * | |
120 | * The caller must take whatever precautions are necessary | |
121 | * (such as holding appropriate locks) to avoid racing | |
122 | * with another list-mutation primitive, such as hlist_nulls_add_head_rcu() | |
123 | * or hlist_nulls_del_rcu(), running on this same list. | |
124 | * However, it is perfectly legal to run concurrently with | |
125 | * the _rcu list-traversal primitives, such as | |
126 | * hlist_nulls_for_each_entry_rcu(), used to prevent memory-consistency | |
127 | * problems on Alpha CPUs. Regardless of the type of CPU, the | |
128 | * list-traversal primitive must be guarded by rcu_read_lock(). | |
129 | */ | |
130 | static inline void hlist_nulls_add_tail_rcu(struct hlist_nulls_node *n, | |
131 | struct hlist_nulls_head *h) | |
132 | { | |
133 | struct hlist_nulls_node *i, *last = NULL; | |
134 | ||
135 | /* Note: write side code, so rcu accessors are not needed. */ | |
136 | for (i = h->first; !is_a_nulls(i); i = i->next) | |
137 | last = i; | |
138 | ||
139 | if (last) { | |
efd04f8a | 140 | WRITE_ONCE(n->next, last->next); |
8dbd76e7 | 141 | n->pprev = &last->next; |
c004d231 | 142 | rcu_assign_pointer(hlist_nulls_next_rcu(last), n); |
8dbd76e7 ED |
143 | } else { |
144 | hlist_nulls_add_head_rcu(n, h); | |
145 | } | |
146 | } | |
147 | ||
6a757c07 FW |
148 | /* after that hlist_nulls_del will work */ |
149 | static inline void hlist_nulls_add_fake(struct hlist_nulls_node *n) | |
150 | { | |
151 | n->pprev = &n->next; | |
152 | n->next = (struct hlist_nulls_node *)NULLS_MARKER(NULL); | |
153 | } | |
154 | ||
bbaffaca ED |
155 | /** |
156 | * hlist_nulls_for_each_entry_rcu - iterate over rcu list of given type | |
157 | * @tpos: the type * to use as a loop cursor. | |
158 | * @pos: the &struct hlist_nulls_node to use as a loop cursor. | |
459b5287 | 159 | * @head: the head of the list. |
bbaffaca ED |
160 | * @member: the name of the hlist_nulls_node within the struct. |
161 | * | |
c87a124a ED |
162 | * The barrier() is needed to make sure compiler doesn't cache first element [1], |
163 | * as this loop can be restarted [2] | |
5bb1369d | 164 | * [1] Documentation/memory-barriers.txt around line 1533 |
2cdb54c9 | 165 | * [2] Documentation/RCU/rculist_nulls.rst around line 146 |
bbaffaca | 166 | */ |
67bdbffd | 167 | #define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \ |
c87a124a ED |
168 | for (({barrier();}), \ |
169 | pos = rcu_dereference_raw(hlist_nulls_first_rcu(head)); \ | |
67bdbffd | 170 | (!is_a_nulls(pos)) && \ |
bbaffaca | 171 | ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \ |
67bdbffd | 172 | pos = rcu_dereference_raw(hlist_nulls_next_rcu(pos))) |
bbaffaca | 173 | |
4fe84359 AS |
174 | /** |
175 | * hlist_nulls_for_each_entry_safe - | |
176 | * 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_nulls_node to use as a loop cursor. | |
459b5287 | 179 | * @head: the head of the list. |
4fe84359 AS |
180 | * @member: the name of the hlist_nulls_node within the struct. |
181 | */ | |
182 | #define hlist_nulls_for_each_entry_safe(tpos, pos, head, member) \ | |
183 | for (({barrier();}), \ | |
184 | pos = rcu_dereference_raw(hlist_nulls_first_rcu(head)); \ | |
185 | (!is_a_nulls(pos)) && \ | |
186 | ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); \ | |
187 | pos = rcu_dereference_raw(hlist_nulls_next_rcu(pos)); 1; });) | |
bbaffaca ED |
188 | #endif |
189 | #endif |