Commit | Line | Data |
---|---|---|
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); | |
37 | n->pprev = NULL; | |
38 | } | |
39 | } | |
40 | ||
67bdbffd AB |
41 | #define hlist_nulls_first_rcu(head) \ |
42 | (*((struct hlist_nulls_node __rcu __force **)&(head)->first)) | |
43 | ||
44 | #define hlist_nulls_next_rcu(node) \ | |
45 | (*((struct hlist_nulls_node __rcu __force **)&(node)->next)) | |
46 | ||
bbaffaca ED |
47 | /** |
48 | * hlist_nulls_del_rcu - deletes entry from hash list without re-initialization | |
49 | * @n: the element to delete from the hash list. | |
50 | * | |
51 | * Note: hlist_nulls_unhashed() on entry does not return true after this, | |
52 | * the entry is in an undefined state. It is useful for RCU based | |
53 | * lockfree traversal. | |
54 | * | |
55 | * In particular, it means that we can not poison the forward | |
56 | * pointers that may still be used for walking the hash list. | |
57 | * | |
58 | * The caller must take whatever precautions are necessary | |
59 | * (such as holding appropriate locks) to avoid racing | |
60 | * with another list-mutation primitive, such as hlist_nulls_add_head_rcu() | |
61 | * or hlist_nulls_del_rcu(), running on this same list. | |
62 | * However, it is perfectly legal to run concurrently with | |
63 | * the _rcu list-traversal primitives, such as | |
64 | * hlist_nulls_for_each_entry(). | |
65 | */ | |
66 | static inline void hlist_nulls_del_rcu(struct hlist_nulls_node *n) | |
67 | { | |
68 | __hlist_nulls_del(n); | |
69 | n->pprev = LIST_POISON2; | |
70 | } | |
71 | ||
72 | /** | |
73 | * hlist_nulls_add_head_rcu | |
74 | * @n: the element to add to the hash list. | |
75 | * @h: the list to add to. | |
76 | * | |
77 | * Description: | |
78 | * Adds the specified element to the specified hlist_nulls, | |
79 | * while permitting racing traversals. | |
80 | * | |
81 | * The caller must take whatever precautions are necessary | |
82 | * (such as holding appropriate locks) to avoid racing | |
83 | * with another list-mutation primitive, such as hlist_nulls_add_head_rcu() | |
84 | * or hlist_nulls_del_rcu(), running on this same list. | |
85 | * However, it is perfectly legal to run concurrently with | |
86 | * the _rcu list-traversal primitives, such as | |
87 | * hlist_nulls_for_each_entry_rcu(), used to prevent memory-consistency | |
88 | * problems on Alpha CPUs. Regardless of the type of CPU, the | |
89 | * list-traversal primitive must be guarded by rcu_read_lock(). | |
90 | */ | |
91 | static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n, | |
92 | struct hlist_nulls_head *h) | |
93 | { | |
94 | struct hlist_nulls_node *first = h->first; | |
95 | ||
96 | n->next = first; | |
97 | n->pprev = &h->first; | |
67bdbffd | 98 | rcu_assign_pointer(hlist_nulls_first_rcu(h), n); |
bbaffaca ED |
99 | if (!is_a_nulls(first)) |
100 | first->pprev = &n->next; | |
101 | } | |
d894ba18 | 102 | |
bbaffaca ED |
103 | /** |
104 | * hlist_nulls_for_each_entry_rcu - iterate over rcu list of given type | |
105 | * @tpos: the type * to use as a loop cursor. | |
106 | * @pos: the &struct hlist_nulls_node to use as a loop cursor. | |
107 | * @head: the head for your list. | |
108 | * @member: the name of the hlist_nulls_node within the struct. | |
109 | * | |
c87a124a ED |
110 | * The barrier() is needed to make sure compiler doesn't cache first element [1], |
111 | * as this loop can be restarted [2] | |
5fb94e9c | 112 | * [1] Documentation/core-api/atomic_ops.rst around line 114 |
c87a124a | 113 | * [2] Documentation/RCU/rculist_nulls.txt around line 146 |
bbaffaca | 114 | */ |
67bdbffd | 115 | #define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \ |
c87a124a ED |
116 | for (({barrier();}), \ |
117 | pos = rcu_dereference_raw(hlist_nulls_first_rcu(head)); \ | |
67bdbffd | 118 | (!is_a_nulls(pos)) && \ |
bbaffaca | 119 | ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \ |
67bdbffd | 120 | pos = rcu_dereference_raw(hlist_nulls_next_rcu(pos))) |
bbaffaca | 121 | |
4fe84359 AS |
122 | /** |
123 | * hlist_nulls_for_each_entry_safe - | |
124 | * iterate over list of given type safe against removal of list entry | |
125 | * @tpos: the type * to use as a loop cursor. | |
126 | * @pos: the &struct hlist_nulls_node to use as a loop cursor. | |
127 | * @head: the head for your list. | |
128 | * @member: the name of the hlist_nulls_node within the struct. | |
129 | */ | |
130 | #define hlist_nulls_for_each_entry_safe(tpos, pos, head, member) \ | |
131 | for (({barrier();}), \ | |
132 | pos = rcu_dereference_raw(hlist_nulls_first_rcu(head)); \ | |
133 | (!is_a_nulls(pos)) && \ | |
134 | ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); \ | |
135 | pos = rcu_dereference_raw(hlist_nulls_next_rcu(pos)); 1; });) | |
bbaffaca ED |
136 | #endif |
137 | #endif |