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1 | #ifndef _LINUX_RCULIST_NULLS_H |
2 | #define _LINUX_RCULIST_NULLS_H |
3 | |
4 | #ifdef __KERNEL__ |
5 | |
6 | /* |
7 | * RCU-protected list version |
8 | */ |
9 | #include <linux/list_nulls.h> |
10 | #include <linux/rcupdate.h> |
11 | |
12 | /** |
13 | * hlist_nulls_del_init_rcu - deletes entry from hash list with re-initialization |
14 | * @n: the element to delete from the hash list. |
15 | * |
16 | * Note: hlist_nulls_unhashed() on the node return true after this. It is |
17 | * useful for RCU based read lockfree traversal if the writer side |
18 | * must know if the list entry is still hashed or already unhashed. |
19 | * |
20 | * In particular, it means that we can not poison the forward pointers |
21 | * that may still be used for walking the hash list and we can only |
22 | * zero the pprev pointer so list_unhashed() will return true after |
23 | * this. |
24 | * |
25 | * The caller must take whatever precautions are necessary (such as |
26 | * holding appropriate locks) to avoid racing with another |
27 | * list-mutation primitive, such as hlist_nulls_add_head_rcu() or |
28 | * hlist_nulls_del_rcu(), running on this same list. However, it is |
29 | * perfectly legal to run concurrently with the _rcu list-traversal |
30 | * primitives, such as hlist_nulls_for_each_entry_rcu(). |
31 | */ |
32 | static inline void hlist_nulls_del_init_rcu(struct hlist_nulls_node *n) |
33 | { |
34 | if (!hlist_nulls_unhashed(n)) { |
35 | __hlist_nulls_del(n); |
36 | n->pprev = NULL; |
37 | } |
38 | } |
39 | |
40 | #define hlist_nulls_first_rcu(head) \ |
41 | (*((struct hlist_nulls_node __rcu __force **)&(head)->first)) |
42 | |
43 | #define hlist_nulls_next_rcu(node) \ |
44 | (*((struct hlist_nulls_node __rcu __force **)&(node)->next)) |
45 | |
46 | /** |
47 | * hlist_nulls_del_rcu - deletes entry from hash list without re-initialization |
48 | * @n: the element to delete from the hash list. |
49 | * |
50 | * Note: hlist_nulls_unhashed() on entry does not return true after this, |
51 | * the entry is in an undefined state. It is useful for RCU based |
52 | * lockfree traversal. |
53 | * |
54 | * In particular, it means that we can not poison the forward |
55 | * pointers that may still be used for walking the hash list. |
56 | * |
57 | * The caller must take whatever precautions are necessary |
58 | * (such as holding appropriate locks) to avoid racing |
59 | * with another list-mutation primitive, such as hlist_nulls_add_head_rcu() |
60 | * or hlist_nulls_del_rcu(), running on this same list. |
61 | * However, it is perfectly legal to run concurrently with |
62 | * the _rcu list-traversal primitives, such as |
63 | * hlist_nulls_for_each_entry(). |
64 | */ |
65 | static inline void hlist_nulls_del_rcu(struct hlist_nulls_node *n) |
66 | { |
67 | __hlist_nulls_del(n); |
68 | n->pprev = LIST_POISON2; |
69 | } |
70 | |
71 | /** |
72 | * hlist_nulls_add_head_rcu |
73 | * @n: the element to add to the hash list. |
74 | * @h: the list to add to. |
75 | * |
76 | * Description: |
77 | * Adds the specified element to the specified hlist_nulls, |
78 | * while permitting racing traversals. |
79 | * |
80 | * The caller must take whatever precautions are necessary |
81 | * (such as holding appropriate locks) to avoid racing |
82 | * with another list-mutation primitive, such as hlist_nulls_add_head_rcu() |
83 | * or hlist_nulls_del_rcu(), running on this same list. |
84 | * However, it is perfectly legal to run concurrently with |
85 | * the _rcu list-traversal primitives, such as |
86 | * hlist_nulls_for_each_entry_rcu(), used to prevent memory-consistency |
87 | * problems on Alpha CPUs. Regardless of the type of CPU, the |
88 | * list-traversal primitive must be guarded by rcu_read_lock(). |
89 | */ |
90 | static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n, |
91 | struct hlist_nulls_head *h) |
92 | { |
93 | struct hlist_nulls_node *first = h->first; |
94 | |
95 | n->next = first; |
96 | n->pprev = &h->first; |
97 | rcu_assign_pointer(hlist_nulls_first_rcu(h), n); |
98 | if (!is_a_nulls(first)) |
99 | first->pprev = &n->next; |
100 | } |
101 | /** |
102 | * hlist_nulls_for_each_entry_rcu - iterate over rcu list of given type |
103 | * @tpos: the type * to use as a loop cursor. |
104 | * @pos: the &struct hlist_nulls_node to use as a loop cursor. |
105 | * @head: the head for your list. |
106 | * @member: the name of the hlist_nulls_node within the struct. |
107 | * |
108 | */ |
109 | #define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \ |
110 | for (pos = rcu_dereference_raw(hlist_nulls_first_rcu(head)); \ |
111 | (!is_a_nulls(pos)) && \ |
112 | ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \ |
113 | pos = rcu_dereference_raw(hlist_nulls_next_rcu(pos))) |
114 | |
115 | #endif |
116 | #endif |
117 |
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