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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 | /** |
41 | * hlist_nulls_del_rcu - deletes entry from hash list without re-initialization |
42 | * @n: the element to delete from the hash list. |
43 | * |
44 | * Note: hlist_nulls_unhashed() on entry does not return true after this, |
45 | * the entry is in an undefined state. It is useful for RCU based |
46 | * lockfree traversal. |
47 | * |
48 | * In particular, it means that we can not poison the forward |
49 | * pointers that may still be used for walking the hash list. |
50 | * |
51 | * The caller must take whatever precautions are necessary |
52 | * (such as holding appropriate locks) to avoid racing |
53 | * with another list-mutation primitive, such as hlist_nulls_add_head_rcu() |
54 | * or hlist_nulls_del_rcu(), running on this same list. |
55 | * However, it is perfectly legal to run concurrently with |
56 | * the _rcu list-traversal primitives, such as |
57 | * hlist_nulls_for_each_entry(). |
58 | */ |
59 | static inline void hlist_nulls_del_rcu(struct hlist_nulls_node *n) |
60 | { |
61 | __hlist_nulls_del(n); |
62 | n->pprev = LIST_POISON2; |
63 | } |
64 | |
65 | /** |
66 | * hlist_nulls_add_head_rcu |
67 | * @n: the element to add to the hash list. |
68 | * @h: the list to add to. |
69 | * |
70 | * Description: |
71 | * Adds the specified element to the specified hlist_nulls, |
72 | * while permitting racing traversals. |
73 | * |
74 | * The caller must take whatever precautions are necessary |
75 | * (such as holding appropriate locks) to avoid racing |
76 | * with another list-mutation primitive, such as hlist_nulls_add_head_rcu() |
77 | * or hlist_nulls_del_rcu(), running on this same list. |
78 | * However, it is perfectly legal to run concurrently with |
79 | * the _rcu list-traversal primitives, such as |
80 | * hlist_nulls_for_each_entry_rcu(), used to prevent memory-consistency |
81 | * problems on Alpha CPUs. Regardless of the type of CPU, the |
82 | * list-traversal primitive must be guarded by rcu_read_lock(). |
83 | */ |
84 | static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n, |
85 | struct hlist_nulls_head *h) |
86 | { |
87 | struct hlist_nulls_node *first = h->first; |
88 | |
89 | n->next = first; |
90 | n->pprev = &h->first; |
91 | rcu_assign_pointer(h->first, n); |
92 | if (!is_a_nulls(first)) |
93 | first->pprev = &n->next; |
94 | } |
95 | /** |
96 | * hlist_nulls_for_each_entry_rcu - iterate over rcu list of given type |
97 | * @tpos: the type * to use as a loop cursor. |
98 | * @pos: the &struct hlist_nulls_node to use as a loop cursor. |
99 | * @head: the head for your list. |
100 | * @member: the name of the hlist_nulls_node within the struct. |
101 | * |
102 | */ |
103 | #define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \ |
104 | for (pos = rcu_dereference_raw((head)->first); \ |
105 | (!is_a_nulls(pos)) && \ |
106 | ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \ |
107 | pos = rcu_dereference_raw(pos->next)) |
108 | |
109 | #endif |
110 | #endif |
111 |
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