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bbaffaca ED |
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 | ||
67bdbffd AB |
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 | ||
bbaffaca ED |
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; | |
67bdbffd | 97 | rcu_assign_pointer(hlist_nulls_first_rcu(h), n); |
bbaffaca ED |
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 | * | |
c87a124a ED |
108 | * The barrier() is needed to make sure compiler doesn't cache first element [1], |
109 | * as this loop can be restarted [2] | |
110 | * [1] Documentation/atomic_ops.txt around line 114 | |
111 | * [2] Documentation/RCU/rculist_nulls.txt around line 146 | |
bbaffaca | 112 | */ |
67bdbffd | 113 | #define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \ |
c87a124a ED |
114 | for (({barrier();}), \ |
115 | pos = rcu_dereference_raw(hlist_nulls_first_rcu(head)); \ | |
67bdbffd | 116 | (!is_a_nulls(pos)) && \ |
bbaffaca | 117 | ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \ |
67bdbffd | 118 | pos = rcu_dereference_raw(hlist_nulls_next_rcu(pos))) |
bbaffaca ED |
119 | |
120 | #endif | |
121 | #endif |