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1 | #ifndef _LINUX_RCULIST_BL_H |
2 | #define _LINUX_RCULIST_BL_H |
3 | |
4 | /* |
5 | * RCU-protected bl list version. See include/linux/list_bl.h. |
6 | */ |
7 | #include <linux/list_bl.h> |
8 | #include <linux/rcupdate.h> |
9 | |
10 | static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h, |
11 | struct hlist_bl_node *n) |
12 | { |
13 | LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK); |
14 | LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) != |
15 | LIST_BL_LOCKMASK); |
16 | rcu_assign_pointer(h->first, |
17 | (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK)); |
18 | } |
19 | |
20 | static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h) |
21 | { |
22 | return (struct hlist_bl_node *) |
23 | ((unsigned long)rcu_dereference(h->first) & ~LIST_BL_LOCKMASK); |
24 | } |
25 | |
26 | /** |
27 | * hlist_bl_del_init_rcu - deletes entry from hash list with re-initialization |
28 | * @n: the element to delete from the hash list. |
29 | * |
30 | * Note: hlist_bl_unhashed() on the node returns true after this. It is |
31 | * useful for RCU based read lockfree traversal if the writer side |
32 | * must know if the list entry is still hashed or already unhashed. |
33 | * |
34 | * In particular, it means that we can not poison the forward pointers |
35 | * that may still be used for walking the hash list and we can only |
36 | * zero the pprev pointer so list_unhashed() will return true after |
37 | * this. |
38 | * |
39 | * The caller must take whatever precautions are necessary (such as |
40 | * holding appropriate locks) to avoid racing with another |
41 | * list-mutation primitive, such as hlist_bl_add_head_rcu() or |
42 | * hlist_bl_del_rcu(), running on this same list. However, it is |
43 | * perfectly legal to run concurrently with the _rcu list-traversal |
44 | * primitives, such as hlist_bl_for_each_entry_rcu(). |
45 | */ |
46 | static inline void hlist_bl_del_init_rcu(struct hlist_bl_node *n) |
47 | { |
48 | if (!hlist_bl_unhashed(n)) { |
49 | __hlist_bl_del(n); |
50 | n->pprev = NULL; |
51 | } |
52 | } |
53 | |
54 | /** |
55 | * hlist_bl_del_rcu - deletes entry from hash list without re-initialization |
56 | * @n: the element to delete from the hash list. |
57 | * |
58 | * Note: hlist_bl_unhashed() on entry does not return true after this, |
59 | * the entry is in an undefined state. It is useful for RCU based |
60 | * lockfree traversal. |
61 | * |
62 | * In particular, it means that we can not poison the forward |
63 | * pointers that may still be used for walking the hash list. |
64 | * |
65 | * The caller must take whatever precautions are necessary |
66 | * (such as holding appropriate locks) to avoid racing |
67 | * with another list-mutation primitive, such as hlist_bl_add_head_rcu() |
68 | * or hlist_bl_del_rcu(), running on this same list. |
69 | * However, it is perfectly legal to run concurrently with |
70 | * the _rcu list-traversal primitives, such as |
71 | * hlist_bl_for_each_entry(). |
72 | */ |
73 | static inline void hlist_bl_del_rcu(struct hlist_bl_node *n) |
74 | { |
75 | __hlist_bl_del(n); |
76 | n->pprev = LIST_POISON2; |
77 | } |
78 | |
79 | /** |
80 | * hlist_bl_add_head_rcu |
81 | * @n: the element to add to the hash list. |
82 | * @h: the list to add to. |
83 | * |
84 | * Description: |
85 | * Adds the specified element to the specified hlist_bl, |
86 | * while permitting racing traversals. |
87 | * |
88 | * The caller must take whatever precautions are necessary |
89 | * (such as holding appropriate locks) to avoid racing |
90 | * with another list-mutation primitive, such as hlist_bl_add_head_rcu() |
91 | * or hlist_bl_del_rcu(), running on this same list. |
92 | * However, it is perfectly legal to run concurrently with |
93 | * the _rcu list-traversal primitives, such as |
94 | * hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency |
95 | * problems on Alpha CPUs. Regardless of the type of CPU, the |
96 | * list-traversal primitive must be guarded by rcu_read_lock(). |
97 | */ |
98 | static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n, |
99 | struct hlist_bl_head *h) |
100 | { |
101 | struct hlist_bl_node *first; |
102 | |
103 | /* don't need hlist_bl_first_rcu because we're under lock */ |
104 | first = hlist_bl_first(h); |
105 | |
106 | n->next = first; |
107 | if (first) |
108 | first->pprev = &n->next; |
109 | n->pprev = &h->first; |
110 | |
111 | /* need _rcu because we can have concurrent lock free readers */ |
112 | hlist_bl_set_first_rcu(h, n); |
113 | } |
114 | /** |
115 | * hlist_bl_for_each_entry_rcu - iterate over rcu list of given type |
116 | * @tpos: the type * to use as a loop cursor. |
117 | * @pos: the &struct hlist_bl_node to use as a loop cursor. |
118 | * @head: the head for your list. |
119 | * @member: the name of the hlist_bl_node within the struct. |
120 | * |
121 | */ |
122 | #define hlist_bl_for_each_entry_rcu(tpos, pos, head, member) \ |
123 | for (pos = hlist_bl_first_rcu(head); \ |
124 | pos && \ |
125 | ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \ |
126 | pos = rcu_dereference_raw(pos->next)) |
127 | |
128 | #endif |
129 |
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