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4e35e607 NP |
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 | rcu_assign_pointer(h->first, | |
16 | (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK)); | |
17 | } | |
18 | ||
19 | static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h) | |
20 | { | |
21 | return (struct hlist_bl_node *) | |
22 | ((unsigned long)rcu_dereference(h->first) & ~LIST_BL_LOCKMASK); | |
23 | } | |
24 | ||
25 | /** | |
26 | * hlist_bl_del_init_rcu - deletes entry from hash list with re-initialization | |
27 | * @n: the element to delete from the hash list. | |
28 | * | |
29 | * Note: hlist_bl_unhashed() on the node returns true after this. It is | |
30 | * useful for RCU based read lockfree traversal if the writer side | |
31 | * must know if the list entry is still hashed or already unhashed. | |
32 | * | |
33 | * In particular, it means that we can not poison the forward pointers | |
34 | * that may still be used for walking the hash list and we can only | |
35 | * zero the pprev pointer so list_unhashed() will return true after | |
36 | * this. | |
37 | * | |
38 | * The caller must take whatever precautions are necessary (such as | |
39 | * holding appropriate locks) to avoid racing with another | |
40 | * list-mutation primitive, such as hlist_bl_add_head_rcu() or | |
41 | * hlist_bl_del_rcu(), running on this same list. However, it is | |
42 | * perfectly legal to run concurrently with the _rcu list-traversal | |
43 | * primitives, such as hlist_bl_for_each_entry_rcu(). | |
44 | */ | |
45 | static inline void hlist_bl_del_init_rcu(struct hlist_bl_node *n) | |
46 | { | |
47 | if (!hlist_bl_unhashed(n)) { | |
48 | __hlist_bl_del(n); | |
49 | n->pprev = NULL; | |
50 | } | |
51 | } | |
52 | ||
53 | /** | |
54 | * hlist_bl_del_rcu - deletes entry from hash list without re-initialization | |
55 | * @n: the element to delete from the hash list. | |
56 | * | |
57 | * Note: hlist_bl_unhashed() on entry does not return true after this, | |
58 | * the entry is in an undefined state. It is useful for RCU based | |
59 | * lockfree traversal. | |
60 | * | |
61 | * In particular, it means that we can not poison the forward | |
62 | * pointers that may still be used for walking the hash list. | |
63 | * | |
64 | * The caller must take whatever precautions are necessary | |
65 | * (such as holding appropriate locks) to avoid racing | |
66 | * with another list-mutation primitive, such as hlist_bl_add_head_rcu() | |
67 | * or hlist_bl_del_rcu(), running on this same list. | |
68 | * However, it is perfectly legal to run concurrently with | |
69 | * the _rcu list-traversal primitives, such as | |
70 | * hlist_bl_for_each_entry(). | |
71 | */ | |
72 | static inline void hlist_bl_del_rcu(struct hlist_bl_node *n) | |
73 | { | |
74 | __hlist_bl_del(n); | |
75 | n->pprev = LIST_POISON2; | |
76 | } | |
77 | ||
78 | /** | |
79 | * hlist_bl_add_head_rcu | |
80 | * @n: the element to add to the hash list. | |
81 | * @h: the list to add to. | |
82 | * | |
83 | * Description: | |
84 | * Adds the specified element to the specified hlist_bl, | |
85 | * while permitting racing traversals. | |
86 | * | |
87 | * The caller must take whatever precautions are necessary | |
88 | * (such as holding appropriate locks) to avoid racing | |
89 | * with another list-mutation primitive, such as hlist_bl_add_head_rcu() | |
90 | * or hlist_bl_del_rcu(), running on this same list. | |
91 | * However, it is perfectly legal to run concurrently with | |
92 | * the _rcu list-traversal primitives, such as | |
93 | * hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency | |
94 | * problems on Alpha CPUs. Regardless of the type of CPU, the | |
95 | * list-traversal primitive must be guarded by rcu_read_lock(). | |
96 | */ | |
97 | static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n, | |
98 | struct hlist_bl_head *h) | |
99 | { | |
100 | struct hlist_bl_node *first; | |
101 | ||
102 | /* don't need hlist_bl_first_rcu because we're under lock */ | |
103 | first = hlist_bl_first(h); | |
104 | ||
105 | n->next = first; | |
106 | if (first) | |
107 | first->pprev = &n->next; | |
108 | n->pprev = &h->first; | |
109 | ||
110 | /* need _rcu because we can have concurrent lock free readers */ | |
111 | hlist_bl_set_first_rcu(h, n); | |
112 | } | |
113 | /** | |
114 | * hlist_bl_for_each_entry_rcu - iterate over rcu list of given type | |
115 | * @tpos: the type * to use as a loop cursor. | |
116 | * @pos: the &struct hlist_bl_node to use as a loop cursor. | |
117 | * @head: the head for your list. | |
118 | * @member: the name of the hlist_bl_node within the struct. | |
119 | * | |
120 | */ | |
121 | #define hlist_bl_for_each_entry_rcu(tpos, pos, head, member) \ | |
122 | for (pos = hlist_bl_first_rcu(head); \ | |
123 | pos && \ | |
124 | ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \ | |
125 | pos = rcu_dereference_raw(pos->next)) | |
126 | ||
127 | #endif |