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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
4e35e607 NP |
2 | #ifndef _LINUX_RCULIST_BL_H |
3 | #define _LINUX_RCULIST_BL_H | |
4 | ||
5 | /* | |
6 | * RCU-protected bl list version. See include/linux/list_bl.h. | |
7 | */ | |
8 | #include <linux/list_bl.h> | |
9 | #include <linux/rcupdate.h> | |
10 | ||
11 | static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h, | |
12 | struct hlist_bl_node *n) | |
13 | { | |
14 | LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK); | |
2c675598 NP |
15 | LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) != |
16 | LIST_BL_LOCKMASK); | |
4e35e607 NP |
17 | rcu_assign_pointer(h->first, |
18 | (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK)); | |
19 | } | |
20 | ||
21 | static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h) | |
22 | { | |
23 | return (struct hlist_bl_node *) | |
49d0de08 | 24 | ((unsigned long)rcu_dereference_check(h->first, hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK); |
4e35e607 NP |
25 | } |
26 | ||
27 | /** | |
28 | * hlist_bl_del_init_rcu - deletes entry from hash list with re-initialization | |
29 | * @n: the element to delete from the hash list. | |
30 | * | |
31 | * Note: hlist_bl_unhashed() on the node returns true after this. It is | |
32 | * useful for RCU based read lockfree traversal if the writer side | |
33 | * must know if the list entry is still hashed or already unhashed. | |
34 | * | |
35 | * In particular, it means that we can not poison the forward pointers | |
36 | * that may still be used for walking the hash list and we can only | |
37 | * zero the pprev pointer so list_unhashed() will return true after | |
38 | * this. | |
39 | * | |
40 | * The caller must take whatever precautions are necessary (such as | |
41 | * holding appropriate locks) to avoid racing with another | |
42 | * list-mutation primitive, such as hlist_bl_add_head_rcu() or | |
43 | * hlist_bl_del_rcu(), running on this same list. However, it is | |
44 | * perfectly legal to run concurrently with the _rcu list-traversal | |
45 | * primitives, such as hlist_bl_for_each_entry_rcu(). | |
46 | */ | |
47 | static inline void hlist_bl_del_init_rcu(struct hlist_bl_node *n) | |
48 | { | |
49 | if (!hlist_bl_unhashed(n)) { | |
50 | __hlist_bl_del(n); | |
51 | n->pprev = NULL; | |
52 | } | |
53 | } | |
54 | ||
55 | /** | |
56 | * hlist_bl_del_rcu - deletes entry from hash list without re-initialization | |
57 | * @n: the element to delete from the hash list. | |
58 | * | |
59 | * Note: hlist_bl_unhashed() on entry does not return true after this, | |
60 | * the entry is in an undefined state. It is useful for RCU based | |
61 | * lockfree traversal. | |
62 | * | |
63 | * In particular, it means that we can not poison the forward | |
64 | * pointers that may still be used for walking the hash list. | |
65 | * | |
66 | * The caller must take whatever precautions are necessary | |
67 | * (such as holding appropriate locks) to avoid racing | |
68 | * with another list-mutation primitive, such as hlist_bl_add_head_rcu() | |
69 | * or hlist_bl_del_rcu(), running on this same list. | |
70 | * However, it is perfectly legal to run concurrently with | |
71 | * the _rcu list-traversal primitives, such as | |
72 | * hlist_bl_for_each_entry(). | |
73 | */ | |
74 | static inline void hlist_bl_del_rcu(struct hlist_bl_node *n) | |
75 | { | |
76 | __hlist_bl_del(n); | |
77 | n->pprev = LIST_POISON2; | |
78 | } | |
79 | ||
80 | /** | |
81 | * hlist_bl_add_head_rcu | |
82 | * @n: the element to add to the hash list. | |
83 | * @h: the list to add to. | |
84 | * | |
85 | * Description: | |
86 | * Adds the specified element to the specified hlist_bl, | |
87 | * while permitting racing traversals. | |
88 | * | |
89 | * The caller must take whatever precautions are necessary | |
90 | * (such as holding appropriate locks) to avoid racing | |
91 | * with another list-mutation primitive, such as hlist_bl_add_head_rcu() | |
92 | * or hlist_bl_del_rcu(), running on this same list. | |
93 | * However, it is perfectly legal to run concurrently with | |
94 | * the _rcu list-traversal primitives, such as | |
95 | * hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency | |
96 | * problems on Alpha CPUs. Regardless of the type of CPU, the | |
97 | * list-traversal primitive must be guarded by rcu_read_lock(). | |
98 | */ | |
99 | static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n, | |
100 | struct hlist_bl_head *h) | |
101 | { | |
102 | struct hlist_bl_node *first; | |
103 | ||
104 | /* don't need hlist_bl_first_rcu because we're under lock */ | |
105 | first = hlist_bl_first(h); | |
106 | ||
107 | n->next = first; | |
108 | if (first) | |
109 | first->pprev = &n->next; | |
110 | n->pprev = &h->first; | |
111 | ||
112 | /* need _rcu because we can have concurrent lock free readers */ | |
113 | hlist_bl_set_first_rcu(h, n); | |
114 | } | |
115 | /** | |
116 | * hlist_bl_for_each_entry_rcu - iterate over rcu list of given type | |
117 | * @tpos: the type * to use as a loop cursor. | |
118 | * @pos: the &struct hlist_bl_node to use as a loop cursor. | |
119 | * @head: the head for your list. | |
120 | * @member: the name of the hlist_bl_node within the struct. | |
121 | * | |
122 | */ | |
123 | #define hlist_bl_for_each_entry_rcu(tpos, pos, head, member) \ | |
124 | for (pos = hlist_bl_first_rcu(head); \ | |
125 | pos && \ | |
126 | ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \ | |
127 | pos = rcu_dereference_raw(pos->next)) | |
128 | ||
129 | #endif |