1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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); |
15 | LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) != |
16 | LIST_BL_LOCKMASK); |
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 *) |
24 | ((unsigned long)rcu_dereference_check(h->first, hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK); |
25 | } |
26 | |
27 | /** |
28 | * hlist_bl_del_rcu - deletes entry from hash list without re-initialization |
29 | * @n: the element to delete from the hash list. |
30 | * |
31 | * Note: hlist_bl_unhashed() on entry does not return true after this, |
32 | * the entry is in an undefined state. It is useful for RCU based |
33 | * lockfree traversal. |
34 | * |
35 | * In particular, it means that we can not poison the forward |
36 | * pointers that may still be used for walking the hash list. |
37 | * |
38 | * The caller must take whatever precautions are necessary |
39 | * (such as holding appropriate locks) to avoid racing |
40 | * with another list-mutation primitive, such as hlist_bl_add_head_rcu() |
41 | * or hlist_bl_del_rcu(), running on this same list. |
42 | * However, it is perfectly legal to run concurrently with |
43 | * the _rcu list-traversal primitives, such as |
44 | * hlist_bl_for_each_entry(). |
45 | */ |
46 | static inline void hlist_bl_del_rcu(struct hlist_bl_node *n) |
47 | { |
48 | __hlist_bl_del(n); |
49 | n->pprev = LIST_POISON2; |
50 | } |
51 | |
52 | /** |
53 | * hlist_bl_add_head_rcu |
54 | * @n: the element to add to the hash list. |
55 | * @h: the list to add to. |
56 | * |
57 | * Description: |
58 | * Adds the specified element to the specified hlist_bl, |
59 | * while permitting racing traversals. |
60 | * |
61 | * The caller must take whatever precautions are necessary |
62 | * (such as holding appropriate locks) to avoid racing |
63 | * with another list-mutation primitive, such as hlist_bl_add_head_rcu() |
64 | * or hlist_bl_del_rcu(), running on this same list. |
65 | * However, it is perfectly legal to run concurrently with |
66 | * the _rcu list-traversal primitives, such as |
67 | * hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency |
68 | * problems on Alpha CPUs. Regardless of the type of CPU, the |
69 | * list-traversal primitive must be guarded by rcu_read_lock(). |
70 | */ |
71 | static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n, |
72 | struct hlist_bl_head *h) |
73 | { |
74 | struct hlist_bl_node *first; |
75 | |
76 | /* don't need hlist_bl_first_rcu because we're under lock */ |
77 | first = hlist_bl_first(h); |
78 | |
79 | n->next = first; |
80 | if (first) |
81 | first->pprev = &n->next; |
82 | n->pprev = &h->first; |
83 | |
84 | /* need _rcu because we can have concurrent lock free readers */ |
85 | hlist_bl_set_first_rcu(h, n); |
86 | } |
87 | /** |
88 | * hlist_bl_for_each_entry_rcu - iterate over rcu list of given type |
89 | * @tpos: the type * to use as a loop cursor. |
90 | * @pos: the &struct hlist_bl_node to use as a loop cursor. |
91 | * @head: the head for your list. |
92 | * @member: the name of the hlist_bl_node within the struct. |
93 | * |
94 | */ |
95 | #define hlist_bl_for_each_entry_rcu(tpos, pos, head, member) \ |
96 | for (pos = hlist_bl_first_rcu(head); \ |
97 | pos && \ |
98 | ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \ |
99 | pos = rcu_dereference_raw(pos->next)) |
100 | |
101 | #endif |
102 | |