Line data Source code
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 :
40 : /**
41 : * hlist_nulls_del_rcu - deletes entry from hash list without re-initialization
42 : * @n: the element to delete from the hash list.
43 : *
44 : * Note: hlist_nulls_unhashed() on entry does not return true after this,
45 : * the entry is in an undefined state. It is useful for RCU based
46 : * lockfree traversal.
47 : *
48 : * In particular, it means that we can not poison the forward
49 : * pointers that may still be used for walking the hash list.
50 : *
51 : * The caller must take whatever precautions are necessary
52 : * (such as holding appropriate locks) to avoid racing
53 : * with another list-mutation primitive, such as hlist_nulls_add_head_rcu()
54 : * or hlist_nulls_del_rcu(), running on this same list.
55 : * However, it is perfectly legal to run concurrently with
56 : * the _rcu list-traversal primitives, such as
57 : * hlist_nulls_for_each_entry().
58 : */
59 : static inline void hlist_nulls_del_rcu(struct hlist_nulls_node *n)
60 : {
61 : __hlist_nulls_del(n);
62 : n->pprev = LIST_POISON2;
63 : }
64 :
65 : /**
66 : * hlist_nulls_add_head_rcu
67 : * @n: the element to add to the hash list.
68 : * @h: the list to add to.
69 : *
70 : * Description:
71 : * Adds the specified element to the specified hlist_nulls,
72 : * while permitting racing traversals.
73 : *
74 : * The caller must take whatever precautions are necessary
75 : * (such as holding appropriate locks) to avoid racing
76 : * with another list-mutation primitive, such as hlist_nulls_add_head_rcu()
77 : * or hlist_nulls_del_rcu(), running on this same list.
78 : * However, it is perfectly legal to run concurrently with
79 : * the _rcu list-traversal primitives, such as
80 : * hlist_nulls_for_each_entry_rcu(), used to prevent memory-consistency
81 : * problems on Alpha CPUs. Regardless of the type of CPU, the
82 : * list-traversal primitive must be guarded by rcu_read_lock().
83 : */
84 : static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n,
85 : struct hlist_nulls_head *h)
86 : {
87 : struct hlist_nulls_node *first = h->first;
88 :
89 : n->next = first;
90 : n->pprev = &h->first;
91 : rcu_assign_pointer(h->first, n);
92 : if (!is_a_nulls(first))
93 : first->pprev = &n->next;
94 : }
95 1 : /**
96 : * hlist_nulls_for_each_entry_rcu - iterate over rcu list of given type
97 : * @tpos: the type * to use as a loop cursor.
98 : * @pos: the &struct hlist_nulls_node to use as a loop cursor.
99 : * @head: the head for your list.
100 : * @member: the name of the hlist_nulls_node within the struct.
101 : *
102 : */
103 : #define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \
104 : for (pos = rcu_dereference((head)->first); \
105 : (!is_a_nulls(pos)) && \
106 : ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \
107 : pos = rcu_dereference(pos->next))
108 :
109 : #endif
110 : #endif
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