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git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - include/linux/rculist_nulls.h
1 #ifndef _LINUX_RCULIST_NULLS_H
2 #define _LINUX_RCULIST_NULLS_H
7 * RCU-protected list version
9 #include <linux/list_nulls.h>
10 #include <linux/rcupdate.h>
13 * hlist_nulls_del_init_rcu - deletes entry from hash list with re-initialization
14 * @n: the element to delete from the hash list.
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.
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
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().
32 static inline void hlist_nulls_del_init_rcu(struct hlist_nulls_node
*n
)
34 if (!hlist_nulls_unhashed(n
)) {
41 * hlist_nulls_del_rcu - deletes entry from hash list without re-initialization
42 * @n: the element to delete from the hash list.
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
48 * In particular, it means that we can not poison the forward
49 * pointers that may still be used for walking the hash list.
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().
59 static inline void hlist_nulls_del_rcu(struct hlist_nulls_node
*n
)
62 n
->pprev
= LIST_POISON2
;
66 * hlist_nulls_add_head_rcu
67 * @n: the element to add to the hash list.
68 * @h: the list to add to.
71 * Adds the specified element to the specified hlist_nulls,
72 * while permitting racing traversals.
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().
84 static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node
*n
,
85 struct hlist_nulls_head
*h
)
87 struct hlist_nulls_node
*first
= h
->first
;
91 rcu_assign_pointer(h
->first
, n
);
92 if (!is_a_nulls(first
))
93 first
->pprev
= &n
->next
;
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.
103 #define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \
104 for (pos = rcu_dereference_raw((head)->first); \
105 (!is_a_nulls(pos)) && \
106 ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \
107 pos = rcu_dereference_raw(pos->next))