]>
git.proxmox.com Git - mirror_ubuntu-eoan-kernel.git/blob - include/linux/rculist_nulls.h
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_RCULIST_NULLS_H
3 #define _LINUX_RCULIST_NULLS_H
8 * RCU-protected list version
10 #include <linux/list_nulls.h>
11 #include <linux/rcupdate.h>
14 * hlist_nulls_del_init_rcu - deletes entry from hash list with re-initialization
15 * @n: the element to delete from the hash list.
17 * Note: hlist_nulls_unhashed() on the node return true after this. It is
18 * useful for RCU based read lockfree traversal if the writer side
19 * must know if the list entry is still hashed or already unhashed.
21 * In particular, it means that we can not poison the forward pointers
22 * that may still be used for walking the hash list and we can only
23 * zero the pprev pointer so list_unhashed() will return true after
26 * The caller must take whatever precautions are necessary (such as
27 * holding appropriate locks) to avoid racing with another
28 * list-mutation primitive, such as hlist_nulls_add_head_rcu() or
29 * hlist_nulls_del_rcu(), running on this same list. However, it is
30 * perfectly legal to run concurrently with the _rcu list-traversal
31 * primitives, such as hlist_nulls_for_each_entry_rcu().
33 static inline void hlist_nulls_del_init_rcu(struct hlist_nulls_node
*n
)
35 if (!hlist_nulls_unhashed(n
)) {
41 #define hlist_nulls_first_rcu(head) \
42 (*((struct hlist_nulls_node __rcu __force **)&(head)->first))
44 #define hlist_nulls_next_rcu(node) \
45 (*((struct hlist_nulls_node __rcu __force **)&(node)->next))
48 * hlist_nulls_del_rcu - deletes entry from hash list without re-initialization
49 * @n: the element to delete from the hash list.
51 * Note: hlist_nulls_unhashed() on entry does not return true after this,
52 * the entry is in an undefined state. It is useful for RCU based
55 * In particular, it means that we can not poison the forward
56 * pointers that may still be used for walking the hash list.
58 * The caller must take whatever precautions are necessary
59 * (such as holding appropriate locks) to avoid racing
60 * with another list-mutation primitive, such as hlist_nulls_add_head_rcu()
61 * or hlist_nulls_del_rcu(), running on this same list.
62 * However, it is perfectly legal to run concurrently with
63 * the _rcu list-traversal primitives, such as
64 * hlist_nulls_for_each_entry().
66 static inline void hlist_nulls_del_rcu(struct hlist_nulls_node
*n
)
69 n
->pprev
= LIST_POISON2
;
73 * hlist_nulls_add_head_rcu
74 * @n: the element to add to the hash list.
75 * @h: the list to add to.
78 * Adds the specified element to the specified hlist_nulls,
79 * while permitting racing traversals.
81 * The caller must take whatever precautions are necessary
82 * (such as holding appropriate locks) to avoid racing
83 * with another list-mutation primitive, such as hlist_nulls_add_head_rcu()
84 * or hlist_nulls_del_rcu(), running on this same list.
85 * However, it is perfectly legal to run concurrently with
86 * the _rcu list-traversal primitives, such as
87 * hlist_nulls_for_each_entry_rcu(), used to prevent memory-consistency
88 * problems on Alpha CPUs. Regardless of the type of CPU, the
89 * list-traversal primitive must be guarded by rcu_read_lock().
91 static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node
*n
,
92 struct hlist_nulls_head
*h
)
94 struct hlist_nulls_node
*first
= h
->first
;
98 rcu_assign_pointer(hlist_nulls_first_rcu(h
), n
);
99 if (!is_a_nulls(first
))
100 first
->pprev
= &n
->next
;
104 * hlist_nulls_for_each_entry_rcu - iterate over rcu list of given type
105 * @tpos: the type * to use as a loop cursor.
106 * @pos: the &struct hlist_nulls_node to use as a loop cursor.
107 * @head: the head for your list.
108 * @member: the name of the hlist_nulls_node within the struct.
110 * The barrier() is needed to make sure compiler doesn't cache first element [1],
111 * as this loop can be restarted [2]
112 * [1] Documentation/core-api/atomic_ops.rst around line 114
113 * [2] Documentation/RCU/rculist_nulls.txt around line 146
115 #define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \
116 for (({barrier();}), \
117 pos = rcu_dereference_raw(hlist_nulls_first_rcu(head)); \
118 (!is_a_nulls(pos)) && \
119 ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \
120 pos = rcu_dereference_raw(hlist_nulls_next_rcu(pos)))
123 * hlist_nulls_for_each_entry_safe -
124 * iterate over list of given type safe against removal of list entry
125 * @tpos: the type * to use as a loop cursor.
126 * @pos: the &struct hlist_nulls_node to use as a loop cursor.
127 * @head: the head for your list.
128 * @member: the name of the hlist_nulls_node within the struct.
130 #define hlist_nulls_for_each_entry_safe(tpos, pos, head, member) \
131 for (({barrier();}), \
132 pos = rcu_dereference_raw(hlist_nulls_first_rcu(head)); \
133 (!is_a_nulls(pos)) && \
134 ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); \
135 pos = rcu_dereference_raw(hlist_nulls_next_rcu(pos)); 1; });)