Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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/* return the first ptr or next element in an RCU protected list */
12#define hlist_bl_first_rcu(head) \
13 (*((struct hlist_bl_node __rcu **)(&(head)->first)))
14#define hlist_bl_next_rcu(node) \
15 (*((struct hlist_bl_node __rcu **)(&(node)->next)))
16
17static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
18 struct hlist_bl_node *n)
19{
20 LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
21 LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
22 LIST_BL_LOCKMASK);
23 rcu_assign_pointer(hlist_bl_first_rcu(h),
24 (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
25}
26
27#define hlist_bl_first_rcu_dereference(head) \
28({ \
29 struct hlist_bl_head *__head = (head); \
30 \
31 (struct hlist_bl_node *) \
32 ((unsigned long)rcu_dereference_check(hlist_bl_first_rcu(__head), \
33 hlist_bl_is_locked(__head)) & \
34 ~LIST_BL_LOCKMASK); \
35})
36
37/**
38 * hlist_bl_del_rcu - deletes entry from hash list without re-initialization
39 * @n: the element to delete from the hash list.
40 *
41 * Note: hlist_bl_unhashed() on entry does not return true after this,
42 * the entry is in an undefined state. It is useful for RCU based
43 * lockfree traversal.
44 *
45 * In particular, it means that we can not poison the forward
46 * pointers that may still be used for walking the hash list.
47 *
48 * The caller must take whatever precautions are necessary
49 * (such as holding appropriate locks) to avoid racing
50 * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
51 * or hlist_bl_del_rcu(), running on this same list.
52 * However, it is perfectly legal to run concurrently with
53 * the _rcu list-traversal primitives, such as
54 * hlist_bl_for_each_entry().
55 */
56static inline void hlist_bl_del_rcu(struct hlist_bl_node *n)
57{
58 __hlist_bl_del(n);
59 n->pprev = LIST_POISON2;
60}
61
62/**
63 * hlist_bl_add_head_rcu
64 * @n: the element to add to the hash list.
65 * @h: the list to add to.
66 *
67 * Description:
68 * Adds the specified element to the specified hlist_bl,
69 * while permitting racing traversals.
70 *
71 * The caller must take whatever precautions are necessary
72 * (such as holding appropriate locks) to avoid racing
73 * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
74 * or hlist_bl_del_rcu(), running on this same list.
75 * However, it is perfectly legal to run concurrently with
76 * the _rcu list-traversal primitives, such as
77 * hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency
78 * problems on Alpha CPUs. Regardless of the type of CPU, the
79 * list-traversal primitive must be guarded by rcu_read_lock().
80 */
81static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n,
82 struct hlist_bl_head *h)
83{
84 struct hlist_bl_node *first;
85
86 /* don't need hlist_bl_first_rcu* because we're under lock */
87 first = hlist_bl_first(h);
88
89 n->next = first;
90 if (first)
91 first->pprev = &n->next;
92 n->pprev = &h->first;
93
94 /* need _rcu because we can have concurrent lock free readers */
95 hlist_bl_set_first_rcu(h, n);
96}
97/**
98 * hlist_bl_for_each_entry_rcu - iterate over rcu list of given type
99 * @tpos: the type * to use as a loop cursor.
100 * @pos: the &struct hlist_bl_node to use as a loop cursor.
101 * @head: the head for your list.
102 * @member: the name of the hlist_bl_node within the struct.
103 *
104 */
105#define hlist_bl_for_each_entry_rcu(tpos, pos, head, member) \
106 for (pos = hlist_bl_first_rcu_dereference(head); \
107 pos && \
108 ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
109 pos = rcu_dereference_raw(hlist_bl_next_rcu(pos)))
110
111/**
112 * hlist_bl_for_each_entry_continue_rcu - continue iteration over list of given
113 * type
114 * @tpos: the type * to use as a loop cursor.
115 * @pos: the &struct hlist_bl_node to use as a loop cursor.
116 * @member: the name of the hlist_bl_node within the struct.
117 *
118 * Continue to iterate over list of given type, continuing after
119 * the current position which must have been in the list when the RCU read
120 * lock was taken.
121 * This would typically require either that you obtained the node from a
122 * previous walk of the list in the same RCU read-side critical section, or
123 * that you held some sort of non-RCU reference (such as a reference count)
124 * to keep the node alive *and* in the list.
125 */
126#define hlist_bl_for_each_entry_continue_rcu(tpos, pos, member) \
127 for (pos = rcu_dereference_raw(hlist_bl_next_rcu(&(tpos)->member)); \
128 pos && \
129 ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
130 pos = rcu_dereference_raw(hlist_bl_next_rcu(pos)))
131
132#endif