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bbaffaca ED |
1 | #ifndef _LINUX_LIST_NULLS_H |
2 | #define _LINUX_LIST_NULLS_H | |
3 | ||
a3449ded YX |
4 | #include <linux/poison.h> |
5 | #include <linux/const.h> | |
6 | ||
bbaffaca ED |
7 | /* |
8 | * Special version of lists, where end of list is not a NULL pointer, | |
9 | * but a 'nulls' marker, which can have many different values. | |
10 | * (up to 2^31 different values guaranteed on all platforms) | |
11 | * | |
12 | * In the standard hlist, termination of a list is the NULL pointer. | |
13 | * In this special 'nulls' variant, we use the fact that objects stored in | |
14 | * a list are aligned on a word (4 or 8 bytes alignment). | |
15 | * We therefore use the last significant bit of 'ptr' : | |
16 | * Set to 1 : This is a 'nulls' end-of-list marker (ptr >> 1) | |
17 | * Set to 0 : This is a pointer to some object (ptr) | |
18 | */ | |
19 | ||
20 | struct hlist_nulls_head { | |
21 | struct hlist_nulls_node *first; | |
22 | }; | |
23 | ||
24 | struct hlist_nulls_node { | |
25 | struct hlist_nulls_node *next, **pprev; | |
26 | }; | |
f89bd6f8 | 27 | #define NULLS_MARKER(value) (1UL | (((long)value) << 1)) |
bbaffaca | 28 | #define INIT_HLIST_NULLS_HEAD(ptr, nulls) \ |
f89bd6f8 | 29 | ((ptr)->first = (struct hlist_nulls_node *) NULLS_MARKER(nulls)) |
bbaffaca ED |
30 | |
31 | #define hlist_nulls_entry(ptr, type, member) container_of(ptr,type,member) | |
4fe84359 AS |
32 | |
33 | #define hlist_nulls_entry_safe(ptr, type, member) \ | |
34 | ({ typeof(ptr) ____ptr = (ptr); \ | |
35 | !is_a_nulls(____ptr) ? hlist_nulls_entry(____ptr, type, member) : NULL; \ | |
36 | }) | |
bbaffaca ED |
37 | /** |
38 | * ptr_is_a_nulls - Test if a ptr is a nulls | |
39 | * @ptr: ptr to be tested | |
40 | * | |
41 | */ | |
42 | static inline int is_a_nulls(const struct hlist_nulls_node *ptr) | |
43 | { | |
44 | return ((unsigned long)ptr & 1); | |
45 | } | |
46 | ||
47 | /** | |
48 | * get_nulls_value - Get the 'nulls' value of the end of chain | |
49 | * @ptr: end of chain | |
50 | * | |
51 | * Should be called only if is_a_nulls(ptr); | |
52 | */ | |
53 | static inline unsigned long get_nulls_value(const struct hlist_nulls_node *ptr) | |
54 | { | |
55 | return ((unsigned long)ptr) >> 1; | |
56 | } | |
57 | ||
58 | static inline int hlist_nulls_unhashed(const struct hlist_nulls_node *h) | |
59 | { | |
60 | return !h->pprev; | |
61 | } | |
62 | ||
63 | static inline int hlist_nulls_empty(const struct hlist_nulls_head *h) | |
64 | { | |
1658d35e | 65 | return is_a_nulls(READ_ONCE(h->first)); |
bbaffaca ED |
66 | } |
67 | ||
d219dce7 PNA |
68 | static inline void hlist_nulls_add_head(struct hlist_nulls_node *n, |
69 | struct hlist_nulls_head *h) | |
70 | { | |
71 | struct hlist_nulls_node *first = h->first; | |
72 | ||
73 | n->next = first; | |
74 | n->pprev = &h->first; | |
75 | h->first = n; | |
76 | if (!is_a_nulls(first)) | |
77 | first->pprev = &n->next; | |
78 | } | |
79 | ||
bbaffaca ED |
80 | static inline void __hlist_nulls_del(struct hlist_nulls_node *n) |
81 | { | |
82 | struct hlist_nulls_node *next = n->next; | |
83 | struct hlist_nulls_node **pprev = n->pprev; | |
7f5f873c PM |
84 | |
85 | WRITE_ONCE(*pprev, next); | |
bbaffaca ED |
86 | if (!is_a_nulls(next)) |
87 | next->pprev = pprev; | |
88 | } | |
89 | ||
d219dce7 PNA |
90 | static inline void hlist_nulls_del(struct hlist_nulls_node *n) |
91 | { | |
92 | __hlist_nulls_del(n); | |
93 | n->pprev = LIST_POISON2; | |
94 | } | |
95 | ||
bbaffaca ED |
96 | /** |
97 | * hlist_nulls_for_each_entry - iterate over list of given type | |
98 | * @tpos: the type * to use as a loop cursor. | |
99 | * @pos: the &struct hlist_node to use as a loop cursor. | |
100 | * @head: the head for your list. | |
101 | * @member: the name of the hlist_node within the struct. | |
102 | * | |
103 | */ | |
104 | #define hlist_nulls_for_each_entry(tpos, pos, head, member) \ | |
105 | for (pos = (head)->first; \ | |
106 | (!is_a_nulls(pos)) && \ | |
107 | ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1;}); \ | |
108 | pos = pos->next) | |
109 | ||
110 | /** | |
111 | * hlist_nulls_for_each_entry_from - iterate over a hlist continuing from current point | |
112 | * @tpos: the type * to use as a loop cursor. | |
113 | * @pos: the &struct hlist_node to use as a loop cursor. | |
114 | * @member: the name of the hlist_node within the struct. | |
115 | * | |
116 | */ | |
117 | #define hlist_nulls_for_each_entry_from(tpos, pos, member) \ | |
118 | for (; (!is_a_nulls(pos)) && \ | |
119 | ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1;}); \ | |
120 | pos = pos->next) | |
121 | ||
122 | #endif |