| 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
| 2 | #ifndef _LINUX_LIST_BL_H |
| 3 | #define _LINUX_LIST_BL_H |
| 4 | |
| 5 | #include <linux/list.h> |
| 6 | #include <linux/bit_spinlock.h> |
| 7 | |
| 8 | /* |
| 9 | * Special version of lists, where head of the list has a lock in the lowest |
| 10 | * bit. This is useful for scalable hash tables without increasing memory |
| 11 | * footprint overhead. |
| 12 | * |
| 13 | * For modification operations, the 0 bit of hlist_bl_head->first |
| 14 | * pointer must be set. |
| 15 | * |
| 16 | * With some small modifications, this can easily be adapted to store several |
| 17 | * arbitrary bits (not just a single lock bit), if the need arises to store |
| 18 | * some fast and compact auxiliary data. |
| 19 | */ |
| 20 | |
| 21 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
| 22 | #define LIST_BL_LOCKMASK 1UL |
| 23 | #else |
| 24 | #define LIST_BL_LOCKMASK 0UL |
| 25 | #endif |
| 26 | |
| 27 | #ifdef CONFIG_DEBUG_LIST |
| 28 | #define LIST_BL_BUG_ON(x) BUG_ON(x) |
| 29 | #else |
| 30 | #define LIST_BL_BUG_ON(x) |
| 31 | #endif |
| 32 | |
| 33 | |
| 34 | struct hlist_bl_head { |
| 35 | struct hlist_bl_node *first; |
| 36 | }; |
| 37 | |
| 38 | struct hlist_bl_node { |
| 39 | struct hlist_bl_node *next, **pprev; |
| 40 | }; |
| 41 | #define INIT_HLIST_BL_HEAD(ptr) \ |
| 42 | ((ptr)->first = NULL) |
| 43 | |
| 44 | static inline void INIT_HLIST_BL_NODE(struct hlist_bl_node *h) |
| 45 | { |
| 46 | h->next = NULL; |
| 47 | h->pprev = NULL; |
| 48 | } |
| 49 | |
| 50 | #define hlist_bl_entry(ptr, type, member) container_of(ptr,type,member) |
| 51 | |
| 52 | static inline bool hlist_bl_unhashed(const struct hlist_bl_node *h) |
| 53 | { |
| 54 | return !h->pprev; |
| 55 | } |
| 56 | |
| 57 | static inline struct hlist_bl_node *hlist_bl_first(struct hlist_bl_head *h) |
| 58 | { |
| 59 | return (struct hlist_bl_node *) |
| 60 | ((unsigned long)h->first & ~LIST_BL_LOCKMASK); |
| 61 | } |
| 62 | |
| 63 | static inline void hlist_bl_set_first(struct hlist_bl_head *h, |
| 64 | struct hlist_bl_node *n) |
| 65 | { |
| 66 | LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK); |
| 67 | LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) != |
| 68 | LIST_BL_LOCKMASK); |
| 69 | h->first = (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK); |
| 70 | } |
| 71 | |
| 72 | static inline bool hlist_bl_empty(const struct hlist_bl_head *h) |
| 73 | { |
| 74 | return !((unsigned long)READ_ONCE(h->first) & ~LIST_BL_LOCKMASK); |
| 75 | } |
| 76 | |
| 77 | static inline void hlist_bl_add_head(struct hlist_bl_node *n, |
| 78 | struct hlist_bl_head *h) |
| 79 | { |
| 80 | struct hlist_bl_node *first = hlist_bl_first(h); |
| 81 | |
| 82 | n->next = first; |
| 83 | if (first) |
| 84 | first->pprev = &n->next; |
| 85 | n->pprev = &h->first; |
| 86 | hlist_bl_set_first(h, n); |
| 87 | } |
| 88 | |
| 89 | static inline void hlist_bl_add_before(struct hlist_bl_node *n, |
| 90 | struct hlist_bl_node *next) |
| 91 | { |
| 92 | struct hlist_bl_node **pprev = next->pprev; |
| 93 | |
| 94 | n->pprev = pprev; |
| 95 | n->next = next; |
| 96 | next->pprev = &n->next; |
| 97 | |
| 98 | /* pprev may be `first`, so be careful not to lose the lock bit */ |
| 99 | WRITE_ONCE(*pprev, |
| 100 | (struct hlist_bl_node *) |
| 101 | ((uintptr_t)n | ((uintptr_t)*pprev & LIST_BL_LOCKMASK))); |
| 102 | } |
| 103 | |
| 104 | static inline void hlist_bl_add_behind(struct hlist_bl_node *n, |
| 105 | struct hlist_bl_node *prev) |
| 106 | { |
| 107 | n->next = prev->next; |
| 108 | n->pprev = &prev->next; |
| 109 | prev->next = n; |
| 110 | |
| 111 | if (n->next) |
| 112 | n->next->pprev = &n->next; |
| 113 | } |
| 114 | |
| 115 | static inline void __hlist_bl_del(struct hlist_bl_node *n) |
| 116 | { |
| 117 | struct hlist_bl_node *next = n->next; |
| 118 | struct hlist_bl_node **pprev = n->pprev; |
| 119 | |
| 120 | LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK); |
| 121 | |
| 122 | /* pprev may be `first`, so be careful not to lose the lock bit */ |
| 123 | WRITE_ONCE(*pprev, |
| 124 | (struct hlist_bl_node *) |
| 125 | ((unsigned long)next | |
| 126 | ((unsigned long)*pprev & LIST_BL_LOCKMASK))); |
| 127 | if (next) |
| 128 | next->pprev = pprev; |
| 129 | } |
| 130 | |
| 131 | static inline void hlist_bl_del(struct hlist_bl_node *n) |
| 132 | { |
| 133 | __hlist_bl_del(n); |
| 134 | n->next = LIST_POISON1; |
| 135 | n->pprev = LIST_POISON2; |
| 136 | } |
| 137 | |
| 138 | static inline void hlist_bl_del_init(struct hlist_bl_node *n) |
| 139 | { |
| 140 | if (!hlist_bl_unhashed(n)) { |
| 141 | __hlist_bl_del(n); |
| 142 | INIT_HLIST_BL_NODE(n); |
| 143 | } |
| 144 | } |
| 145 | |
| 146 | static inline void hlist_bl_lock(struct hlist_bl_head *b) |
| 147 | { |
| 148 | bit_spin_lock(0, (unsigned long *)b); |
| 149 | } |
| 150 | |
| 151 | static inline void hlist_bl_unlock(struct hlist_bl_head *b) |
| 152 | { |
| 153 | __bit_spin_unlock(0, (unsigned long *)b); |
| 154 | } |
| 155 | |
| 156 | static inline bool hlist_bl_is_locked(struct hlist_bl_head *b) |
| 157 | { |
| 158 | return bit_spin_is_locked(0, (unsigned long *)b); |
| 159 | } |
| 160 | |
| 161 | /** |
| 162 | * hlist_bl_for_each_entry - iterate over list of given type |
| 163 | * @tpos: the type * to use as a loop cursor. |
| 164 | * @pos: the &struct hlist_node to use as a loop cursor. |
| 165 | * @head: the head for your list. |
| 166 | * @member: the name of the hlist_node within the struct. |
| 167 | * |
| 168 | */ |
| 169 | #define hlist_bl_for_each_entry(tpos, pos, head, member) \ |
| 170 | for (pos = hlist_bl_first(head); \ |
| 171 | pos && \ |
| 172 | ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \ |
| 173 | pos = pos->next) |
| 174 | |
| 175 | /** |
| 176 | * hlist_bl_for_each_entry_safe - iterate over list of given type safe against removal of list entry |
| 177 | * @tpos: the type * to use as a loop cursor. |
| 178 | * @pos: the &struct hlist_node to use as a loop cursor. |
| 179 | * @n: another &struct hlist_node to use as temporary storage |
| 180 | * @head: the head for your list. |
| 181 | * @member: the name of the hlist_node within the struct. |
| 182 | */ |
| 183 | #define hlist_bl_for_each_entry_safe(tpos, pos, n, head, member) \ |
| 184 | for (pos = hlist_bl_first(head); \ |
| 185 | pos && ({ n = pos->next; 1; }) && \ |
| 186 | ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \ |
| 187 | pos = n) |
| 188 | |
| 189 | #endif |