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