include/linux/list_bl.h

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