include/linux/list_bl.h

   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
  33 struct hlist_bl_head {
  34         struct hlist_bl_node *first;
  35 };
  36
  37 struct hlist_bl_node {
  38         struct hlist_bl_node *next, **pprev;
  39 };
  40 #define INIT_HLIST_BL_HEAD(ptr) \
  41         ((ptr)->first = NULL)
  42
  43 static 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
  51 static inline bool  hlist_bl_unhashed(const struct hlist_bl_node *h)
  52 {
  53         return !h->pprev;
  54 }
  55
  56 static 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
  62 static 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
  71 static inline bool hlist_bl_empty(const struct hlist_bl_head *h)
  72 {
  73         return !((unsigned long)READ_ONCE(h->first) & ~LIST_BL_LOCKMASK);
  74 }
  75
  76 static 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
  88 static 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         WRITE_ONCE(*pprev,
  97                    (struct hlist_bl_node *)
  98                         ((unsigned long)next |
  99                          ((unsigned long)*pprev & LIST_BL_LOCKMASK)));
 100         if (next)
 101                 next->pprev = pprev;
 102 }
 103
 104 static inline void hlist_bl_del(struct hlist_bl_node *n)
 105 {
 106         __hlist_bl_del(n);
 107         n->next = LIST_POISON1;
 108         n->pprev = LIST_POISON2;
 109 }
 110
 111 static inline void hlist_bl_del_init(struct hlist_bl_node *n)
 112 {
 113         if (!hlist_bl_unhashed(n)) {
 114                 __hlist_bl_del(n);
 115                 INIT_HLIST_BL_NODE(n);
 116         }
 117 }
 118
 119 static inline void hlist_bl_lock(struct hlist_bl_head *b)
 120 {
 121         bit_spin_lock(0, (unsigned long *)b);
 122 }
 123
 124 static inline void hlist_bl_unlock(struct hlist_bl_head *b)
 125 {
 126         __bit_spin_unlock(0, (unsigned long *)b);
 127 }
 128
 129 static inline bool hlist_bl_is_locked(struct hlist_bl_head *b)
 130 {
 131         return bit_spin_is_locked(0, (unsigned long *)b);
 132 }
 133
 134 /**
 135  * hlist_bl_for_each_entry      - iterate over list of given type
 136  * @tpos:       the type * to use as a loop cursor.
 137  * @pos:        the &struct hlist_node to use as a loop cursor.
 138  * @head:       the head for your list.
 139  * @member:     the name of the hlist_node within the struct.
 140  *
 141  */
 142 #define hlist_bl_for_each_entry(tpos, pos, head, member)                \
 143         for (pos = hlist_bl_first(head);                                \
 144              pos &&                                                     \
 145                 ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \
 146              pos = pos->next)
 147
 148 /**
 149  * hlist_bl_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 150  * @tpos:       the type * to use as a loop cursor.
 151  * @pos:        the &struct hlist_node to use as a loop cursor.
 152  * @n:          another &struct hlist_node to use as temporary storage
 153  * @head:       the head for your list.
 154  * @member:     the name of the hlist_node within the struct.
 155  */
 156 #define hlist_bl_for_each_entry_safe(tpos, pos, n, head, member)         \
 157         for (pos = hlist_bl_first(head);                                 \
 158              pos && ({ n = pos->next; 1; }) &&                           \
 159                 ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \
 160              pos = n)
 161
 162 #endif