include/linux/rbtree.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3   Red Black Trees
   4   (C) 1999  Andrea Arcangeli <andrea@suse.de>
   5
   6
   7   linux/include/linux/rbtree.h
   8
   9   To use rbtrees you'll have to implement your own insert and search cores.
  10   This will avoid us to use callbacks and to drop drammatically performances.
  11   I know it's not the cleaner way,  but in C (not in C++) to get
  12   performances and genericity...
  13
  14   See Documentation/rbtree.txt for documentation and samples.
  15 */
  16
  17 #ifndef _LINUX_RBTREE_H
  18 #define _LINUX_RBTREE_H
  19
  20 #include <linux/kernel.h>
  21 #include <linux/stddef.h>
  22 #include <linux/rcupdate.h>
  23
  24 struct rb_node {
  25         unsigned long  __rb_parent_color;
  26         struct rb_node *rb_right;
  27         struct rb_node *rb_left;
  28 } __attribute__((aligned(sizeof(long))));
  29     /* The alignment might seem pointless, but allegedly CRIS needs it */
  30
  31 struct rb_root {
  32         struct rb_node *rb_node;
  33 };
  34
  35 /*
  36  * Leftmost-cached rbtrees.
  37  *
  38  * We do not cache the rightmost node based on footprint
  39  * size vs number of potential users that could benefit
  40  * from O(1) rb_last(). Just not worth it, users that want
  41  * this feature can always implement the logic explicitly.
  42  * Furthermore, users that want to cache both pointers may
  43  * find it a bit asymmetric, but that's ok.
  44  */
  45 struct rb_root_cached {
  46         struct rb_root rb_root;
  47         struct rb_node *rb_leftmost;
  48 };
  49
  50 #define rb_parent(r)   ((struct rb_node *)((r)->__rb_parent_color & ~3))
  51
  52 #define RB_ROOT (struct rb_root) { NULL, }
  53 #define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }
  54 #define rb_entry(ptr, type, member) container_of(ptr, type, member)
  55
  56 #define RB_EMPTY_ROOT(root)  (READ_ONCE((root)->rb_node) == NULL)
  57
  58 /* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
  59 #define RB_EMPTY_NODE(node)  \
  60         ((node)->__rb_parent_color == (unsigned long)(node))
  61 #define RB_CLEAR_NODE(node)  \
  62         ((node)->__rb_parent_color = (unsigned long)(node))
  63
  64
  65 extern void rb_insert_color(struct rb_node *, struct rb_root *);
  66 extern void rb_erase(struct rb_node *, struct rb_root *);
  67
  68
  69 /* Find logical next and previous nodes in a tree */
  70 extern struct rb_node *rb_next(const struct rb_node *);
  71 extern struct rb_node *rb_prev(const struct rb_node *);
  72 extern struct rb_node *rb_first(const struct rb_root *);
  73 extern struct rb_node *rb_last(const struct rb_root *);
  74
  75 extern void rb_insert_color_cached(struct rb_node *,
  76                                    struct rb_root_cached *, bool);
  77 extern void rb_erase_cached(struct rb_node *node, struct rb_root_cached *);
  78 /* Same as rb_first(), but O(1) */
  79 #define rb_first_cached(root) (root)->rb_leftmost
  80
  81 /* Postorder iteration - always visit the parent after its children */
  82 extern struct rb_node *rb_first_postorder(const struct rb_root *);
  83 extern struct rb_node *rb_next_postorder(const struct rb_node *);
  84
  85 /* Fast replacement of a single node without remove/rebalance/add/rebalance */
  86 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
  87                             struct rb_root *root);
  88 extern void rb_replace_node_rcu(struct rb_node *victim, struct rb_node *new,
  89                                 struct rb_root *root);
  90 extern void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new,
  91                                    struct rb_root_cached *root);
  92
  93 static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
  94                                 struct rb_node **rb_link)
  95 {
  96         node->__rb_parent_color = (unsigned long)parent;
  97         node->rb_left = node->rb_right = NULL;
  98
  99         *rb_link = node;
 100 }
 101
 102 static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
 103                                     struct rb_node **rb_link)
 104 {
 105         node->__rb_parent_color = (unsigned long)parent;
 106         node->rb_left = node->rb_right = NULL;
 107
 108         rcu_assign_pointer(*rb_link, node);
 109 }
 110
 111 #define rb_entry_safe(ptr, type, member) \
 112         ({ typeof(ptr) ____ptr = (ptr); \
 113            ____ptr ? rb_entry(____ptr, type, member) : NULL; \
 114         })
 115
 116 /**
 117  * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
 118  * given type allowing the backing memory of @pos to be invalidated
 119  *
 120  * @pos:        the 'type *' to use as a loop cursor.
 121  * @n:          another 'type *' to use as temporary storage
 122  * @root:       'rb_root *' of the rbtree.
 123  * @field:      the name of the rb_node field within 'type'.
 124  *
 125  * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
 126  * list_for_each_entry_safe() and allows the iteration to continue independent
 127  * of changes to @pos by the body of the loop.
 128  *
 129  * Note, however, that it cannot handle other modifications that re-order the
 130  * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
 131  * rb_erase() may rebalance the tree, causing us to miss some nodes.
 132  */
 133 #define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
 134         for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
 135              pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
 136                         typeof(*pos), field); 1; }); \
 137              pos = n)
 138
 139 #endif  /* _LINUX_RBTREE_H */