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a460bece02
With commit d72da4a4d9 ("rbtree: Make lockless searches non-fatal") our
rbtrees provide weak guarantees that allows us to do lockless (and very
speculative) reads of the tree. Such readers cannot see partial stores
on nodes, ie left/right as well as root. As such, similar to the
WRITE_ONCE semantics when doing rotations, use READ_ONCE when checking
the root node in RB_EMPTY_ROOT.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
127 lines
4.4 KiB
C
127 lines
4.4 KiB
C
/*
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Red Black Trees
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(C) 1999 Andrea Arcangeli <andrea@suse.de>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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linux/include/linux/rbtree.h
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To use rbtrees you'll have to implement your own insert and search cores.
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This will avoid us to use callbacks and to drop drammatically performances.
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I know it's not the cleaner way, but in C (not in C++) to get
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performances and genericity...
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See Documentation/rbtree.txt for documentation and samples.
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*/
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#ifndef _LINUX_RBTREE_H
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#define _LINUX_RBTREE_H
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#include <linux/kernel.h>
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#include <linux/stddef.h>
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#include <linux/rcupdate.h>
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struct rb_node {
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unsigned long __rb_parent_color;
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struct rb_node *rb_right;
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struct rb_node *rb_left;
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} __attribute__((aligned(sizeof(long))));
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/* The alignment might seem pointless, but allegedly CRIS needs it */
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struct rb_root {
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struct rb_node *rb_node;
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};
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#define rb_parent(r) ((struct rb_node *)((r)->__rb_parent_color & ~3))
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#define RB_ROOT (struct rb_root) { NULL, }
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#define rb_entry(ptr, type, member) container_of(ptr, type, member)
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#define RB_EMPTY_ROOT(root) (READ_ONCE((root)->rb_node) == NULL)
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/* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
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#define RB_EMPTY_NODE(node) \
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((node)->__rb_parent_color == (unsigned long)(node))
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#define RB_CLEAR_NODE(node) \
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((node)->__rb_parent_color = (unsigned long)(node))
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extern void rb_insert_color(struct rb_node *, struct rb_root *);
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extern void rb_erase(struct rb_node *, struct rb_root *);
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/* Find logical next and previous nodes in a tree */
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extern struct rb_node *rb_next(const struct rb_node *);
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extern struct rb_node *rb_prev(const struct rb_node *);
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extern struct rb_node *rb_first(const struct rb_root *);
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extern struct rb_node *rb_last(const struct rb_root *);
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/* Postorder iteration - always visit the parent after its children */
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extern struct rb_node *rb_first_postorder(const struct rb_root *);
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extern struct rb_node *rb_next_postorder(const struct rb_node *);
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/* Fast replacement of a single node without remove/rebalance/add/rebalance */
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extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
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struct rb_root *root);
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static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
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struct rb_node **rb_link)
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{
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node->__rb_parent_color = (unsigned long)parent;
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node->rb_left = node->rb_right = NULL;
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*rb_link = node;
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}
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static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
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struct rb_node **rb_link)
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{
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node->__rb_parent_color = (unsigned long)parent;
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node->rb_left = node->rb_right = NULL;
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rcu_assign_pointer(*rb_link, node);
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}
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#define rb_entry_safe(ptr, type, member) \
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({ typeof(ptr) ____ptr = (ptr); \
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____ptr ? rb_entry(____ptr, type, member) : NULL; \
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})
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/**
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* rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
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* given type allowing the backing memory of @pos to be invalidated
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*
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* @pos: the 'type *' to use as a loop cursor.
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* @n: another 'type *' to use as temporary storage
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* @root: 'rb_root *' of the rbtree.
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* @field: the name of the rb_node field within 'type'.
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*
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* rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
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* list_for_each_entry_safe() and allows the iteration to continue independent
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* of changes to @pos by the body of the loop.
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*
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* Note, however, that it cannot handle other modifications that re-order the
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* rbtree it is iterating over. This includes calling rb_erase() on @pos, as
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* rb_erase() may rebalance the tree, causing us to miss some nodes.
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*/
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#define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
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for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
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pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
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typeof(*pos), field); 1; }); \
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pos = n)
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#endif /* _LINUX_RBTREE_H */
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