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Michel Lespinasse
4c199a93a2
Empty nodes have no color. We can make use of this property to simplify the code emitted by the RB_EMPTY_NODE and RB_CLEAR_NODE macros. Also, we can get rid of the rb_init_node function which had been introduced by commit88d19cf379("timers: Add rb_init_node() to allow for stack allocated rb nodes") to avoid some issue with the empty node's color not being initialized. I'm not sure what the RB_EMPTY_NODE checks in rb_prev() / rb_next() are doing there, though. axboe introduced them in commit10fd48f237("rbtree: fixed reversed RB_EMPTY_NODE and rb_next/prev"). The way I see it, the 'empty node' abstraction is only used by rbtree users to flag nodes that they haven't inserted in any rbtree, so asking the predecessor or successor of such nodes doesn't make any sense. One final rb_init_node() caller was recently added in sysctl code to implement faster sysctl name lookups. This code doesn't make use of RB_EMPTY_NODE at all, and from what I could see it only called rb_init_node() under the mistaken assumption that such initialization was required before node insertion. [sfr@canb.auug.org.au: fix net/ceph/osd_client.c build] Signed-off-by: Michel Lespinasse <walken@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Acked-by: David Woodhouse <David.Woodhouse@intel.com> Cc: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Daniel Santos <daniel.santos@pobox.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: John Stultz <john.stultz@linaro.org> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
108 lines
3.6 KiB
C
108 lines
3.6 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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struct rb_node
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{
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unsigned long rb_parent_color;
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#define RB_RED 0
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#define RB_BLACK 1
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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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{
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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_color(r) ((r)->rb_parent_color & 1)
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#define rb_is_red(r) (!rb_color(r))
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#define rb_is_black(r) rb_color(r)
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#define rb_set_red(r) do { (r)->rb_parent_color &= ~1; } while (0)
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#define rb_set_black(r) do { (r)->rb_parent_color |= 1; } while (0)
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static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
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{
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rb->rb_parent_color = (rb->rb_parent_color & 3) | (unsigned long)p;
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}
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static inline void rb_set_color(struct rb_node *rb, int color)
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{
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rb->rb_parent_color = (rb->rb_parent_color & ~1) | color;
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}
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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) ((root)->rb_node == NULL)
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/* 'empty' nodes are nodes that are known not to be inserted in an rbree */
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#define RB_EMPTY_NODE(node) ((node)->rb_parent_color == (unsigned long)(node))
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#define RB_CLEAR_NODE(node) ((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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typedef void (*rb_augment_f)(struct rb_node *node, void *data);
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extern void rb_augment_insert(struct rb_node *node,
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rb_augment_f func, void *data);
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extern struct rb_node *rb_augment_erase_begin(struct rb_node *node);
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extern void rb_augment_erase_end(struct rb_node *node,
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rb_augment_f func, void *data);
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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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/* 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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#endif /* _LINUX_RBTREE_H */
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