forked from mirrors/linux
99d4d26551
While slightly sub-optimal, updating the augmented data while going down the tree during lookup would be faster -- alas the augment interface does not currently allow for that, provide a generic helper to add a node to an augmented cached tree. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20230531124603.862983648@infradead.org
343 lines
10 KiB
C
343 lines
10 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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Red Black Trees
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(C) 1999 Andrea Arcangeli <andrea@suse.de>
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(C) 2002 David Woodhouse <dwmw2@infradead.org>
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(C) 2012 Michel Lespinasse <walken@google.com>
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linux/include/linux/rbtree_augmented.h
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*/
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#ifndef _LINUX_RBTREE_AUGMENTED_H
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#define _LINUX_RBTREE_AUGMENTED_H
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#include <linux/compiler.h>
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#include <linux/rbtree.h>
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#include <linux/rcupdate.h>
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/*
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* Please note - only struct rb_augment_callbacks and the prototypes for
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* rb_insert_augmented() and rb_erase_augmented() are intended to be public.
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* The rest are implementation details you are not expected to depend on.
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*
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* See Documentation/core-api/rbtree.rst for documentation and samples.
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*/
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struct rb_augment_callbacks {
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void (*propagate)(struct rb_node *node, struct rb_node *stop);
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void (*copy)(struct rb_node *old, struct rb_node *new);
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void (*rotate)(struct rb_node *old, struct rb_node *new);
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};
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extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
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void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
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/*
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* Fixup the rbtree and update the augmented information when rebalancing.
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*
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* On insertion, the user must update the augmented information on the path
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* leading to the inserted node, then call rb_link_node() as usual and
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* rb_insert_augmented() instead of the usual rb_insert_color() call.
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* If rb_insert_augmented() rebalances the rbtree, it will callback into
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* a user provided function to update the augmented information on the
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* affected subtrees.
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*/
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static inline void
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rb_insert_augmented(struct rb_node *node, struct rb_root *root,
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const struct rb_augment_callbacks *augment)
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{
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__rb_insert_augmented(node, root, augment->rotate);
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}
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static inline void
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rb_insert_augmented_cached(struct rb_node *node,
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struct rb_root_cached *root, bool newleft,
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const struct rb_augment_callbacks *augment)
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{
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if (newleft)
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root->rb_leftmost = node;
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rb_insert_augmented(node, &root->rb_root, augment);
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}
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static __always_inline struct rb_node *
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rb_add_augmented_cached(struct rb_node *node, struct rb_root_cached *tree,
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bool (*less)(struct rb_node *, const struct rb_node *),
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const struct rb_augment_callbacks *augment)
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{
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struct rb_node **link = &tree->rb_root.rb_node;
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struct rb_node *parent = NULL;
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bool leftmost = true;
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while (*link) {
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parent = *link;
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if (less(node, parent)) {
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link = &parent->rb_left;
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} else {
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link = &parent->rb_right;
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leftmost = false;
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}
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}
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rb_link_node(node, parent, link);
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augment->propagate(parent, NULL); /* suboptimal */
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rb_insert_augmented_cached(node, tree, leftmost, augment);
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return leftmost ? node : NULL;
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}
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/*
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* Template for declaring augmented rbtree callbacks (generic case)
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*
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* RBSTATIC: 'static' or empty
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* RBNAME: name of the rb_augment_callbacks structure
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* RBSTRUCT: struct type of the tree nodes
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* RBFIELD: name of struct rb_node field within RBSTRUCT
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* RBAUGMENTED: name of field within RBSTRUCT holding data for subtree
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* RBCOMPUTE: name of function that recomputes the RBAUGMENTED data
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*/
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#define RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME, \
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RBSTRUCT, RBFIELD, RBAUGMENTED, RBCOMPUTE) \
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static inline void \
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RBNAME ## _propagate(struct rb_node *rb, struct rb_node *stop) \
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{ \
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while (rb != stop) { \
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RBSTRUCT *node = rb_entry(rb, RBSTRUCT, RBFIELD); \
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if (RBCOMPUTE(node, true)) \
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break; \
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rb = rb_parent(&node->RBFIELD); \
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} \
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} \
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static inline void \
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RBNAME ## _copy(struct rb_node *rb_old, struct rb_node *rb_new) \
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{ \
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RBSTRUCT *old = rb_entry(rb_old, RBSTRUCT, RBFIELD); \
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RBSTRUCT *new = rb_entry(rb_new, RBSTRUCT, RBFIELD); \
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new->RBAUGMENTED = old->RBAUGMENTED; \
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} \
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static void \
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RBNAME ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new) \
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{ \
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RBSTRUCT *old = rb_entry(rb_old, RBSTRUCT, RBFIELD); \
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RBSTRUCT *new = rb_entry(rb_new, RBSTRUCT, RBFIELD); \
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new->RBAUGMENTED = old->RBAUGMENTED; \
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RBCOMPUTE(old, false); \
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} \
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RBSTATIC const struct rb_augment_callbacks RBNAME = { \
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.propagate = RBNAME ## _propagate, \
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.copy = RBNAME ## _copy, \
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.rotate = RBNAME ## _rotate \
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};
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/*
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* Template for declaring augmented rbtree callbacks,
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* computing RBAUGMENTED scalar as max(RBCOMPUTE(node)) for all subtree nodes.
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*
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* RBSTATIC: 'static' or empty
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* RBNAME: name of the rb_augment_callbacks structure
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* RBSTRUCT: struct type of the tree nodes
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* RBFIELD: name of struct rb_node field within RBSTRUCT
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* RBTYPE: type of the RBAUGMENTED field
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* RBAUGMENTED: name of RBTYPE field within RBSTRUCT holding data for subtree
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* RBCOMPUTE: name of function that returns the per-node RBTYPE scalar
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*/
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#define RB_DECLARE_CALLBACKS_MAX(RBSTATIC, RBNAME, RBSTRUCT, RBFIELD, \
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RBTYPE, RBAUGMENTED, RBCOMPUTE) \
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static inline bool RBNAME ## _compute_max(RBSTRUCT *node, bool exit) \
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{ \
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RBSTRUCT *child; \
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RBTYPE max = RBCOMPUTE(node); \
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if (node->RBFIELD.rb_left) { \
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child = rb_entry(node->RBFIELD.rb_left, RBSTRUCT, RBFIELD); \
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if (child->RBAUGMENTED > max) \
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max = child->RBAUGMENTED; \
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} \
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if (node->RBFIELD.rb_right) { \
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child = rb_entry(node->RBFIELD.rb_right, RBSTRUCT, RBFIELD); \
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if (child->RBAUGMENTED > max) \
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max = child->RBAUGMENTED; \
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} \
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if (exit && node->RBAUGMENTED == max) \
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return true; \
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node->RBAUGMENTED = max; \
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return false; \
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} \
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RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME, \
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RBSTRUCT, RBFIELD, RBAUGMENTED, RBNAME ## _compute_max)
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#define RB_RED 0
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#define RB_BLACK 1
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#define __rb_parent(pc) ((struct rb_node *)(pc & ~3))
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#define __rb_color(pc) ((pc) & 1)
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#define __rb_is_black(pc) __rb_color(pc)
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#define __rb_is_red(pc) (!__rb_color(pc))
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#define rb_color(rb) __rb_color((rb)->__rb_parent_color)
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#define rb_is_red(rb) __rb_is_red((rb)->__rb_parent_color)
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#define rb_is_black(rb) __rb_is_black((rb)->__rb_parent_color)
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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_color(rb) + (unsigned long)p;
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}
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static inline void rb_set_parent_color(struct rb_node *rb,
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struct rb_node *p, int color)
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{
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rb->__rb_parent_color = (unsigned long)p + color;
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}
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static inline void
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__rb_change_child(struct rb_node *old, struct rb_node *new,
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struct rb_node *parent, struct rb_root *root)
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{
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if (parent) {
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if (parent->rb_left == old)
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WRITE_ONCE(parent->rb_left, new);
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else
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WRITE_ONCE(parent->rb_right, new);
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} else
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WRITE_ONCE(root->rb_node, new);
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}
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static inline void
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__rb_change_child_rcu(struct rb_node *old, struct rb_node *new,
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struct rb_node *parent, struct rb_root *root)
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{
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if (parent) {
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if (parent->rb_left == old)
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rcu_assign_pointer(parent->rb_left, new);
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else
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rcu_assign_pointer(parent->rb_right, new);
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} else
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rcu_assign_pointer(root->rb_node, new);
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}
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extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
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void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
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static __always_inline struct rb_node *
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__rb_erase_augmented(struct rb_node *node, struct rb_root *root,
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const struct rb_augment_callbacks *augment)
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{
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struct rb_node *child = node->rb_right;
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struct rb_node *tmp = node->rb_left;
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struct rb_node *parent, *rebalance;
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unsigned long pc;
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if (!tmp) {
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/*
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* Case 1: node to erase has no more than 1 child (easy!)
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*
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* Note that if there is one child it must be red due to 5)
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* and node must be black due to 4). We adjust colors locally
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* so as to bypass __rb_erase_color() later on.
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*/
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pc = node->__rb_parent_color;
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parent = __rb_parent(pc);
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__rb_change_child(node, child, parent, root);
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if (child) {
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child->__rb_parent_color = pc;
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rebalance = NULL;
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} else
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rebalance = __rb_is_black(pc) ? parent : NULL;
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tmp = parent;
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} else if (!child) {
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/* Still case 1, but this time the child is node->rb_left */
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tmp->__rb_parent_color = pc = node->__rb_parent_color;
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parent = __rb_parent(pc);
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__rb_change_child(node, tmp, parent, root);
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rebalance = NULL;
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tmp = parent;
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} else {
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struct rb_node *successor = child, *child2;
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tmp = child->rb_left;
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if (!tmp) {
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/*
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* Case 2: node's successor is its right child
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*
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* (n) (s)
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* / \ / \
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* (x) (s) -> (x) (c)
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* \
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* (c)
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*/
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parent = successor;
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child2 = successor->rb_right;
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augment->copy(node, successor);
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} else {
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/*
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* Case 3: node's successor is leftmost under
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* node's right child subtree
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*
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* (n) (s)
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* / \ / \
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* (x) (y) -> (x) (y)
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* / /
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* (p) (p)
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* / /
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* (s) (c)
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* \
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* (c)
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*/
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do {
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parent = successor;
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successor = tmp;
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tmp = tmp->rb_left;
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} while (tmp);
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child2 = successor->rb_right;
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WRITE_ONCE(parent->rb_left, child2);
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WRITE_ONCE(successor->rb_right, child);
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rb_set_parent(child, successor);
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augment->copy(node, successor);
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augment->propagate(parent, successor);
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}
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tmp = node->rb_left;
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WRITE_ONCE(successor->rb_left, tmp);
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rb_set_parent(tmp, successor);
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pc = node->__rb_parent_color;
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tmp = __rb_parent(pc);
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__rb_change_child(node, successor, tmp, root);
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if (child2) {
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rb_set_parent_color(child2, parent, RB_BLACK);
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rebalance = NULL;
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} else {
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rebalance = rb_is_black(successor) ? parent : NULL;
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}
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successor->__rb_parent_color = pc;
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tmp = successor;
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}
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augment->propagate(tmp, NULL);
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return rebalance;
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}
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static __always_inline void
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rb_erase_augmented(struct rb_node *node, struct rb_root *root,
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const struct rb_augment_callbacks *augment)
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{
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struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
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if (rebalance)
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__rb_erase_color(rebalance, root, augment->rotate);
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}
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static __always_inline void
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rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root,
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const struct rb_augment_callbacks *augment)
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{
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if (root->rb_leftmost == node)
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root->rb_leftmost = rb_next(node);
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rb_erase_augmented(node, &root->rb_root, augment);
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}
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#endif /* _LINUX_RBTREE_AUGMENTED_H */
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