astobj2_rbtree.c

/*
 * astobj2_hash - RBTree implementation for astobj2.
 *
 * Copyright (C) 2006 Marta Carbone, Luigi Rizzo - Univ. di Pisa, Italy
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief RBTree functions implementing astobj2 containers.
 *
 * \author Richard Mudgett <rmudgett@digium.com>
 */

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision$")

#include "asterisk/_private.h"
#include "asterisk/astobj2.h"
#include "asterisk/utils.h"
#include "astobj2_private.h"
#include "astobj2_container_private.h"

/*!
 * A structure to hold the object held by the container and
 * where it is located in it.
 *
 * A red-black tree has the following properties:
 *
 * 1) Every node is either black or red.
 *
 * 2) The root is black.
 *
 * 3) If a node has a NULL child, that "child" is considered
 * black.
 *
 * 4) If a node is red, then both of its children are black.
 *
 * 5) Every path from a node to a descendant NULL child has the
 * same number of black nodes.  (Including the black NULL
 * child.)
 */
struct rbtree_node {
	/*!
	 * \brief Items common to all container nodes.
	 * \note Must be first in the specific node struct.
	 */
	struct ao2_container_node common;
	/*! Parent node of this node. NULL if this is the root node. */
	struct rbtree_node *parent;
	/*! Left child node of this node.  NULL if does not have this child. */
	struct rbtree_node *left;
	/*! Right child node of this node.  NULL if does not have this child. */
	struct rbtree_node *right;
	/*! TRUE if the node is red. */
	unsigned int is_red:1;
};

/*!
 * A rbtree container in addition to values common to all
 * container types, stores the pointer to the root node of the
 * tree.
 */
struct ao2_container_rbtree {
	/*!
	 * \brief Items common to all containers.
	 * \note Must be first in the specific container struct.
	 */
	struct ao2_container common;
	/*! Root node of the tree.  NULL if the tree is empty. */
	struct rbtree_node *root;
#if defined(AO2_DEBUG)
	struct {
		/*! Fixup insert left cases 1-3 */
		int fixup_insert_left[3];
		/*! Fixup insert right cases 1-3 */
		int fixup_insert_right[3];
		/*! Fixup delete left cases 1-4 */
		int fixup_delete_left[4];
		/*! Fixup delete right cases 1-4 */
		int fixup_delete_right[4];
		/*! Deletion of node with number of children (0-2). */
		int delete_children[3];
	} stats;
#endif	/* defined(AO2_DEBUG) */
};

enum equal_node_bias {
	/*! Bias search toward first matching node in the container. */
	BIAS_FIRST,
	/*! Bias search toward any matching node. */
	BIAS_EQUAL,
	/*! Bias search toward last matching node in the container. */
	BIAS_LAST,
};

enum empty_node_direction {
	GO_LEFT,
	GO_RIGHT,
};

/*! Traversal state to restart a rbtree container traversal. */
struct rbtree_traversal_state {
	/*! Active sort function in the traversal if not NULL. */
	ao2_sort_fn *sort_fn;
	/*! Saved comparison callback arg pointer. */
	void *arg;
	/*! Saved search flags to control traversing the container. */
	enum search_flags flags;
};

struct rbtree_traversal_state_check {
	/*
	 * If we have a division by zero compile error here then there
	 * is not enough room for the state.  Increase AO2_TRAVERSAL_STATE_SIZE.
	 */
	char check[1 / (AO2_TRAVERSAL_STATE_SIZE / sizeof(struct rbtree_traversal_state))];
};

/*!
 * \internal
 * \brief Get the most left node in the tree.
 * \since 12.0.0
 *
 * \param node Starting node to find the most left node.
 *
 * \return Left most node.  Never NULL.
 */
static struct rbtree_node *rb_node_most_left(struct rbtree_node *node)
{
	while (node->left) {
		node = node->left;
	}

	return node;
}

/*!
 * \internal
 * \brief Get the most right node in the tree.
 * \since 12.0.0
 *
 * \param node Starting node to find the most right node.
 *
 * \return Right most node.  Never NULL.
 */
static struct rbtree_node *rb_node_most_right(struct rbtree_node *node)
{
	while (node->right) {
		node = node->right;
	}

	return node;
}

/*!
 * \internal
 * \brief Get the next node in ascending sequence.
 * \since 12.0.0
 *
 * \param node Starting node to find the next node.
 *
 * \retval node on success.
 * \retval NULL if no node.
 */
static struct rbtree_node *rb_node_next(struct rbtree_node *node)
{
	if (node->right) {
		return rb_node_most_left(node->right);
	}

	/* Find the parent that the node is a left child of. */
	while (node->parent) {
		if (node->parent->left == node) {
			/* We are the left child.  The parent is the next node. */
			return node->parent;
		}
		node = node->parent;
	}
	return NULL;
}

/*!
 * \internal
 * \brief Get the next node in descending sequence.
 * \since 12.0.0
 *
 * \param node Starting node to find the previous node.
 *
 * \retval node on success.
 * \retval NULL if no node.
 */
static struct rbtree_node *rb_node_prev(struct rbtree_node *node)
{
	if (node->left) {
		return rb_node_most_right(node->left);
	}

	/* Find the parent that the node is a right child of. */
	while (node->parent) {
		if (node->parent->right == node) {
			/* We are the right child.  The parent is the previous node. */
			return node->parent;
		}
		node = node->parent;
	}
	return NULL;
}

/*!
 * \internal
 * \brief Get the next node in pre-order sequence.
 * \since 12.0.0
 *
 * \param node Starting node to find the next node.
 *
 * \retval node on success.
 * \retval NULL if no node.
 */
static struct rbtree_node *rb_node_pre(struct rbtree_node *node)
{
	/* Visit the children if the node has any. */
	if (node->left) {
		return node->left;
	}
	if (node->right) {
		return node->right;
	}

	/* Time to go back up. */
	for (;;) {
		if (!node->parent) {
			return NULL;
		}
		if (node->parent->left == node && node->parent->right) {
			/*
			 * We came up the left child and there's a right child.  Visit
			 * it.
			 */
			return node->parent->right;
		}
		node = node->parent;
	}
}

/*!
 * \internal
 * \brief Get the next node in post-order sequence.
 * \since 12.0.0
 *
 * \param node Starting node to find the next node.
 *
 * \retval node on success.
 * \retval NULL if no node.
 */
static struct rbtree_node *rb_node_post(struct rbtree_node *node)
{
	/* This node's children have already been visited. */
	for (;;) {
		if (!node->parent) {
			return NULL;
		}
		if (node->parent->left == node) {
			/* We came up the left child. */
			node = node->parent;

			/*
			 * Find the right child's left most childless node.
			 */
			while (node->right) {
				node = rb_node_most_left(node->right);
			}

			/*
			 * This node's left child has already been visited or it doesn't
			 * have any children.
			 */
			return node;
		}

		/*
		 * We came up the right child.
		 *
		 * This node's children have already been visited.  Time to
		 * visit the parent.
		 */
		return node->parent;
	}
}

/*!
 * \internal
 * \brief Get the next non-empty node in ascending sequence.
 * \since 12.0.0
 *
 * \param node Starting node to find the next node.
 *
 * \retval node on success.
 * \retval NULL if no node.
 */
static struct rbtree_node *rb_node_next_full(struct rbtree_node *node)
{
	for (;;) {
		node = rb_node_next(node);
		if (!node || node->common.obj) {
			return node;
		}
	}
}

/*!
 * \internal
 * \brief Get the next non-empty node in descending sequence.
 * \since 12.0.0
 *
 * \param node Starting node to find the previous node.
 *
 * \retval node on success.
 * \retval NULL if no node.
 */
static struct rbtree_node *rb_node_prev_full(struct rbtree_node *node)
{
	for (;;) {
		node = rb_node_prev(node);
		if (!node || node->common.obj) {
			return node;
		}
	}
}

/*!
 * \internal
 * \brief Determine which way to go from an empty node.
 * \since 12.0.0
 *
 * \param empty Empty node to determine which side obj_right goes on.
 * \param sort_fn Sort comparison function for non-empty nodes.
 * \param obj_right pointer to the (user-defined part) of an object.
 * \param flags flags from ao2_callback()
 *   OBJ_SEARCH_OBJECT - if set, 'obj_right', is an object.
 *   OBJ_SEARCH_KEY - if set, 'obj_right', is a search key item that is not an object.
 *   OBJ_SEARCH_PARTIAL_KEY - if set, 'obj_right', is a partial search key item that is not an object.
 * \param bias How to bias search direction for duplicates
 *
 * \return enum empty_node_direction to proceed.
 */
static enum empty_node_direction rb_find_empty_direction(struct rbtree_node *empty, ao2_sort_fn *sort_fn, void *obj_right, enum search_flags flags, enum equal_node_bias bias)
{
	int cmp;
	struct rbtree_node *cur;
	struct rbtree_node *right_most;

	/* Try for a quick definite go left. */
	if (!empty->left) {
		/* The empty node has no left child. */
		return GO_RIGHT;
	}
	right_most = rb_node_most_right(empty->left);
	if (right_most->common.obj) {
		cmp = sort_fn(right_most->common.obj, obj_right, flags);
		if (cmp < 0) {
			return GO_RIGHT;
		}
		if (cmp == 0 && bias == BIAS_LAST) {
			return GO_RIGHT;
		}
		return GO_LEFT;
	}

	/* Try for a quick definite go right. */
	if (!empty->right) {
		/* The empty node has no right child. */
		return GO_LEFT;
	}
	cur = rb_node_most_left(empty->right);
	if (cur->common.obj) {
		cmp = sort_fn(cur->common.obj, obj_right, flags);
		if (cmp > 0) {
			return GO_LEFT;
		}
		if (cmp == 0 && bias == BIAS_FIRST) {
			return GO_LEFT;
		}
		return GO_RIGHT;
	}

	/*
	 * Have to scan the previous nodes from the right_most node of
	 * the left subtree for the first non-empty node to determine
	 * direction.
	 */
	cur = right_most;
	for (;;) {
		/* Find previous node. */
		if (cur->left) {
			cur = rb_node_most_right(cur->left);
		} else {
			/* Find the parent that the node is a right child of. */
			for (;;) {
				if (cur->parent == empty) {
					/* The left side of the empty node is all empty nodes. */
					return GO_RIGHT;
				}
				if (cur->parent->right == cur) {
					/* We are the right child.  The parent is the previous node. */
					cur = cur->parent;
					break;
				}
				cur = cur->parent;
			}
		}

		if (cur->common.obj) {
			cmp = sort_fn(cur->common.obj, obj_right, flags);
			if (cmp < 0) {
				return GO_RIGHT;
			}
			if (cmp == 0 && bias == BIAS_LAST) {
				return GO_RIGHT;
			}
			return GO_LEFT;
		}
	}
}

/*!
 * \internal
 * \brief Tree node rotation left.
 * \since 12.0.0
 *
 * \param self Container holding node.
 * \param node Node to perform a left rotation with.
 *
 *        p                         p
 *        |     Left rotation       |
 *        N        --->             Ch
 *       / \                       / \
 *      a  Ch                     N   c
 *        / \                    / \
 *       b   c                  a   b
 *
 * N = node
 * Ch = child
 * p = parent
 * a,b,c = other nodes that are unaffected by the rotation.
 *
 * \note It is assumed that the node's right child exists.
 *
 * \return Nothing
 */
static void rb_rotate_left(struct ao2_container_rbtree *self, struct rbtree_node *node)
{
	struct rbtree_node *child;	/*!< Node's right child. */

	child = node->right;

	/* Link the node's parent to the child. */
	if (!node->parent) {
		/* Node is the root so we get a new root node. */
		self->root = child;
	} else if (node->parent->left == node) {
		/* Node is a left child. */
		node->parent->left = child;
	} else {
		/* Node is a right child. */
		node->parent->right = child;
	}
	child->parent = node->parent;

	/* Link node's right subtree to the child's left subtree. */
	node->right = child->left;
	if (node->right) {
		node->right->parent = node;
	}

	/* Link the node to the child's left. */
	node->parent = child;
	child->left = node;
}

/*!
 * \internal
 * \brief Tree node rotation right.
 * \since 12.0.0
 *
 * \param self Container holding node.
 * \param node Node to perform a right rotation with.
 *
 *        p                         p
 *        |     Right rotation      |
 *        Ch                        N
 *       / \       <---            / \
 *      a  N                      Ch  c
 *        / \                    / \
 *       b   c                  a   b
 *
 * N = node
 * Ch = child
 * p = parent
 * a,b,c = other nodes that are unaffected by the rotation.
 *
 * \note It is assumed that the node's left child exists.
 *
 * \return Nothing
 */
static void rb_rotate_right(struct ao2_container_rbtree *self, struct rbtree_node *node)
{
	struct rbtree_node *child;	/*!< Node's left child. */

	child = node->left;

	/* Link the node's parent to the child. */
	if (!node->parent) {
		/* Node is the root so we get a new root node. */
		self->root = child;
	} else if (node->parent->right == node) {
		/* Node is a right child. */
		node->parent->right = child;
	} else {
		/* Node is a left child. */
		node->parent->left = child;
	}
	child->parent = node->parent;

	/* Link node's left subtree to the child's right subtree. */
	node->left = child->right;
	if (node->left) {
		node->left->parent = node;
	}

	/* Link the node to the child's right. */
	node->parent = child;
	child->right = node;
}

/*!
 * \internal
 * \brief Create an empty copy of this container.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 *
 * \retval empty-clone-container on success.
 * \retval NULL on error.
 */
static struct ao2_container *rb_ao2_alloc_empty_clone(struct ao2_container_rbtree *self)
{
	if (!is_ao2_object(self)) {
		return NULL;
	}

	return ao2_t_container_alloc_rbtree(ao2_options_get(self), self->common.options,
		self->common.sort_fn, self->common.cmp_fn, "Clone rbtree container");
}

/*!
 * \internal
 * \brief Create an empty copy of this container. (Debug version)
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param tag used for debugging.
 * \param file Debug file name invoked from
 * \param line Debug line invoked from
 * \param func Debug function name invoked from
 * \param ref_debug TRUE if to output a debug reference message.
 *
 * \retval empty-clone-container on success.
 * \retval NULL on error.
 */
static struct ao2_container *rb_ao2_alloc_empty_clone_debug(struct ao2_container_rbtree *self, const char *tag, const char *file, int line, const char *func, int ref_debug)
{
	if (!is_ao2_object(self)) {
		return NULL;
	}

	return __ao2_container_alloc_rbtree_debug(ao2_options_get(self), self->common.options,
		self->common.sort_fn, self->common.cmp_fn, tag, file, line, func, ref_debug);
}

/*!
 * \internal
 * \brief Fixup the rbtree after deleting a node.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param child Child of the node just deleted from the container.
 *
 * \note The child must be a dummy black node if there really
 * was no child of the deleted node.  Otherwise, the caller must
 * pass in the parent node and which child was deleted.  In
 * addition, the fixup routine would be more complicated.
 *
 * \return Nothing
 */
static void rb_delete_fixup(struct ao2_container_rbtree *self, struct rbtree_node *child)
{
	struct rbtree_node *sibling;

	while (self->root != child && !child->is_red) {
		if (child->parent->left == child) {
			/* Child is a left child. */
			sibling = child->parent->right;
			ast_assert(sibling != NULL);
			if (sibling->is_red) {
				/* Case 1: The child's sibling is red. */
				AO2_DEVMODE_STAT(++self->stats.fixup_delete_left[0]);
				sibling->is_red = 0;
				child->parent->is_red = 1;
				rb_rotate_left(self, child->parent);
				sibling = child->parent->right;
				ast_assert(sibling != NULL);
			}
			/*
			 * The sibling is black.  A black node must have two children,
			 * or one red child, or no children.
			 */
			if ((!sibling->left || !sibling->left->is_red)
				&& (!sibling->right || !sibling->right->is_red)) {
				/*
				 * Case 2: The sibling is black and both of its children are black.
				 *
				 * This case handles the two black children or no children
				 * possibilities of a black node.
				 */
				AO2_DEVMODE_STAT(++self->stats.fixup_delete_left[1]);
				sibling->is_red = 1;
				child = child->parent;
			} else {
				/* At this point the sibling has at least one red child. */
				if (!sibling->right || !sibling->right->is_red) {
					/*
					 * Case 3: The sibling is black, its left child is red, and its
					 * right child is black.
					 */
					AO2_DEVMODE_STAT(++self->stats.fixup_delete_left[2]);
					ast_assert(sibling->left != NULL);
					ast_assert(sibling->left->is_red);
					sibling->left->is_red = 0;
					sibling->is_red = 1;
					rb_rotate_right(self, sibling);
					sibling = child->parent->right;
					ast_assert(sibling != NULL);
				}
				/* Case 4: The sibling is black and its right child is red. */
				AO2_DEVMODE_STAT(++self->stats.fixup_delete_left[3]);
				sibling->is_red = child->parent->is_red;
				child->parent->is_red = 0;
				if (sibling->right) {
					sibling->right->is_red = 0;
				}
				rb_rotate_left(self, child->parent);
				child = self->root;
			}
		} else {
			/* Child is a right child. */
			sibling = child->parent->left;
			ast_assert(sibling != NULL);
			if (sibling->is_red) {
				/* Case 1: The child's sibling is red. */
				AO2_DEVMODE_STAT(++self->stats.fixup_delete_right[0]);
				sibling->is_red = 0;
				child->parent->is_red = 1;
				rb_rotate_right(self, child->parent);
				sibling = child->parent->left;
				ast_assert(sibling != NULL);
			}
			/*
			 * The sibling is black.  A black node must have two children,
			 * or one red child, or no children.
			 */
			if ((!sibling->right || !sibling->right->is_red)
				&& (!sibling->left || !sibling->left->is_red)) {
				/*
				 * Case 2: The sibling is black and both of its children are black.
				 *
				 * This case handles the two black children or no children
				 * possibilities of a black node.
				 */
				AO2_DEVMODE_STAT(++self->stats.fixup_delete_right[1]);
				sibling->is_red = 1;
				child = child->parent;
			} else {
				/* At this point the sibling has at least one red child. */
				if (!sibling->left || !sibling->left->is_red) {
					/*
					 * Case 3: The sibling is black, its right child is red, and its
					 * left child is black.
					 */
					AO2_DEVMODE_STAT(++self->stats.fixup_delete_right[2]);
					ast_assert(sibling->right != NULL);
					ast_assert(sibling->right->is_red);
					sibling->right->is_red = 0;
					sibling->is_red = 1;
					rb_rotate_left(self, sibling);
					sibling = child->parent->left;
					ast_assert(sibling != NULL);
				}
				/* Case 4: The sibling is black and its left child is red. */
				AO2_DEVMODE_STAT(++self->stats.fixup_delete_right[3]);
				sibling->is_red = child->parent->is_red;
				child->parent->is_red = 0;
				if (sibling->left) {
					sibling->left->is_red = 0;
				}
				rb_rotate_right(self, child->parent);
				child = self->root;
			}
		}
	}

	/*
	 * Case 2 could leave the child node red and it needs to leave
	 * with it black.
	 *
	 * Case 4 sets the child node to the root which of course must
	 * be black.
	 */
	child->is_red = 0;
}

/*!
 * \internal
 * \brief Delete the doomed node from this container.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param doomed Container node to delete from the container.
 *
 * \return Nothing
 */
static void rb_delete_node(struct ao2_container_rbtree *self, struct rbtree_node *doomed)
{
	struct rbtree_node *child;
	int need_fixup;

	if (doomed->left && doomed->right) {
		struct rbtree_node *next;
		int is_red;

		/*
		 * The doomed node has two children.
		 *
		 * Find the next child node and swap it with the doomed node in
		 * the tree.
		 */
		AO2_DEVMODE_STAT(++self->stats.delete_children[2]);
		next = rb_node_most_left(doomed->right);
		SWAP(doomed->parent, next->parent);
		SWAP(doomed->left, next->left);
		SWAP(doomed->right, next->right);
		is_red = doomed->is_red;
		doomed->is_red = next->is_red;
		next->is_red = is_red;

		/* Link back in the next node. */
		if (!next->parent) {
			/* Doomed was the root so we get a new root node. */
			self->root = next;
		} else if (next->parent->left == doomed) {
			/* Doomed was the left child. */
			next->parent->left = next;
		} else {
			/* Doomed was the right child. */
			next->parent->right = next;
		}
		next->left->parent = next;
		if (next->right == next) {
			/* The next node was the right child of doomed. */
			next->right = doomed;
			doomed->parent = next;
		} else {
			next->right->parent = next;
			doomed->parent->left = doomed;
		}

		/* The doomed node has no left child now. */
		ast_assert(doomed->left == NULL);

		/*
		 * We don't have to link the right child back in with doomed
		 * since we are going to link it with doomed's parent anyway.
		 */
		child = doomed->right;
	} else {
		/* Doomed has at most one child. */
		child = doomed->left;
		if (!child) {
			child = doomed->right;
		}
	}
	if (child) {
		AO2_DEVMODE_STAT(++self->stats.delete_children[1]);
	} else {
		AO2_DEVMODE_STAT(++self->stats.delete_children[0]);
	}

	need_fixup = (!doomed->is_red && !self->common.destroying);
	if (need_fixup && !child) {
		/*
		 * Use the doomed node as a place holder node for the
		 * nonexistent child so we also don't have to pass to the fixup
		 * routine the parent and which child the deleted node came
		 * from.
		 */
		rb_delete_fixup(self, doomed);
		ast_assert(doomed->left == NULL);
		ast_assert(doomed->right == NULL);
		ast_assert(!doomed->is_red);
	}

	/* Link the child in place of doomed. */
	if (!doomed->parent) {
		/* Doomed was the root so we get a new root node. */
		self->root = child;
	} else if (doomed->parent->left == doomed) {
		/* Doomed was the left child. */
		doomed->parent->left = child;
	} else {
		/* Doomed was the right child. */
		doomed->parent->right = child;
	}
	if (child) {
		child->parent = doomed->parent;
		if (need_fixup) {
			rb_delete_fixup(self, child);
		}
	}

	AO2_DEVMODE_STAT(--self->common.nodes);
}

/*!
 * \internal
 * \brief Destroy a rbtree container node.
 * \since 12.0.0
 *
 * \param v_doomed Container node to destroy.
 *
 * \details
 * The container node unlinks itself from the container as part
 * of its destruction.  The node must be destroyed while the
 * container is already locked.
 *
 * \note The container must be locked when the node is
 * unreferenced.
 *
 * \return Nothing
 */
static void rb_ao2_node_destructor(void *v_doomed)
{
	struct rbtree_node *doomed = v_doomed;

	if (doomed->common.is_linked) {
		struct ao2_container_rbtree *my_container;

		/*
		 * Promote to write lock if not already there.  Since
		 * adjust_lock() can potentially release and block waiting for a
		 * write lock, care must be taken to ensure that node references
		 * are released before releasing the container references.
		 *
		 * Node references held by an iterator can only be held while
		 * the iterator also holds a reference to the container.  These
		 * node references must be unreferenced before the container can
		 * be unreferenced to ensure that the node will not get a
		 * negative reference and the destructor called twice for the
		 * same node.
		 */
		my_container = (struct ao2_container_rbtree *) doomed->common.my_container;
#if defined(AST_DEVMODE)
		is_ao2_object(my_container);
#endif

		__adjust_lock(my_container, AO2_LOCK_REQ_WRLOCK, 1);

#if defined(AO2_DEBUG)
		if (!my_container->common.destroying
			&& ao2_container_check(doomed->common.my_container, OBJ_NOLOCK)) {
			ast_log(LOG_ERROR, "Container integrity failed before node deletion.\n");
		}
#endif	/* defined(AO2_DEBUG) */
		rb_delete_node(my_container, doomed);
#if defined(AO2_DEBUG)
		if (!my_container->common.destroying
			&& ao2_container_check(doomed->common.my_container, OBJ_NOLOCK)) {
			ast_log(LOG_ERROR, "Container integrity failed after node deletion.\n");
		}
#endif	/* defined(AO2_DEBUG) */
	}

	/*
	 * We could have an object in the node if the container is being
	 * destroyed or the node had not been linked in yet.
	 */
	if (doomed->common.obj) {
		__container_unlink_node(&doomed->common, AO2_UNLINK_NODE_UNLINK_OBJECT);
	}
}

/*!
 * \internal
 * \brief Create a new container node.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param obj_new Object to put into the node.
 * \param tag used for debugging.
 * \param file Debug file name invoked from
 * \param line Debug line invoked from
 * \param func Debug function name invoked from
 *
 * \retval initialized-node on success.
 * \retval NULL on error.
 */
static struct rbtree_node *rb_ao2_new_node(struct ao2_container_rbtree *self, void *obj_new, const char *tag, const char *file, int line, const char *func)
{
	struct rbtree_node *node;

	node = __ao2_alloc(sizeof(*node), rb_ao2_node_destructor, AO2_ALLOC_OPT_LOCK_NOLOCK);
	if (!node) {
		return NULL;
	}

	if (tag) {
		__ao2_ref_debug(obj_new, +1, tag, file, line, func);
	} else {
		ao2_t_ref(obj_new, +1, "Container node creation");
	}
	node->common.obj = obj_new;
	node->common.my_container = (struct ao2_container *) self;

	return node;
}

/*!
 * \internal
 * \brief Fixup the rbtree after inserting a node.
 * \since 12.0.0
 *
 * \param self Container to operate upon.
 * \param node Container node just inserted into the container.
 *
 * \note The just inserted node is red.
 *
 * \return Nothing
 */
static void rb_insert_fixup(struct ao2_container_rbtree *self, struct rbtree_node *node)
{
	struct rbtree_node *g_parent;	/* Grand parent node. */

	while (node->parent && node->parent->is_red) {
		g_parent = node->parent->parent;

		/* The grand parent must exist if the parent is red. */
		ast_assert(g_parent != NULL);

		if (node->parent == g_parent->left) {
			/* The parent is a left child. */
			if (g_parent->right && g_parent->right->is_red) {
				/* Case 1: Push the black down from the grand parent node. */
				AO2_DEVMODE_STAT(++self->stats.fixup_insert_left[0]);
				g_parent->right->is_red = 0;
				g_parent->left->is_red = 0;
				g_parent->is_red = 1;

				node = g_parent;
			} else {
				/* The uncle node is black. */
				if (node->parent->right == node) {
					/*
					 * Case 2: The node is a right child.
					 *
					 * Which node is the grand parent does not change.
					 */
					AO2_DEVMODE_STAT(++self->stats.fixup_insert_left[1]);
					node = node->parent;
					rb_rotate_left(self, node);
				}
				/* Case 3: The node is a left child. */
				AO2_DEVMODE_STAT(++self->stats.fixup_insert_left[2]);
				node->parent->is_red = 0;
				g_parent->is_red = 1;
				rb_rotate_right(self, g_parent);
			}
		} else {
			/* The parent is a right child. */
			if (g_parent->left && g_parent->left->is_red) {
				/* Case 1: Push the black down from the grand parent node. */
				AO2_DEVMODE_STAT(++self->stats.fixup_insert_right[0]);