lock_free_chromatic_tree-inl.h

/*
 * Copyright (c) 2014-2015, Siemens AG. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef EMBB_CONTAINERS_INTERNAL_LOCK_FREE_CHROMATIC_TREE_INL_H_
#define EMBB_CONTAINERS_INTERNAL_LOCK_FREE_CHROMATIC_TREE_INL_H_

#include <assert.h>
#include <algorithm>

#ifdef EMBB_DEBUG
static const size_t INVALID_POINTER = static_cast<size_t>(-1);
# define VERIFY_ADDRESS(addr) assert(reinterpret_cast<size_t>((addr)) != \
                                     INVALID_POINTER)
#else
# define VERIFY_ADDRESS(address) ((void)0)
#endif

namespace embb {
namespace containers {
namespace internal {

template<typename Key, typename Value>
ChromaticTreeNode<Key, Value>::
ChromaticTreeNode(const Key& key, const Value& value, int weight,
                  Node* left, Node* right, Operation* operation)
    : key_(key),
      value_(value),
      weight_(weight < 0 ? -weight : weight),
      is_leaf_(left == NULL),
      is_sentinel_(weight < 0),
      left_(left),
      right_(right),
      retired_(false),
      operation_(operation) {}

template<typename Key, typename Value>
ChromaticTreeNode<Key, Value>::
ChromaticTreeNode(const Key& key, const Value& value, int weight,
                  Operation* operation)
    : key_(key),
      value_(value),
      weight_(weight < 0 ? -weight : weight),
      is_leaf_(true),
      is_sentinel_(weight < 0),
      left_(NULL),
      right_(NULL),
      retired_(false),
      operation_(operation) {}

template<typename Key, typename Value>
inline const Key& ChromaticTreeNode<Key, Value>::GetKey() const {
  return key_;
}

template<typename Key, typename Value>
inline const Value& ChromaticTreeNode<Key, Value>::GetValue() const {
  return value_;
}

template<typename Key, typename Value>
inline int ChromaticTreeNode<Key, Value>::GetWeight() const {
  return weight_;
}

template<typename Key, typename Value>
inline typename ChromaticTreeNode<Key, Value>::AtomicNodePtr&
ChromaticTreeNode<Key, Value>::GetLeft() {
  return left_;
}

template<typename Key, typename Value>
inline typename ChromaticTreeNode<Key, Value>::Node*
ChromaticTreeNode<Key, Value>::GetLeft() const {
  return left_.Load();
}

template<typename Key, typename Value>
inline typename ChromaticTreeNode<Key, Value>::AtomicNodePtr&
ChromaticTreeNode<Key, Value>::GetRight() {
  return right_;
}

template<typename Key, typename Value>
inline typename ChromaticTreeNode<Key, Value>::Node*
ChromaticTreeNode<Key, Value>::GetRight() const {
  return right_.Load();
}

template<typename Key, typename Value>
inline bool ChromaticTreeNode<Key, Value>::IsLeaf() const {
  return is_leaf_;
}

template<typename Key, typename Value>
inline bool ChromaticTreeNode<Key, Value>::IsSentinel() const {
  return is_sentinel_;
}

template<typename Key, typename Value>
bool ChromaticTreeNode<Key, Value>::
ReplaceChild(Node* old_child, Node* new_child) {
  bool replaced = false;

  if (left_ == old_child) {
    replaced = left_.CompareAndSwap(old_child, new_child);
  } else if (right_ == old_child) {
    replaced = right_.CompareAndSwap(old_child, new_child);
  }

  return replaced;
}

template<typename Key, typename Value>
inline void ChromaticTreeNode<Key, Value>::Retire() {
  retired_ = true;
}

template<typename Key, typename Value>
inline bool ChromaticTreeNode<Key, Value>::IsRetired() const {
  return retired_;
}

template<typename Key, typename Value>
inline typename ChromaticTreeNode<Key, Value>::AtomicOperationPtr&
ChromaticTreeNode<Key, Value>::GetOperation() {
  return operation_;
}



template<typename Key, typename Value>
ChromaticTreeOperation<Key, Value>::ChromaticTreeOperation(bool is_dummy)
    : state_(is_dummy ? STATE_COMMITTED : STATE_FREEZING),
      root_(NULL),
      root_operation_(NULL),
      num_old_nodes_(0),
      new_child_(NULL)
#ifdef EMBB_DEBUG
      , deleted_(false)
#endif
{
  for (size_t i = 0; i < MAX_NODES; ++i) {
    old_nodes_[i] = NULL;
    old_operations_[i] = NULL;
  }
}

template<typename Key, typename Value>
void ChromaticTreeOperation<Key, Value>::
SetRoot(Node* root, Operation* root_operation) {
  root_ = root;
  root_operation_ = root_operation;
}

template<typename Key, typename Value>
void ChromaticTreeOperation<Key, Value>::
SetOldNodes(Node* node1, Operation* operation1) {
  num_old_nodes_ = 1;
  old_nodes_[0]      = node1;
  old_operations_[0] = operation1;
}

template<typename Key, typename Value>
void ChromaticTreeOperation<Key, Value>::
SetOldNodes(Node* node1, Operation* operation1,
            Node* node2, Operation* operation2) {
  num_old_nodes_ = 2;
  old_nodes_[0]      = node1;
  old_operations_[0] = operation1;
  old_nodes_[1]      = node2;
  old_operations_[1] = operation2;
}

template<typename Key, typename Value>
void ChromaticTreeOperation<Key, Value>::
SetOldNodes(Node* node1, Operation* operation1,
            Node* node2, Operation* operation2,
            Node* node3, Operation* operation3) {
  num_old_nodes_ = 3;
  old_nodes_[0]      = node1;
  old_operations_[0] = operation1;
  old_nodes_[1]      = node2;
  old_operations_[1] = operation2;
  old_nodes_[2]      = node3;
  old_operations_[2] = operation3;
}

template<typename Key, typename Value>
void ChromaticTreeOperation<Key, Value>::
SetOldNodes(Node* node1, Operation* operation1,
            Node* node2, Operation* operation2,
            Node* node3, Operation* operation3,
            Node* node4, Operation* operation4) {
  num_old_nodes_ = 4;
  old_nodes_[0]      = node1;
  old_operations_[0] = operation1;
  old_nodes_[1]      = node2;
  old_operations_[1] = operation2;
  old_nodes_[2]      = node3;
  old_operations_[2] = operation3;
  old_nodes_[3]      = node4;
  old_operations_[3] = operation4;
}

template<typename Key, typename Value>
void ChromaticTreeOperation<Key, Value>::
SetOldNodes(Node* node1, Operation* operation1,
            Node* node2, Operation* operation2,
            Node* node3, Operation* operation3,
            Node* node4, Operation* operation4,
            Node* node5, Operation* operation5) {
  num_old_nodes_ = 5;
  old_nodes_[0]      = node1;
  old_operations_[0] = operation1;
  old_nodes_[1]      = node2;
  old_operations_[1] = operation2;
  old_nodes_[2]      = node3;
  old_operations_[2] = operation3;
  old_nodes_[3]      = node4;
  old_operations_[3] = operation4;
  old_nodes_[4]      = node5;
  old_operations_[4] = operation5;
}

template<typename Key, typename Value>
void ChromaticTreeOperation<Key, Value>::SetNewChild(Node* new_child) {
  new_child_ = new_child;
}

template<typename Key, typename Value>
bool ChromaticTreeOperation<Key, Value>::
Help(AtomicNodePtr& node_guard, AtomicOperationPtr& oper_guard) {
#ifdef EMBB_DEBUG
  assert(!deleted_);
#endif
  // Freezing step
  if (!FreezeAll(node_guard, oper_guard)) {
    return IsCommitted();
  }

  // All frozen step
  if (!SwitchState(STATE_FREEZING, STATE_ALL_FROZEN)) {
    return IsCommitted();
  }

  // At this point operation may no longer fail - complete it
  HelpCommit(node_guard);

  return true;
}

template<typename Key, typename Value>
void ChromaticTreeOperation<Key, Value>::HelpCommit(AtomicNodePtr& node_guard) {
#ifdef EMBB_DEBUG
  assert(!deleted_);
#endif
  HazardNodePtr node_hp(node_guard);

  // Mark step (retire old nodes)
  for (size_t i = 0; i < num_old_nodes_; ++i) {
    node_hp.ProtectSafe(old_nodes_[i]);
    if (IsCommitted()) return;
    old_nodes_[i]->Retire();
  }

  // Update step
  node_hp.ProtectSafe(root_);
  if (IsCommitted()) return;
  root_->ReplaceChild(old_nodes_[0], new_child_);

  // Commit step
  SwitchState(STATE_ALL_FROZEN, STATE_COMMITTED);
}

template<typename Key, typename Value>
void ChromaticTreeOperation<Key, Value>::HelpAbort(Node* node) {
#ifdef EMBB_DEBUG
  assert(!deleted_);
#endif
  for (size_t i = 0; i < num_old_nodes_; ++i) {
    if (old_nodes_[i] == node) {
      Unfreeze(old_nodes_[i], old_operations_[i]);
      break;
    }
  }
}

template<typename Key, typename Value>
inline bool ChromaticTreeOperation<Key, Value>::IsAborted() {
#ifdef EMBB_DEBUG
  assert(!deleted_);
#endif
  return state_ == STATE_ABORTED;
}

template<typename Key, typename Value>
inline bool ChromaticTreeOperation<Key, Value>::IsInProgress() {
#ifdef EMBB_DEBUG
  assert(!deleted_);
#endif
  State state = state_.Load();
  return (state != STATE_ABORTED && state != STATE_COMMITTED);
}

template<typename Key, typename Value>
inline bool ChromaticTreeOperation<Key, Value>::IsCommitted() {
#ifdef EMBB_DEBUG
  assert(!deleted_);
#endif
  return state_ == STATE_COMMITTED;
}

template<typename Key, typename Value>
void ChromaticTreeOperation<Key, Value>::CleanUp(Operation* retired_dummy) {
#ifdef EMBB_DEBUG
  assert(!deleted_);
#endif
  assert(!IsInProgress());

  if (IsCommitted()) {
    for (size_t i = 0; i < num_old_nodes_; ++i) {
      assert(old_nodes_[i]->GetOperation() == this);
      old_nodes_[i]->GetOperation() = retired_dummy;
    }
  }
}

#ifdef EMBB_DEBUG
template<typename Key, typename Value>
void ChromaticTreeOperation<Key, Value>::SetDeleted() {
  deleted_ = true;
}
#endif

template<typename Key, typename Value>
bool ChromaticTreeOperation<Key, Value>::IsRollingBack() {
  State state = state_.Load();
  return (state == STATE_ROLLBACK || state == STATE_ABORTED);
}

template<typename Key, typename Value>
bool ChromaticTreeOperation<Key, Value>::IsFreezing() {
  return state_ == STATE_FREEZING;
}

template<typename Key, typename Value>
bool ChromaticTreeOperation<Key, Value>::IsAllFrozen() {
  State state = state_.Load();
  return (state == STATE_ALL_FROZEN || state == STATE_COMMITTED);
}

template<typename Key, typename Value>
bool ChromaticTreeOperation<Key, Value>::
FreezeAll(AtomicNodePtr& node_guard, AtomicOperationPtr& oper_guard) {
  if (IsFreezing()) {
    HazardNodePtr      node_hp(node_guard);
    HazardOperationPtr oper_hp(oper_guard);

    node_hp.ProtectSafe(root_);
    oper_hp.ProtectSafe(root_operation_);

    if (IsFreezing()) {
      Freeze(root_, root_operation_);
    }

    for (size_t i = 0; i < num_old_nodes_; ++i) {
      node_hp.ProtectSafe(old_nodes_[i]);
      oper_hp.ProtectSafe(old_operations_[i]);
      if (!IsFreezing()) break;

      Freeze(old_nodes_[i], old_operations_[i]);
    }
  }

  if (IsRollingBack()) {
    UnfreezeAll(node_guard);
    return false;
  }

  return true;
}

template<typename Key, typename Value>
bool ChromaticTreeOperation<Key, Value>::
Freeze(Node* node, Operation* operation) {
  bool freezed = node->GetOperation().CompareAndSwap(operation, this);

  if (!freezed && operation != this && !IsAllFrozen()) {
    // Node is frozen for another operation - abort "this"
    SwitchState(STATE_FREEZING, STATE_ROLLBACK);

    // If the "operation" was aborted and rolled back, some other thread could
    // have helped "this" to freeze all nodes, and the previous "SwitchState"
    // would fail
    return IsAllFrozen();
  }

  if (freezed && IsRollingBack()) {
    // "False-positive" CAS: "this" was aborted and the "operation" might have
    // been rolled back; While "node" is hazard protected, unfreeze it again
    Unfreeze(node, operation);
    return false;
  }

  return true;
}

template<typename Key, typename Value>
void ChromaticTreeOperation<Key, Value>::
UnfreezeAll(AtomicNodePtr& node_guard) {
  HazardNodePtr node_hp(node_guard);

  node_hp.ProtectSafe(root_);
  if (IsAborted()) return;

  Unfreeze(root_, root_operation_);

  for (size_t i = 0; i < num_old_nodes_; ++i) {
    node_hp.ProtectSafe(old_nodes_[i]);
    if (IsAborted()) return;

    Unfreeze(old_nodes_[i], old_operations_[i]);
  }

  SwitchState(STATE_ROLLBACK, STATE_ABORTED);
}

template<typename Key, typename Value>
void ChromaticTreeOperation<Key, Value>::
Unfreeze(Node* node, Operation* operation) {
  Operation* expected = this;
  node->GetOperation().CompareAndSwap(expected, operation);
}

template<typename Key, typename Value>
bool ChromaticTreeOperation<Key, Value>::
SwitchState(State old_state, State new_state) {
  if (state_ != new_state) {
    bool switched = state_.CompareAndSwap(old_state, new_state);

    if (!switched && old_state != new_state) {
      return false;
    }
  }

  return true;
}

} // namespace internal


template<typename Key, typename Value, typename Compare, typename ValuePool>
ChromaticTree<Key, Value, Compare, ValuePool>::
ChromaticTree(size_t capacity, Key undefined_key, Value undefined_value,
              Compare compare)
#ifdef EMBB_PLATFORM_COMPILER_MSVC
#pragma warning(push)
#pragma warning(disable:4355)
#endif
    : node_hazard_manager_(
          embb::base::Function<void, Node*>(*this, &ChromaticTree::FreeNode),
          NULL, HIDX_MAX),
      operation_hazard_manager_(
          embb::base::Function<void, Operation*>(*this,
                                                 &ChromaticTree::FreeOperation),
          NULL, HIDX_MAX),
#ifdef EMBB_PLATFORM_COMPILER_MSVC
#pragma warning(pop)
#endif
      undefined_key_(undefined_key),
      undefined_value_(undefined_value),
      compare_(compare),
      capacity_(capacity),
      node_pool_(2 + 5 + 2 * capacity_ +
                 node_hazard_manager_.GetRetiredListMaxSize() *
                 embb::base::Thread::GetThreadsMaxCount()),
      operation_pool_(2 + 5 + 2 * capacity_ +
                      operation_hazard_manager_.GetRetiredListMaxSize() *
                      embb::base::Thread::GetThreadsMaxCount()),
      initial_operation_dummy_(true),
      retired_operation_dummy_(true),
      entry_(node_pool_.Allocate(undefined_key_, undefined_value_, -1,
                                 node_pool_.Allocate(undefined_key_,
                                                     undefined_value_,
                                                     -1,
                                                     &initial_operation_dummy_),
                                 static_cast<Node*>(NULL),
                                 &initial_operation_dummy_)) {
  assert(entry_ != NULL);
  assert(entry_->GetLeft() != NULL);
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
ChromaticTree<Key, Value, Compare, ValuePool>::
~ChromaticTree() {
  Destruct(entry_->GetLeft());
  FreeNode(entry_);
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
bool ChromaticTree<Key, Value, Compare, ValuePool>::
Get(const Key& key, Value& value) {
  HazardNodePtr grandparent(GetNodeGuard(HIDX_GRANDPARENT));
  HazardNodePtr parent(GetNodeGuard(HIDX_PARENT));
  HazardNodePtr leaf(GetNodeGuard(HIDX_LEAF));
  Search(key, leaf, parent, grandparent);

  bool keys_are_equal = !leaf->IsSentinel() &&
                        !(compare_(key, leaf->GetKey()) ||
                          compare_(leaf->GetKey(), key));

  if (keys_are_equal) {
    value = leaf->GetValue();
  }

  return keys_are_equal;
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
bool ChromaticTree<Key, Value, Compare, ValuePool>::
TryInsert(const Key& key, const Value& value) {
  Value old_value;
  return TryInsert(key, value, old_value);
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
bool ChromaticTree<Key, Value, Compare, ValuePool>::
TryInsert(const Key& key, const Value& value, Value& old_value) {
  Node* new_leaf = NULL;
  Node* new_sibling = NULL;
  Node* new_parent = NULL;
  bool insertion_succeeded = false;
  bool added_violation = false;

  while (!insertion_succeeded) {
    HazardNodePtr grandparent(GetNodeGuard(HIDX_GRANDPARENT));
    HazardNodePtr parent(GetNodeGuard(HIDX_PARENT));
    HazardNodePtr leaf(GetNodeGuard(HIDX_LEAF));
    Search(key, leaf, parent, grandparent);

    // Protect the parent
    HazardOperationPtr parent_op(GetOperationGuard(HIDX_PARENT));
    if (!WeakLLX(parent, parent_op)) continue;
    // Verify that the leaf is still the parent's child
    if (!HasChild(parent, leaf)) continue;

    // Protect the leaf
    HazardOperationPtr leaf_op(GetOperationGuard(HIDX_LEAF));
    if (!WeakLLX(leaf, leaf_op)) continue;

    bool keys_are_equal = !leaf->IsSentinel() &&
                          !(compare_(key, leaf->GetKey()) ||
                            compare_(leaf->GetKey(), key));
    if (keys_are_equal) {
      // Reached leaf has a matching key: replace it with a new copy
      old_value = leaf->GetValue();
      new_parent = node_pool_.Allocate(key, value, leaf->GetWeight(),
                                       &initial_operation_dummy_);
      if (new_parent == NULL) break;

    // Reached leaf has a different key: add a new leaf
    } else {
      old_value = undefined_value_;

      new_leaf = node_pool_.Allocate(key, value, 1,
                                     &initial_operation_dummy_);
      if (new_leaf == NULL) break;
      new_sibling = node_pool_.Allocate(leaf->GetKey(), leaf->GetValue(), 1,
                                        &initial_operation_dummy_);
      if (new_sibling == NULL) break;

      int new_weight =
          leaf->IsSentinel() ? -1 :
            parent->IsSentinel() ? 1 :
              (leaf->GetWeight() - 1);
      if (leaf->IsSentinel() || compare_(key, leaf->GetKey())) {
        new_parent = node_pool_.Allocate(leaf->GetKey(), undefined_value_,
                                         new_weight, new_leaf, new_sibling,
                                         &initial_operation_dummy_);
      } else {
        new_parent = node_pool_.Allocate(key, undefined_value_,
                                         new_weight, new_sibling, new_leaf,
                                         &initial_operation_dummy_);
      }
      if (new_parent == NULL) break;
    }

    // Create and fill the operation object
    HazardOperationPtr insert_op(GetOperationGuard(HIDX_CURRENT_OP));
    insert_op.ProtectSafe(operation_pool_.Allocate());
    if (insert_op == NULL) break;
    insert_op->SetRoot(parent, parent_op);
    insert_op->SetOldNodes(leaf, leaf_op);
    insert_op->SetNewChild(new_parent);

    // Execute operation
    insertion_succeeded = insert_op->Help(GetNodeGuard(HIDX_HELPING),
                                          GetOperationGuard(HIDX_HELPING));
    insert_op->CleanUp(&retired_operation_dummy_);

    // If operation failed
    if (!insertion_succeeded) {
      // Retire failed operation
      RetireOperation(insert_op);
      // Delete new nodes
      FreeNode(new_parent); new_parent = NULL;
      if (!keys_are_equal) {
        FreeNode(new_leaf); new_leaf = NULL;
        FreeNode(new_sibling); new_sibling = NULL;
      }
      // Restart from scratch
      continue;
    }

    // Retire old operation objects
    RetireOperation(parent_op);
    RetireOperation(leaf_op);
    // Retire old nodes
    RetireNode(leaf);

    added_violation = (parent->GetWeight() == 0 &&
                       new_parent->GetWeight() == 0);
  }

  if (insertion_succeeded) {
    if (added_violation) CleanUp(key);
  } else {
    if (new_leaf != NULL)    FreeNode(new_leaf);
    if (new_sibling != NULL) FreeNode(new_sibling);
    if (new_parent != NULL)  FreeNode(new_parent);
  }

  return insertion_succeeded;
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
bool ChromaticTree<Key, Value, Compare, ValuePool>::
TryDelete(const Key& key) {
  Value old_value;
  return TryDelete(key, old_value);
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
bool ChromaticTree<Key, Value, Compare, ValuePool>::
TryDelete(const Key& key, Value& old_value) {
  Node* new_leaf = NULL;
  bool deletion_succeeded = false;
  bool added_violation = false;

  while (!deletion_succeeded) {
    HazardNodePtr grandparent(GetNodeGuard(HIDX_GRANDPARENT));
    HazardNodePtr parent(GetNodeGuard(HIDX_PARENT));
    HazardNodePtr leaf(GetNodeGuard(HIDX_LEAF));
    Search(key, leaf, parent, grandparent);

    // Reached leaf has a different key - nothing to delete
    if (leaf->IsSentinel() || (compare_(key, leaf->GetKey()) ||
                             compare_(leaf->GetKey(), key))) {
      old_value = undefined_value_;
      deletion_succeeded = true;
      break;
    }

    // Protect the grandparent
    HazardOperationPtr grandparent_op(GetOperationGuard(HIDX_GRANDPARENT));
    if (!WeakLLX(grandparent, grandparent_op)) continue;
    // Verify that the parent is still the child of grandparent
    if (!HasChild(grandparent, parent)) continue;

    // Protect the parent
    HazardOperationPtr parent_op(GetOperationGuard(HIDX_PARENT));
    if (!WeakLLX(parent, parent_op)) continue;

    // Get the sibling (and protect it with hazard pointer)
    HazardNodePtr sibling(GetNodeGuard(HIDX_SIBLING));
    sibling.ProtectHazard((parent->GetLeft() == leaf) ?
                          parent->GetRight() : parent->GetLeft());
    if (parent->IsRetired() || !sibling.IsActive()) continue;
    VERIFY_ADDRESS(static_cast<Node*>(sibling));

    // Verify that the leaf is still the parent's child
    if (!HasChild(parent, leaf)) continue;

    // Protect the sibling
    HazardOperationPtr sibling_op(GetOperationGuard(HIDX_SIBLING));
    if (!WeakLLX(sibling, sibling_op)) continue;

    // Protect the leaf
    HazardOperationPtr leaf_op(GetOperationGuard(HIDX_LEAF));
    if (!WeakLLX(leaf, leaf_op)) continue;

    int new_weight =
        parent->IsSentinel() ? -1 :
          grandparent->IsSentinel() ? 1 :
            (parent->GetWeight() + sibling->GetWeight());

    new_leaf = node_pool_.Allocate(
        sibling->GetKey(), sibling->GetValue(), new_weight,
        sibling->GetLeft(), sibling->GetRight(), &initial_operation_dummy_);
    if (new_leaf == NULL) break;

    old_value = leaf->GetValue();

    // Create and fill the operation object
    HazardOperationPtr delete_op(GetOperationGuard(HIDX_CURRENT_OP));
    delete_op.ProtectSafe(operation_pool_.Allocate());
    if (delete_op == NULL) break;
    delete_op->SetRoot(grandparent, grandparent_op);
    delete_op->SetOldNodes(parent, parent_op, leaf, leaf_op, sibling, sibling_op);
    delete_op->SetNewChild(new_leaf);

    // Execute operation
    deletion_succeeded = delete_op->Help(GetNodeGuard(HIDX_HELPING),
                                         GetOperationGuard(HIDX_HELPING));
    delete_op->CleanUp(&retired_operation_dummy_);

    // If operation failed
    if (!deletion_succeeded) {
      // Retire failed operation
      RetireOperation(delete_op);
      // Delete new nodes
      FreeNode(new_leaf);
      // Restart from scratch
      continue;
    }

    // Retire old operation objects
    RetireOperation(grandparent_op);
    RetireOperation(parent_op);
    RetireOperation(leaf_op);
    RetireOperation(sibling_op);
    // Retire old nodes
    RetireNode(parent);
    RetireNode(leaf);
    RetireNode(sibling);

    added_violation =  (new_weight > 1);
  }

  if (deletion_succeeded) {
    if (added_violation) CleanUp(key);
  } else {
    if (new_leaf != NULL)    FreeNode(new_leaf);
  }

  return deletion_succeeded;
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
size_t ChromaticTree<Key, Value, Compare, ValuePool>::
GetCapacity() const {
  return capacity_;
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
const Value& ChromaticTree<Key, Value, Compare, ValuePool>::
GetUndefinedValue() const {
  return undefined_value_;
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
inline bool ChromaticTree<Key, Value, Compare, ValuePool>::
IsEmpty() const {
  return entry_->GetLeft()->IsLeaf();
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
void ChromaticTree<Key, Value, Compare, ValuePool>::
Search(const Key& key, HazardNodePtr& leaf, HazardNodePtr& parent,
       HazardNodePtr& grandparent) {
  bool reached_leaf = false;

  while (!reached_leaf) {
    grandparent.ProtectSafe(entry_);
    parent.ProtectSafe(entry_);
    leaf.ProtectSafe(entry_);

    reached_leaf = leaf->IsLeaf();
    while (!reached_leaf) {
      grandparent.AdoptHazard(parent);
      parent.AdoptHazard(leaf);

      AtomicNodePtr& next_leaf =
          (leaf->IsSentinel() || compare_(key, leaf->GetKey())) ?
            leaf->GetLeft() : leaf->GetRight();

      // Parent is protected, so we can tolerate a changing child pointer
      while(!leaf.ProtectHazard(next_leaf));

      // Parent is retired - make sure it is actually removed from the tree
      if (parent->IsRetired()) {
        HazardOperationPtr op(GetOperationGuard(HIDX_HELPING));
        if (op.ProtectHazard(parent->GetOperation())) {
          op->HelpCommit(GetNodeGuard(HIDX_HELPING));
        }
        // Can't follow a child pointer in a retired node - restart from root
        break;
      }

      VERIFY_ADDRESS(static_cast<Node*>(leaf));

      reached_leaf = leaf->IsLeaf();
    }
  }
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
inline bool ChromaticTree<Key, Value, Compare, ValuePool>::
HasChild(const Node* parent, const Node* child) const {
  return (parent->GetLeft() == child || parent->GetRight() == child);
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
void ChromaticTree<Key, Value, Compare, ValuePool>::
Destruct(Node* node) {
  if (!node->IsLeaf()) {
    Destruct(node->GetLeft());
    Destruct(node->GetRight());
  }
  FreeNode(node);
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
int ChromaticTree<Key, Value, Compare, ValuePool>::
GetHeight(const Node* node) const {
  int height = 0;
  if (node != NULL) {
    height = 1 + ::std::max(GetHeight(node->GetLeft()),
                            GetHeight(node->GetRight()));
  }
  return height;
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
bool ChromaticTree<Key, Value, Compare, ValuePool>::
IsBalanced() const {
  return IsBalanced(entry_->GetLeft());
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
bool ChromaticTree<Key, Value, Compare, ValuePool>::
IsBalanced(const Node* node) const {
  // Overweight violation
  bool has_violation = node->GetWeight() > 1;

  if (!has_violation && !node->IsLeaf()) {
    const Node* left  = node->GetLeft();
    const Node* right = node->GetRight();

    // Red-red violation
    has_violation = node->GetWeight() == 0 &&
                    (left->GetWeight() == 0 || right->GetWeight() == 0);

    // Check children
    if (!has_violation) {
      has_violation = !IsBalanced(left) || !IsBalanced(right);
    }
  }

  return !has_violation;
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
bool ChromaticTree<Key, Value, Compare, ValuePool>::
IsDummyOperation(const Operation* operation) const {
  return (operation == &initial_operation_dummy_ ||
          operation == &retired_operation_dummy_);
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
void ChromaticTree<Key, Value, Compare, ValuePool>::
RetireNode(HazardNodePtr& node) {
  node_hazard_manager_.EnqueuePointerForDeletion(node.ReleaseHazard());
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
void ChromaticTree<Key, Value, Compare, ValuePool>::
RetireOperation(HazardOperationPtr& operation) {
  Operation* op = operation.ReleaseHazard();
  // Make sure we don't return the static dummy-operations to the pool
  if (!IsDummyOperation(op)) {
    operation_hazard_manager_.EnqueuePointerForDeletion(op);
  }
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
typename ChromaticTree<Key, Value, Compare, ValuePool>::AtomicNodePtr&
ChromaticTree<Key, Value, Compare, ValuePool>::
GetNodeGuard(HazardIndex index) {
  return node_hazard_manager_.GetGuardedPointer(static_cast<int>(index));
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
typename ChromaticTree<Key, Value, Compare, ValuePool>::AtomicOperationPtr&
ChromaticTree<Key, Value, Compare, ValuePool>::
GetOperationGuard(HazardIndex index) {
  return operation_hazard_manager_.GetGuardedPointer(static_cast<int>(index));
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
bool ChromaticTree<Key, Value, Compare, ValuePool>::
WeakLLX(HazardNodePtr& node, HazardOperationPtr& operation) {
  // Make sure we have a protected operation pointer
  while (!operation.ProtectHazard(node->GetOperation()));

  // Node is not retired and operation is committed - node is available
  if (!node->IsRetired() && operation->IsCommitted()) {
    return true;
  }

  if (operation->IsAborted()) {
    // Operation is aborted, but the node is still frozen - unfreeze it
    operation->HelpAbort(node);

  } else if (operation->IsInProgress()) {
    // Operation is still in progress - help it
    operation->Help(GetNodeGuard(HIDX_HELPING),
                    GetOperationGuard(HIDX_HELPING));
  }

  // LLX failed - operation pointer should not be exposed
  operation.ReleaseHazard();

  return false;
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
void ChromaticTree<Key, Value, Compare, ValuePool>::
FreeNode(Node* node) {
#ifdef EMBB_DEBUG
  node->GetLeft()  = reinterpret_cast<Node*>(INVALID_POINTER);
  node->GetRight() = reinterpret_cast<Node*>(INVALID_POINTER);
#endif
  node_pool_.Free(node);
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
void ChromaticTree<Key, Value, Compare, ValuePool>::
FreeOperation(Operation* operation) {
#ifdef EMBB_DEBUG
  operation->SetDeleted();
#endif
  operation_pool_.Free(operation);
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
bool ChromaticTree<Key, Value, Compare, ValuePool>::
CleanUp(const Key& key) {
  HazardNodePtr grandgrandparent(GetNodeGuard(HIDX_GRANDGRANDPARENT));
  HazardNodePtr grandparent(GetNodeGuard(HIDX_GRANDPARENT));
  HazardNodePtr parent(GetNodeGuard(HIDX_PARENT));
  HazardNodePtr leaf(GetNodeGuard(HIDX_LEAF));
  bool reached_leaf = false;

  while (!reached_leaf) {
    bool found_violation = false;

    grandgrandparent.ProtectSafe(entry_);
    grandparent.ProtectSafe(entry_);
    parent.ProtectSafe(entry_);
    leaf.ProtectSafe(entry_);

    reached_leaf = leaf->IsLeaf();
    while (!reached_leaf && !found_violation) {
      grandgrandparent.AdoptHazard(grandparent);
      grandparent.AdoptHazard(parent);
      parent.AdoptHazard(leaf);

      AtomicNodePtr& next_leaf =
          (leaf->IsSentinel() || compare_(key, leaf->GetKey())) ?
            leaf->GetLeft() : leaf->GetRight();

      // Parent is protected, so we can tolerate a changing child pointer
      while(!leaf.ProtectHazard(next_leaf));

      // Parent is retired - make sure it is actually removed from the tree
      if (parent->IsRetired()) {
        HazardOperationPtr op(GetOperationGuard(HIDX_HELPING));
        if (op.ProtectHazard(parent->GetOperation())) {
          op->HelpCommit(GetNodeGuard(HIDX_HELPING));
        }
        // Can't follow a child pointer in a retired node - restart from root
        break;
      }

      VERIFY_ADDRESS(static_cast<Node*>(leaf));

      // Check for violations
      if ((leaf->GetWeight() > 1) || (leaf->GetWeight() == 0 &&
                                      parent->GetWeight() == 0)) {
        if (Rebalance(grandgrandparent, grandparent, parent, leaf) ==
            EMBB_NOMEM) {
          assert(false && "No memory for rebalancing!");
          return false;
        }
        break;
      }

      reached_leaf = leaf->IsLeaf();
    }
  }

  return true;
}

#define PROTECT_NODE_WITH_LLX(h_idx, node, op_name) \
    HazardOperationPtr op_name(GetOperationGuard(h_idx)); \
    if (!WeakLLX(node, op_name)) return EMBB_BUSY

#define DEFINE_HAZARDOUS_NODE(h_idx, node, parent, method) \
    HazardNodePtr node(GetNodeGuard(h_idx)); \
    node.ProtectHazard(parent->method()); \
    if (parent->IsRetired() || !node.IsActive()) return EMBB_BUSY; \
    VERIFY_ADDRESS(static_cast<Node*>(node))

template<typename Key, typename Value, typename Compare, typename ValuePool>
embb_errors_t ChromaticTree<Key, Value, Compare, ValuePool>::
Rebalance(HazardNodePtr& u, HazardNodePtr& ux, HazardNodePtr& uxx,
          HazardNodePtr& uxxx) {
  // Protect node 'u'
  PROTECT_NODE_WITH_LLX(HIDX_U, u, u_op);
  // Verify that ux is still a child of u
  if (!HasChild(u, ux)) return EMBB_BUSY;

  // Protect node 'ux'
  PROTECT_NODE_WITH_LLX(HIDX_UX, ux, ux_op);
  // Get children of 'ux'
  DEFINE_HAZARDOUS_NODE(HIDX_UXL, uxl, ux, GetLeft);
  DEFINE_HAZARDOUS_NODE(HIDX_UXR, uxr, ux, GetRight);
  // Verify that 'uxx' is still a child of 'ux'
  bool uxx_is_left = (uxx == uxl); (void)uxx_is_left;
  if (!HasChild(ux, uxx)) return EMBB_BUSY;

  // Protect node 'uxx'
  PROTECT_NODE_WITH_LLX(HIDX_UXX, uxx, uxx_op);
  // Get children of 'uxx'
  DEFINE_HAZARDOUS_NODE(HIDX_UXXL, uxxl, uxx, GetLeft);
  DEFINE_HAZARDOUS_NODE(HIDX_UXXR, uxxr, uxx, GetRight);
  // Verify that 'uxxx' is still a child of 'uxx'
  bool uxxx_is_left = (uxxx == uxxl);
  if (!HasChild(uxx, uxxx)) return EMBB_BUSY;

  if (uxxx->GetWeight() > 1) {
    if (uxxx_is_left) {
      // Protect node 'uxxl'
      PROTECT_NODE_WITH_LLX(HIDX_UXXL, uxxl, uxxl_op);
      return OverweightLeft(u, u_op, ux, ux_op, uxx, uxx_op, uxl, uxr,
                            uxxl, uxxl_op, uxxr, uxx_is_left);
    } else {
      // Protect node 'uxxr'
      PROTECT_NODE_WITH_LLX(HIDX_UXXR, uxxr, uxxr_op);
      return OverweightRight(u, u_op, ux, ux_op, uxx, uxx_op, uxl, uxr,
                             uxxl, uxxr, uxxr_op, !uxx_is_left);
    }
  } else {
    assert(uxxx->GetWeight() == 0 && uxx->GetWeight() == 0); //Red-red violation
    if (uxx_is_left) {
      if (uxr->GetWeight() == 0) {
        // Protect node 'uxr'
        PROTECT_NODE_WITH_LLX(HIDX_UXR, uxr, uxr_op);
        return BLK(u, u_op, ux, ux_op, uxx, uxx_op, uxr, uxr_op);
      } else if (uxxx_is_left) {
        return RB1_L(u, u_op, ux, ux_op, uxx, uxx_op);
      } else {
        // Protect node 'uxxr'
        PROTECT_NODE_WITH_LLX(HIDX_UXXR, uxxr, uxxr_op);
        return RB2_L(u, u_op, ux, ux_op, uxx, uxx_op, uxxr, uxxr_op);
      }
    } else {
      if (uxl->GetWeight() == 0) {
        // Protect node 'uxl'
        PROTECT_NODE_WITH_LLX(HIDX_UXL, uxl, uxl_op);
        return BLK(u, u_op, ux, ux_op, uxl, uxl_op, uxx, uxx_op);
      } else if (!uxxx_is_left) {
        return RB1_R(u, u_op, ux, ux_op, uxx, uxx_op);
      } else {
        // Protect node 'uxxl'
        PROTECT_NODE_WITH_LLX(HIDX_UXXL, uxxl, uxxl_op);
        return RB2_R(u, u_op, ux, ux_op, uxx, uxx_op, uxxl, uxxl_op);
      }
    }
  }
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
embb_errors_t ChromaticTree<Key, Value, Compare, ValuePool>::
OverweightLeft(HazardNodePtr& u, HazardOperationPtr& u_op,
               HazardNodePtr& ux, HazardOperationPtr& ux_op,
               HazardNodePtr& uxx, HazardOperationPtr& uxx_op,
               HazardNodePtr& uxl, HazardNodePtr& uxr,
               HazardNodePtr& uxxl, HazardOperationPtr& uxxl_op,
               HazardNodePtr& uxxr, bool uxx_is_left) {
  // Let "Root" be the top of the overweight violation decision tree (see p.30)
  // Root -> Middle
  if (uxxr->GetWeight() == 0) {
    // Root -> Middle -> Left
    if (uxx->GetWeight() == 0) {
      // Root -> Middle -> Left -> Left
      if (uxx_is_left) {
        // Root -> Middle -> Left -> Left -> Left
        if (uxr->GetWeight() == 0) {
          // Protect node 'uxr'
          PROTECT_NODE_WITH_LLX(HIDX_UXR, uxr, uxr_op);
          return BLK(u, u_op, ux, ux_op, uxx, uxx_op, uxr, uxr_op);

        // Root -> Middle -> Left -> Left -> Right
        } else {
          assert(uxr->GetWeight() > 0);
          // Protect node 'uxxr'
          PROTECT_NODE_WITH_LLX(HIDX_UXXR, uxxr, uxxr_op);
          return RB2_L(u, u_op, ux, ux_op, uxx, uxx_op, uxxr, uxxr_op);
        }

      // Root -> Middle -> Left -> Right
      } else {
        assert(!uxx_is_left);
        // Root -> Middle -> Left -> Right -> Left
        if (uxl->GetWeight() == 0) {
          // Protect node 'uxl'
          PROTECT_NODE_WITH_LLX(HIDX_UXL, uxl, uxl_op);
          return BLK(u, u_op, ux, ux_op, uxl, uxl_op, uxx, uxx_op);

        // Root -> Middle -> Left -> Right -> Right
        } else {
          assert(uxl->GetWeight() > 0);
          return RB1_R(u, u_op, ux, ux_op, uxx, uxx_op);
        }
      }

    // Root -> Middle -> Right
    } else {
      assert(uxx->GetWeight() > 0);
      // Protect node 'uxxr'
      PROTECT_NODE_WITH_LLX(HIDX_UXXR, uxxr, uxxr_op);

      // Get left child of 'uxxr'
      // Note: we know that 'uxxr' is not a leaf because it has weight 0.
      DEFINE_HAZARDOUS_NODE(HIDX_UXXRL, uxxrl, uxxr, GetLeft);

      // Protect node 'uxxrl'
      PROTECT_NODE_WITH_LLX(HIDX_UXXRL, uxxrl, uxxrl_op);

      // Root -> Middle -> Right -> Left
      if (uxxrl->GetWeight() == 0) {
        return RB2_R(ux, ux_op, uxx, uxx_op,
                     uxxr, uxxr_op, uxxrl, uxxrl_op);

      // Root -> Middle -> Right -> Middle
      } else if (uxxrl->GetWeight() == 1) {
        DEFINE_HAZARDOUS_NODE(HIDX_UXXRLR, uxxrlr, uxxrl, GetRight);
        if (uxxrlr == NULL) return EMBB_BUSY;

        // Root -> Middle -> Right -> Middle -> Left
        if (uxxrlr->GetWeight() == 0) {
          // Protect node 'uxxrlr'
          PROTECT_NODE_WITH_LLX(HIDX_UXXRLR, uxxrlr, uxxrlr_op);
          return W4_L(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op,
                      uxxr, uxxr_op, uxxrl, uxxrl_op, uxxrlr, uxxrlr_op);

        // Root -> Middle -> Right -> Middle -> Right
        } else {
          assert(uxxrlr->GetWeight() > 0);
          // Root -> Middle -> Right -> Middle -> Right -> Left
          // Node: reusing hazard of node 'uxxrlr' as it is no longer used
          DEFINE_HAZARDOUS_NODE(HIDX_UXXRLL, uxxrll, uxxrl, GetLeft);
          if (uxxrll->GetWeight() == 0) {
            // Protect node 'uxxrll'
            PROTECT_NODE_WITH_LLX(HIDX_UXXRLL, uxxrll, uxxrll_op);
            return W3_L(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op, uxxr,
                        uxxr_op, uxxrl, uxxrl_op, uxxrll, uxxrll_op);

          // Root -> Middle -> Right -> Middle -> Right -> Right
          } else {
            assert(uxxrll->GetWeight() > 0);
            return W2_L(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op,
                        uxxr, uxxr_op, uxxrl, uxxrl_op);
          }
        }

      // Root -> Middle -> Right -> Right
      } else {
        assert(uxxrl->GetWeight() > 1);
        return W1_L(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op,
                    uxxr, uxxr_op, uxxrl, uxxrl_op);
      }
    }

  // Root -> Right
  } else if (uxxr->GetWeight() == 1) {
    // Protect node 'uxxr'
    PROTECT_NODE_WITH_LLX(HIDX_UXXR, uxxr, uxxr_op);
    // Get children of 'uxxr'
    DEFINE_HAZARDOUS_NODE(HIDX_UXXRL, uxxrl, uxxr, GetLeft);
    DEFINE_HAZARDOUS_NODE(HIDX_UXXRR, uxxrr, uxxr, GetRight);
    if (uxxrl == NULL) return EMBB_BUSY;

    // Root -> Right -> Left
    if (uxxrr->GetWeight() == 0) {
      // Protect node 'uxxrr'
      PROTECT_NODE_WITH_LLX(HIDX_UXXRR, uxxrr, uxxrr_op);
      return W5_L(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op,
                  uxxr, uxxr_op, uxxrr, uxxrr_op);

    // Root -> Right -> Right
    } else {
      assert(uxxrr->GetWeight() > 0);
      // Root -> Right -> Right -> Left
      if (uxxrl->GetWeight() == 0) {
        // Protect node 'uxxrl'
        PROTECT_NODE_WITH_LLX(HIDX_UXXRL, uxxrl, uxxrl_op);
        return W6_L(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op,
                    uxxr, uxxr_op, uxxrl, uxxrl_op);

      // Root -> Right -> Right -> Right
      } else {
        assert(uxxrl->GetWeight() > 0);
        return PUSH_L(ux, ux_op, uxx, uxx_op,
                      uxxl, uxxl_op, uxxr, uxxr_op);
      }
    }

  // Root -> Left
  } else {
    assert(uxxr->GetWeight() > 1);
    // Protect node 'uxxr'
    PROTECT_NODE_WITH_LLX(HIDX_UXXR, uxxr, uxxr_op);
    return W7(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op, uxxr, uxxr_op);
  }
}

template<typename Key, typename Value, typename Compare, typename ValuePool>
embb_errors_t ChromaticTree<Key, Value, Compare, ValuePool>::
OverweightRight(HazardNodePtr& u, HazardOperationPtr& u_op,
                HazardNodePtr& ux, HazardOperationPtr& ux_op,
                HazardNodePtr& uxx, HazardOperationPtr& uxx_op,
                HazardNodePtr& uxl, HazardNodePtr& uxr,
                HazardNodePtr& uxxl, HazardNodePtr& uxxr,
                HazardOperationPtr& uxxr_op, bool uxx_is_right) {
  // Let "Root" be the top of the overweight violation decision tree (see p.30)
  // Root -> Middle
  if (uxxl->GetWeight() == 0) {
    // Root -> Middle -> Left
    if (uxx->GetWeight() == 0) {
      // Root -> Middle -> Left -> Left
      if (uxx_is_right) {
        // Root -> Middle -> Left -> Left -> Left
        if (uxl->GetWeight() == 0) {
          // Protect node 'uxl'
          PROTECT_NODE_WITH_LLX(HIDX_UXL, uxl, uxl_op);
          return BLK(u, u_op, ux, ux_op, uxl, uxl_op, uxx, uxx_op);

        // Root -> Middle -> Left -> Left -> Right
        } else {
          assert(uxl->GetWeight() > 0);
          // Protect node 'uxxl'
          PROTECT_NODE_WITH_LLX(HIDX_UXXL, uxxl, uxxl_op);
          return RB2_R(u, u_op, ux, ux_op, uxx, uxx_op, uxxl, uxxl_op);
        }

      // Root -> Middle -> Left -> Right
      } else {
        assert(!uxx_is_right);
        // Root -> Middle -> Left -> Right -> Left
        if (uxr->GetWeight() == 0) {
          // Protect node 'uxr'
          PROTECT_NODE_WITH_LLX(HIDX_UXR, uxr, uxr_op);
          return BLK(u, u_op, ux, ux_op, uxx, uxx_op, uxr, uxr_op);

        // Root -> Middle -> Left -> Right -> Right
        } else {
          assert(uxr->GetWeight() > 0);
          return RB1_L(u, u_op, ux, ux_op, uxx, uxx_op);
        }
      }

    // Root -> Middle -> Right
    } else {
      assert(uxx->GetWeight() > 0);
      // Protect node 'uxxl'
      PROTECT_NODE_WITH_LLX(HIDX_UXXL, uxxl, uxxl_op);

      // Get left child of 'uxxl'
      // Note: we know that 'uxxl' is not a leaf because it has weight 0.
      DEFINE_HAZARDOUS_NODE(HIDX_UXXLR, uxxlr, uxxl, GetRight);

      // Protect node 'uxxlr'
      PROTECT_NODE_WITH_LLX(HIDX_UXXLR, uxxlr, uxxlr_op);

      // Root -> Middle -> Right -> Left
      if (uxxlr->GetWeight() == 0) {
        return RB2_L(ux, ux_op, uxx, uxx_op,
                     uxxl, uxxl_op, uxxlr, uxxlr_op);

      // Root -> Middle -> Right -> Middle
      } else if (uxxlr->GetWeight() == 1) {
        DEFINE_HAZARDOUS_NODE(HIDX_UXXLRL, uxxlrl, uxxlr, GetLeft);
        if (uxxlrl == NULL) return EMBB_BUSY;

        // Root -> Middle -> Right -> Middle -> Left
        if (uxxlrl->GetWeight() == 0) {
          // Protect node 'uxxlrl'
          PROTECT_NODE_WITH_LLX(HIDX_UXXLRL, uxxlrl, uxxlrl_op);
          return W4_R(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op,
                      uxxr, uxxr_op, uxxlr, uxxlr_op, uxxlrl, uxxlrl_op);

        // Root -> Middle -> Right -> Middle -> Right
        } else {
          assert(uxxlrl->GetWeight() > 0);
          // Root -> Middle -> Right -> Middle -> Right -> Left
          // Node: reusing hazard of node 'uxxlrl' as it is no longer used
          DEFINE_HAZARDOUS_NODE(HIDX_UXXLRR, uxxlrr, uxxlr, GetRight);
          if (uxxlrr->GetWeight() == 0) {
            // Protect node 'uxxlrr'
            PROTECT_NODE_WITH_LLX(HIDX_UXXLRR, uxxlrr, uxxlrr_op);
            return W3_R(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op, uxxr,
                        uxxr_op, uxxlr, uxxlr_op, uxxlrr, uxxlrr_op);

          // Root -> Middle -> Right -> Middle -> Right -> Right
          } else {
            assert(uxxlrr->GetWeight() > 0);
            return W2_R(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op,
                        uxxr, uxxr_op, uxxlr, uxxlr_op);
          }
        }

      // Root -> Middle -> Right -> Right
      } else {
        assert(uxxlr->GetWeight() > 1);
        return W1_R(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op,
                    uxxr, uxxr_op, uxxlr, uxxlr_op);
      }
    }

  // Root -> Right
  } else if (uxxl->GetWeight() == 1) {
    // Protect node 'uxxl'
    PROTECT_NODE_WITH_LLX(HIDX_UXXL, uxxl, uxxl_op);
    // Get children of 'uxxl'
    DEFINE_HAZARDOUS_NODE(HIDX_UXXLL, uxxll, uxxl, GetLeft);
    DEFINE_HAZARDOUS_NODE(HIDX_UXXLR, uxxlr, uxxl, GetRight);
    if (uxxll == NULL) return EMBB_BUSY;

    // Root -> Right -> Left
    if (uxxll->GetWeight() == 0) {
      // Protect node 'uxxll'
      PROTECT_NODE_WITH_LLX(HIDX_UXXLL, uxxll, uxxll_op);
      return W5_R(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op,
                  uxxr, uxxr_op, uxxll, uxxll_op);

    // Root -> Right -> Right
    } else {
      assert(uxxll->GetWeight() > 0);
      // Root -> Right -> Right -> Left
      if (uxxlr->GetWeight() == 0) {
        // Protect node 'uxxlr'
        PROTECT_NODE_WITH_LLX(HIDX_UXXLR, uxxlr, uxxlr_op);
        return W6_R(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op,
                    uxxr, uxxr_op, uxxlr, uxxlr_op);

      // Root -> Right -> Right -> Right
      } else {
        assert(uxxlr->GetWeight() > 0);
        return PUSH_R(ux, ux_op, uxx, uxx_op,
                      uxxl, uxxl_op, uxxr, uxxr_op);
      }
    }

  // Root -> Left
  } else {
    assert(uxxl->GetWeight() > 1);
    // Protect node 'uxxl'
    PROTECT_NODE_WITH_LLX(HIDX_UXXL, uxxl, uxxl_op);
    return W7(ux, ux_op, uxx, uxx_op, uxxl, uxxl_op, uxxr, uxxr_op);
  }
}

} // namespace containers
} // namespace embb

#endif // EMBB_CONTAINERS_INTERNAL_LOCK_FREE_CHROMATIC_TREE_INL_H_