refs #5828 destroy the root node when the concurrent tree is destroyed.

git-svn-id: file:///svn/toku/tokudb@51345 c7de825b-a66e-492c-adef-691d508d4ae1

locktree/concurrent_tree.cc

@@ -9,11 +9,11 @@
 void concurrent_tree::create(comparator *cmp) {
     // start with an empty root node. we do this instead of
     // setting m_root to null so there's always a root to lock
-    m_root.init_root(cmp);
+    m_root.create_root(cmp);
 }
 
 void concurrent_tree::destroy(void) {
-    invariant(is_empty());
+    m_root.destroy_root();
 }
 
 bool concurrent_tree::is_empty(void) {

locktree/treenode.cc

@@ -32,11 +32,18 @@ void treenode::init(comparator *cmp) {
     m_right_child.set(nullptr);
 }
 
-void treenode::init_root(comparator *cmp) {
+void treenode::create_root(comparator *cmp) {
     init(cmp);
     m_is_root = true;
 }
 
+void treenode::destroy_root(void) {
+    invariant(is_root());
+    invariant(is_empty());
+    toku_mutex_destroy(&m_mutex);
+    m_cmp = nullptr;
+}
+
 void treenode::set_range_and_txnid(const keyrange &range, TXNID txnid) {
     // allocates a new copy of the range for this node
     m_range.create_copy(range);

locktree/treenode.h

@@ -24,7 +24,7 @@ namespace toku {
 // - left and right children may be null
 //
 // to build a tree on top of this abstraction, the user:
-// - provides memory for a root node, initializes it via init_root()
+// - provides memory for a root node, initializes it via create_root()
 // - performs tree operations on the root node. memory management
 //   below the root node is handled by the abstraction, not the user.
 // this pattern:
@@ -38,8 +38,11 @@ public:
     // - node is locked and children are never locked
     // - node may be unlocked if no other thread has visibility
 
-    // effect: initialize a treenode, marks it as the root
-    void init_root(comparator *cmp);
+    // effect: create the root node
+    void create_root(comparator *cmp);
+
+    // effect: destroys the root node
+    void destroy_root(void);
 
     // effect: sets the txnid and copies the given range for this node
     void set_range_and_txnid(const keyrange &range, TXNID txnid);