--- /dev/null	2019-01-28 17:47:05.000000000 +0800
+++ new/src/share/vm/jfr/recorder/checkpoint/constant/jfrThreadGroup.cpp	2019-01-28 17:47:05.000000000 +0800
@@ -0,0 +1,418 @@
+/*
+ * Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "jfr/recorder/checkpoint/jfrCheckpointWriter.hpp"
+#include "jfr/recorder/checkpoint/constant/jfrThreadGroup.hpp"
+#include "jfr/utilities/jfrResourceManager.hpp"
+#include "runtime/handles.inline.hpp"
+#include "runtime/jniHandles.hpp"
+#include "runtime/safepoint.hpp"
+#include "runtime/semaphore.hpp"
+// to get CONTENT_TYPE defines
+#include "tracefiles/traceTypes.hpp"
+#include "utilities/growableArray.hpp"
+
+class ThreadGroupExclusiveAccess : public StackObj {
+ private:
+  static Semaphore _mutex_semaphore;
+ public:
+  ThreadGroupExclusiveAccess() { _mutex_semaphore.wait(); }
+  ~ThreadGroupExclusiveAccess() { _mutex_semaphore.signal(); }
+};
+
+Semaphore ThreadGroupExclusiveAccess::_mutex_semaphore(1);
+JfrThreadGroup* JfrThreadGroup::_instance = NULL;
+
+class JfrThreadGroupPointers : public ResourceObj {
+ private:
+  const Handle _thread_group_handle;
+  jweak _thread_group_weak_ref;
+ public:
+  JfrThreadGroupPointers(Handle thread_group_handle, jweak thread_group_weak_ref);
+  Handle thread_group_handle() const;
+  jweak thread_group_weak_ref() const;
+  oopDesc* const thread_group_oop() const;
+  jweak transfer_weak_global_handle_ownership();
+  void clear_weak_ref();
+};
+
+JfrThreadGroupPointers::JfrThreadGroupPointers(Handle thread_group_handle, jweak thread_group_weak_ref) :
+  _thread_group_handle(thread_group_handle),
+  _thread_group_weak_ref(thread_group_weak_ref) {}
+
+Handle JfrThreadGroupPointers::thread_group_handle() const {
+  return _thread_group_handle;
+}
+
+jweak JfrThreadGroupPointers::thread_group_weak_ref() const {
+  return _thread_group_weak_ref;
+}
+
+oopDesc* const JfrThreadGroupPointers::thread_group_oop() const {
+  assert(_thread_group_weak_ref == NULL ||
+         JNIHandles::resolve_non_null(_thread_group_weak_ref) == _thread_group_handle(), "invariant");
+  return _thread_group_handle();
+}
+
+jweak JfrThreadGroupPointers::transfer_weak_global_handle_ownership() {
+  jweak temp = _thread_group_weak_ref;
+  _thread_group_weak_ref = NULL;
+  return temp;
+}
+
+void JfrThreadGroupPointers::clear_weak_ref() {
+  if (NULL != _thread_group_weak_ref) {
+    JNIHandles::destroy_weak_global(_thread_group_weak_ref);
+  }
+}
+
+class JfrThreadGroupsHelper : public ResourceObj {
+ private:
+  static const int invalid_iterator_pos = -1;
+  GrowableArray<JfrThreadGroupPointers*>* _thread_group_hierarchy;
+  int _current_iterator_pos;
+
+  int populate_thread_group_hierarchy(const JavaThread* jt, Thread* current);
+  JfrThreadGroupPointers& at(int index);
+
+ public:
+  JfrThreadGroupsHelper(const JavaThread* jt, Thread* current);
+  ~JfrThreadGroupsHelper();
+  JfrThreadGroupPointers& next();
+  bool is_valid() const;
+  bool has_next() const;
+};
+
+JfrThreadGroupsHelper::JfrThreadGroupsHelper(const JavaThread* jt, Thread* current) {
+  _thread_group_hierarchy = new GrowableArray<JfrThreadGroupPointers*>(10, false, mtTracing);
+  _current_iterator_pos = populate_thread_group_hierarchy(jt, current) - 1;
+}
+
+JfrThreadGroupsHelper::~JfrThreadGroupsHelper() {
+  assert(_current_iterator_pos == invalid_iterator_pos, "invariant");
+  for (int i = 0; i < _thread_group_hierarchy->length(); ++i) {
+    _thread_group_hierarchy->at(i)->clear_weak_ref();
+  }
+}
+
+JfrThreadGroupPointers& JfrThreadGroupsHelper::at(int index) {
+  assert(_thread_group_hierarchy != NULL, "invariant");
+  assert(index > invalid_iterator_pos && index < _thread_group_hierarchy->length(), "invariant");
+  return *(_thread_group_hierarchy->at(index));
+}
+
+bool JfrThreadGroupsHelper::has_next() const {
+  return _current_iterator_pos > invalid_iterator_pos;
+}
+
+bool JfrThreadGroupsHelper::is_valid() const {
+  return (_thread_group_hierarchy != NULL && _thread_group_hierarchy->length() > 0);
+}
+
+JfrThreadGroupPointers& JfrThreadGroupsHelper::next() {
+  assert(is_valid(), "invariant");
+  return at(_current_iterator_pos--);
+}
+
+/*
+ * If not at a safepoint, we create global weak references for
+ * all reachable threadgroups for this thread.
+ * If we are at a safepoint, the caller is the VMThread during
+ * JFR checkpointing. It can use naked oops, because nothing
+ * will move before the list of threadgroups is cleared and
+ * mutator threads restarted. The threadgroup list is cleared
+ * later by the VMThread as one of the final steps in JFR checkpointing
+ * (not here).
+ */
+int JfrThreadGroupsHelper::populate_thread_group_hierarchy(const JavaThread* jt, Thread* current) {
+  assert(jt != NULL && jt->is_Java_thread(), "invariant");
+  assert(current != NULL, "invariant");
+  assert(_thread_group_hierarchy != NULL, "invariant");
+
+  // immediate thread group
+  Handle thread_group_handle(current, java_lang_Thread::threadGroup(jt->threadObj()));
+  if (thread_group_handle == NULL) {
+    return 0;
+  }
+
+  const bool use_weak_handles = !SafepointSynchronize::is_at_safepoint();
+  jweak thread_group_weak_ref = use_weak_handles ? JNIHandles::make_weak_global(thread_group_handle) : NULL;
+
+  JfrThreadGroupPointers* thread_group_pointers = new JfrThreadGroupPointers(thread_group_handle, thread_group_weak_ref);
+  _thread_group_hierarchy->append(thread_group_pointers);
+  // immediate parent thread group
+  oop parent_thread_group_obj = java_lang_ThreadGroup::parent(thread_group_handle());
+  Handle parent_thread_group_handle(current, parent_thread_group_obj);
+
+  // and check parents parents...
+  while (!(parent_thread_group_handle == NULL)) {
+    const jweak parent_group_weak_ref = use_weak_handles ? JNIHandles::make_weak_global(parent_thread_group_handle) : NULL;
+    thread_group_pointers = new JfrThreadGroupPointers(parent_thread_group_handle, parent_group_weak_ref);
+    _thread_group_hierarchy->append(thread_group_pointers);
+    parent_thread_group_obj = java_lang_ThreadGroup::parent(parent_thread_group_handle());
+    parent_thread_group_handle = Handle(current, parent_thread_group_obj);
+  }
+  return _thread_group_hierarchy->length();
+}
+
+static traceid next_id() {
+  static traceid _current_threadgroup_id = 0;
+  return ++_current_threadgroup_id;
+}
+
+class JfrThreadGroup::JfrThreadGroupEntry : public JfrCHeapObj {
+  friend class JfrThreadGroup;
+ private:
+  traceid _thread_group_id;
+  traceid _parent_group_id;
+  char* _thread_group_name; // utf8 format
+  // If an entry is created during a safepoint, the
+  // _thread_group_oop contains a direct oop to
+  // the java.lang.ThreadGroup object.
+  // If an entry is created on javathread exit time (not at safepoint),
+  // _thread_group_weak_ref contains a JNI weak global handle
+  // indirection to the java.lang.ThreadGroup object.
+  // Note: we cannot use a union here since CHECK_UNHANDLED_OOPS makes oop have
+  //       a ctor which isn't allowed in a union by the SunStudio compiler
+  oop _thread_group_oop;
+  jweak _thread_group_weak_ref;
+
+  JfrThreadGroupEntry(const char* tgstr, JfrThreadGroupPointers& ptrs);
+  ~JfrThreadGroupEntry();
+
+  traceid thread_group_id() const { return _thread_group_id; }
+  void set_thread_group_id(traceid tgid) { _thread_group_id = tgid; }
+
+  const char* const thread_group_name() const { return _thread_group_name; }
+  void set_thread_group_name(const char* tgname);
+
+  traceid parent_group_id() const { return _parent_group_id; }
+  void set_parent_group_id(traceid pgid) { _parent_group_id = pgid; }
+
+  void set_thread_group(JfrThreadGroupPointers& ptrs);
+  bool is_equal(const JfrThreadGroupPointers& ptrs) const;
+  const oop thread_group() const;
+};
+
+JfrThreadGroup::JfrThreadGroupEntry::JfrThreadGroupEntry(const char* tgname, JfrThreadGroupPointers& ptrs) :
+  _thread_group_id(0),
+  _parent_group_id(0),
+  _thread_group_name(NULL),
+  _thread_group_oop(NULL),
+  _thread_group_weak_ref(NULL) {
+  set_thread_group_name(tgname);
+  set_thread_group(ptrs);
+}
+
+JfrThreadGroup::JfrThreadGroupEntry::~JfrThreadGroupEntry() {
+  if (_thread_group_name != NULL) {
+    JfrCHeapObj::free(_thread_group_name, strlen(_thread_group_name) + 1);
+  }
+  if (_thread_group_weak_ref != NULL) {
+    JNIHandles::destroy_weak_global(_thread_group_weak_ref);
+  }
+}
+
+void JfrThreadGroup::JfrThreadGroupEntry::set_thread_group_name(const char* tgname) {
+  assert(_thread_group_name == NULL, "invariant");
+  if (tgname != NULL) {
+    size_t len = strlen(tgname);
+    _thread_group_name = JfrCHeapObj::new_array<char>(len+1);
+    strncpy(_thread_group_name, tgname, len);
+    _thread_group_name[len] = '\0';
+  }
+}
+
+const oop JfrThreadGroup::JfrThreadGroupEntry::thread_group() const {
+  return _thread_group_weak_ref != NULL ? JNIHandles::resolve(_thread_group_weak_ref) : _thread_group_oop;
+}
+
+void JfrThreadGroup::JfrThreadGroupEntry::set_thread_group(JfrThreadGroupPointers& ptrs) {
+  _thread_group_weak_ref = ptrs.transfer_weak_global_handle_ownership();
+  if (_thread_group_weak_ref == NULL) {
+    _thread_group_oop = ptrs.thread_group_oop();
+    assert(_thread_group_oop != NULL, "invariant");
+  } else {
+    _thread_group_oop = NULL;
+  }
+}
+
+JfrThreadGroup::JfrThreadGroup() : _list(NULL) {
+  _list = new (ResourceObj::C_HEAP, mtTracing) GrowableArray<JfrThreadGroupEntry*>(30, true);
+}
+
+JfrThreadGroup::~JfrThreadGroup() {
+  assert(SafepointSynchronize::is_at_safepoint(), "invariant");
+  if (_list != NULL) {
+    for (int i = 0; i < _list->length(); i++) {
+      JfrThreadGroupEntry* e = _list->at(i);
+      delete e;
+    }
+    delete _list;
+  }
+}
+
+JfrThreadGroup* JfrThreadGroup::instance() {
+  return _instance;
+}
+
+void JfrThreadGroup::set_instance(JfrThreadGroup* new_instance) {
+  _instance = new_instance;
+}
+
+traceid JfrThreadGroup::thread_group_id(const JavaThread* jt, Thread* current) {
+  ResourceMark rm(current);
+  HandleMark hm(current);
+  JfrThreadGroupsHelper helper(jt, current);
+  return helper.is_valid() ? thread_group_id_internal(helper) : 0;
+}
+
+traceid JfrThreadGroup::thread_group_id(JavaThread* const jt) {
+  assert(!JfrStream_lock->owned_by_self(), "holding stream lock but should not hold it here");
+  return thread_group_id(jt, jt);
+}
+
+traceid JfrThreadGroup::thread_group_id_internal(JfrThreadGroupsHelper& helper) {
+  ThreadGroupExclusiveAccess lock;
+  JfrThreadGroup* tg_instance = instance();
+  if (tg_instance == NULL) {
+    tg_instance = new JfrThreadGroup();
+    if (tg_instance == NULL) {
+      return 0;
+    }
+    set_instance(tg_instance);
+  }
+
+  JfrThreadGroupEntry* tge = NULL;
+  int parent_thread_group_id = 0;
+  while (helper.has_next()) {
+    JfrThreadGroupPointers& ptrs = helper.next();
+    tge = tg_instance->find_entry(ptrs);
+    if (NULL == tge) {
+      tge = tg_instance->new_entry(ptrs);
+      assert(tge != NULL, "invariant");
+      tge->set_parent_group_id(parent_thread_group_id);
+    }
+    parent_thread_group_id = tge->thread_group_id();
+  }
+  // the last entry in the hierarchy is the immediate thread group
+  return tge->thread_group_id();
+}
+
+bool JfrThreadGroup::JfrThreadGroupEntry::is_equal(const JfrThreadGroupPointers& ptrs) const {
+  return ptrs.thread_group_oop() == thread_group();
+}
+
+JfrThreadGroup::JfrThreadGroupEntry*
+JfrThreadGroup::find_entry(const JfrThreadGroupPointers& ptrs) const {
+  for (int index = 0; index < _list->length(); ++index) {
+    JfrThreadGroupEntry* curtge = _list->at(index);
+    if (curtge->is_equal(ptrs)) {
+      return curtge;
+    }
+  }
+  return (JfrThreadGroupEntry*) NULL;
+}
+
+// Assumes you already searched for the existence
+// of a corresponding entry in find_entry().
+JfrThreadGroup::JfrThreadGroupEntry*
+JfrThreadGroup::new_entry(JfrThreadGroupPointers& ptrs) {
+  const char* str = NULL;
+  typeArrayOop name = java_lang_ThreadGroup::name(ptrs.thread_group_oop());
+  if (name != NULL) {
+    str = UNICODE::as_utf8((jchar*) name->base(T_CHAR), name->length());
+  }
+  JfrThreadGroupEntry* const tge = new JfrThreadGroupEntry(str, ptrs);
+  add_entry(tge);
+  return tge;
+}
+
+int JfrThreadGroup::add_entry(JfrThreadGroupEntry* tge) {
+  assert(tge != NULL, "attempting to add a null entry!");
+  assert(0 == tge->thread_group_id(), "id must be unassigned!");
+  tge->set_thread_group_id(next_id());
+  return _list->append(tge);
+}
+
+void JfrThreadGroup::write_thread_group_entries(JfrCheckpointWriter& writer) const {
+  assert(_list != NULL && !_list->is_empty(), "should not need be here!");
+  const int number_of_tg_entries = _list->length();
+  writer.write_number_of_constants(number_of_tg_entries);
+  for (int index = 0; index < number_of_tg_entries; ++index) {
+    const JfrThreadGroupEntry* const curtge = _list->at(index);
+    writer.write_key(curtge->thread_group_id());
+    writer.write(curtge->parent_group_id());
+    writer.write(curtge->thread_group_name());
+  }
+}
+
+void JfrThreadGroup::write_selective_thread_group(JfrCheckpointWriter* writer, traceid thread_group_id) const {
+  assert(writer != NULL, "invariant");
+  assert(_list != NULL && !_list->is_empty(), "should not need be here!");
+  const int number_of_tg_entries = _list->length();
+
+  // save context
+  const JfrCheckpointContext ctx = writer->context();
+  writer->write_constant_type(CONSTANT_TYPE_THREADGROUP);
+  const jlong count_offset = writer->reserve(sizeof(u4)); // Don't know how many yet
+  int number_of_entries_written = 0;
+  for (int index = number_of_tg_entries - 1; index >= 0; --index) {
+    const JfrThreadGroupEntry* const curtge = _list->at(index);
+    if (thread_group_id == curtge->thread_group_id()) {
+      writer->write_key(curtge->thread_group_id());
+      writer->write(curtge->parent_group_id());
+      writer->write(curtge->thread_group_name());
+      ++number_of_entries_written;
+      thread_group_id = curtge->parent_group_id();
+    }
+  }
+  if (number_of_entries_written == 0) {
+    // nothing to write, restore context
+    writer->set_context(ctx);
+    return;
+  }
+  assert(number_of_entries_written > 0, "invariant");
+  writer->write_number_of_constants(number_of_entries_written, count_offset);
+}
+
+// Write out JfrThreadGroup instance and then delete it
+void JfrThreadGroup::write(JfrCheckpointWriter& writer) {
+  ThreadGroupExclusiveAccess lock;
+  JfrThreadGroup* tg_instance = instance();
+  assert(tg_instance != NULL, "invariant");
+  ResourceManager<JfrThreadGroup> tg_handle(tg_instance);
+  set_instance(NULL);
+  tg_handle->write_thread_group_entries(writer);
+}
+
+// for writing a particular thread group
+void JfrThreadGroup::write(JfrCheckpointWriter* writer, traceid thread_group_id) {
+  assert(writer != NULL, "invariant");
+  ThreadGroupExclusiveAccess lock;
+  JfrThreadGroup* const tg_instance = instance();
+  assert(tg_instance != NULL, "invariant");
+  tg_instance->write_selective_thread_group(writer, thread_group_id);
+}