8364258: ThreadGroup constant pool serialization is not normalized

Reviewed-by: egahlin
Backport-of: 3bc449797eb59f9770d2a06d260b23b6efd5ff0f

Author: Markus Grönlund

src/hotspot/share/jfr/recorder/checkpoint/types/jfrThreadGroup.cpp

@@ -0,0 +1,331 @@
+/*
+ * Copyright (c) 2016, 2025, 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 "jfr/jni/jfrJavaSupport.hpp"
+#include "jfr/recorder/checkpoint/jfrCheckpointWriter.hpp"
+#include "jfr/recorder/checkpoint/types/jfrThreadGroupManager.hpp"
+#include "jfr/recorder/checkpoint/types/traceid/jfrTraceIdEpoch.hpp"
+#include "jfr/utilities/jfrAllocation.hpp"
+#include "jfr/utilities/jfrLinkedList.inline.hpp"
+#include "memory/resourceArea.hpp"
+#include "runtime/handles.inline.hpp"
+#include "runtime/jniHandles.inline.hpp"
+#include "runtime/safepoint.hpp"
+#include "runtime/semaphore.hpp"
+#include "runtime/thread.inline.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);
+
+static traceid next_id() {
+  static traceid _tgid = 1; // 1 is reserved for thread group "VirtualThreads"
+  return ++_tgid;
+}
+
+class JfrThreadGroup : public JfrCHeapObj {
+  template <typename, typename>
+  friend class JfrLinkedList;
+ private:
+  mutable const JfrThreadGroup* _next;
+  const JfrThreadGroup* _parent;
+  traceid _tgid;
+  char* _tg_name; // utf8 format
+  jweak _tg_handle;
+  mutable u2 _generation;
+
+ public:
+  JfrThreadGroup(Handle tg, const JfrThreadGroup* parent) :
+    _next(nullptr), _parent(parent), _tgid(next_id()), _tg_name(nullptr),
+    _tg_handle(JNIHandles::make_weak_global(tg)), _generation(0) {
+    const char* name = java_lang_ThreadGroup::name(tg());
+    if (name != nullptr) {
+      const size_t len = strlen(name);
+      _tg_name = JfrCHeapObj::new_array<char>(len + 1);
+      strncpy(_tg_name, name, len + 1);
+    }
+  }
+
+  ~JfrThreadGroup() {
+    JNIHandles::destroy_weak_global(_tg_handle);
+    if (_tg_name != nullptr) {
+      JfrCHeapObj::free(_tg_name, strlen(_tg_name) + 1);
+    }
+  }
+
+  const JfrThreadGroup* next() const { return _next; }
+
+  traceid id() const { return _tgid; }
+
+  const char* name() const {
+    return _tg_name;
+  }
+
+  const JfrThreadGroup* parent() const { return _parent; }
+
+  traceid parent_id() const {
+    return _parent != nullptr ? _parent->id() : 0;
+  }
+
+  bool is_dead() const {
+    return JNIHandles::resolve(_tg_handle) == nullptr;
+  }
+
+  bool operator==(oop tg) const {
+    assert(tg != nullptr, "invariant");
+    return tg == JNIHandles::resolve(_tg_handle);
+  }
+
+  bool should_write() const {
+    return !JfrTraceIdEpoch::is_current_epoch_generation(_generation);
+  }
+
+  void set_written() const {
+    assert(should_write(), "invariant");
+    _generation = JfrTraceIdEpoch::epoch_generation();
+  }
+};
+
+typedef JfrLinkedList<const JfrThreadGroup> JfrThreadGroupList;
+
+static JfrThreadGroupList* _list = nullptr;
+
+static JfrThreadGroupList& list() {
+  assert(_list != nullptr, "invariant");
+  return *_list;
+}
+
+bool JfrThreadGroupManager::create() {
+  assert(_list == nullptr, "invariant");
+  _list = new JfrThreadGroupList();
+  return _list != nullptr;
+}
+
+void JfrThreadGroupManager::destroy() {
+  delete _list;
+  _list = nullptr;
+}
+
+static int populate(GrowableArray<Handle>* hierarchy, const JavaThread* jt, Thread* current) {
+  assert(hierarchy != nullptr, "invariant");
+  assert(jt != nullptr, "invariant");
+  assert(current == Thread::current(), "invariant");
+
+  oop thread_oop = jt->threadObj();
+  if (thread_oop == nullptr) {
+    return 0;
+  }
+  // Immediate thread group.
+  const Handle tg_handle(current, java_lang_Thread::threadGroup(thread_oop));
+  if (tg_handle.is_null()) {
+    return 0;
+  }
+  hierarchy->append(tg_handle);
+
+  // Thread group parent and then its parents...
+  Handle parent_tg_handle(current, java_lang_ThreadGroup::parent(tg_handle()));
+
+  while (parent_tg_handle != nullptr) {
+    hierarchy->append(parent_tg_handle);
+    parent_tg_handle = Handle(current, java_lang_ThreadGroup::parent(parent_tg_handle()));
+  }
+
+  return hierarchy->length();
+}
+
+class JfrThreadGroupLookup : public ResourceObj {
+  static const int invalid_iterator = -1;
+ private:
+  GrowableArray<Handle>* _hierarchy;
+  mutable int _iterator;
+
+ public:
+  JfrThreadGroupLookup(const JavaThread* jt, Thread* current) :
+    _hierarchy(new GrowableArray<Handle>(16)),
+    _iterator(populate(_hierarchy, jt, current) - 1) {}
+
+  bool has_next() const {
+    return _iterator > invalid_iterator;
+  }
+
+  const Handle& next() const {
+    assert(has_next(), "invariant");
+    return _hierarchy->at(_iterator--);
+  }
+};
+
+static const JfrThreadGroup* find_or_add(const Handle& tg_oop, const JfrThreadGroup* parent) {
+  assert(parent == nullptr || list().in_list(parent), "invariant");
+  const JfrThreadGroup* tg = list().head();
+  const JfrThreadGroup* result = nullptr;
+  while (tg != nullptr) {
+    if (*tg == tg_oop()) {
+      assert(tg->parent() == parent, "invariant");
+      result = tg;
+      tg = nullptr;
+      continue;
+    }
+    tg = tg->next();
+  }
+  if (result == nullptr) {
+    result = new JfrThreadGroup(tg_oop, parent);
+    list().add(result);
+  }
+  return result;
+}
+
+static traceid find_tgid(const JfrThreadGroupLookup& lookup) {
+  const JfrThreadGroup* tg = nullptr;
+  const JfrThreadGroup* ptg = nullptr;
+  while (lookup.has_next()) {
+    tg = find_or_add(lookup.next(), ptg);
+    ptg = tg;
+  }
+  return tg != nullptr ? tg->id() : 0;
+}
+
+static traceid find(const JfrThreadGroupLookup& lookup) {
+  ThreadGroupExclusiveAccess lock;
+  return find_tgid(lookup);
+}
+
+traceid JfrThreadGroupManager::thread_group_id(JavaThread* jt) {
+  DEBUG_ONLY(JfrJavaSupport::check_java_thread_in_vm(jt);)
+  ResourceMark rm(jt);
+  HandleMark hm(jt);
+  const JfrThreadGroupLookup lookup(jt, jt);
+  return find(lookup);
+}
+
+traceid JfrThreadGroupManager::thread_group_id(const JavaThread* jt, Thread* current) {
+  assert(jt != nullptr, "invariant");
+  assert(current != nullptr, "invariant");
+  assert(!current->is_Java_thread() || JavaThread::cast(current)->thread_state() == _thread_in_vm, "invariant");
+  ResourceMark rm(current);
+  HandleMark hm(current);
+  const JfrThreadGroupLookup lookup(jt, current);
+  return find(lookup);
+}
+
+static void write_virtual_thread_group(JfrCheckpointWriter& writer) {
+  writer.write_key(1);      // 1 is reserved for VirtualThread group
+  writer.write<traceid>(0); // parent
+  const oop vgroup = java_lang_Thread_Constants::get_VTHREAD_GROUP();
+  assert(vgroup != (oop)nullptr, "invariant");
+  const char* const vgroup_name = java_lang_ThreadGroup::name(vgroup);
+  assert(vgroup_name != nullptr, "invariant");
+  writer.write(vgroup_name);
+}
+
+static int write_thread_group(JfrCheckpointWriter& writer, const JfrThreadGroup* tg, bool to_blob = false) {
+  assert(tg != nullptr, "invariant");
+  if (tg->should_write() || to_blob) {
+    writer.write_key(tg->id());
+    writer.write(tg->parent_id());
+    writer.write(tg->name());
+    if (!to_blob) {
+      tg->set_written();
+    }
+    return 1;
+  }
+  return 0;
+}
+
+// For writing all live thread groups while removing and deleting dead thread groups.
+void JfrThreadGroupManager::serialize(JfrCheckpointWriter& writer) {
+  DEBUG_ONLY(JfrJavaSupport::check_java_thread_in_vm(JavaThread::current());)
+
+  const uint64_t count_offset = writer.reserve(sizeof(u4)); // Don't know how many yet
+
+  // First write the pre-defined ThreadGroup for virtual threads.
+  write_virtual_thread_group(writer);
+  int number_of_groups_written = 1;
+
+  const JfrThreadGroup* next = nullptr;
+  const JfrThreadGroup* prev = nullptr;
+
+  {
+    ThreadGroupExclusiveAccess lock;
+    const JfrThreadGroup* tg = list().head();
+    while (tg != nullptr) {
+      next = tg->next();
+      if (tg->is_dead()) {
+        prev = list().excise(prev, tg);
+        assert(!list().in_list(tg), "invariant");
+        delete tg;
+        tg = next;
+        continue;
+      }
+      number_of_groups_written += write_thread_group(writer, tg);
+      prev = tg;
+      tg = next;
+    }
+  }
+
+  assert(number_of_groups_written > 0, "invariant");
+  writer.write_count(number_of_groups_written, count_offset);
+}
+
+// For writing a specific thread group and its ancestry.
+void JfrThreadGroupManager::serialize(JfrCheckpointWriter& writer, traceid tgid, bool to_blob) {
+  DEBUG_ONLY(JfrJavaSupport::check_java_thread_in_vm(JavaThread::current());)
+  // save context
+  const JfrCheckpointContext ctx = writer.context();
+
+  writer.write_type(TYPE_THREADGROUP);
+  const uint64_t count_offset = writer.reserve(sizeof(u4)); // Don't know how many yet
+
+  int number_of_groups_written = 0;
+
+  {
+    ThreadGroupExclusiveAccess lock;
+    const JfrThreadGroup* tg = list().head();
+    while (tg != nullptr) {
+      if (tgid == tg->id()) {
+        while (tg != nullptr) {
+          number_of_groups_written += write_thread_group(writer, tg, to_blob);
+          tg = tg->parent();
+        }
+        break;
+      }
+      tg = tg->next();
+    }
+  }
+
+  if (number_of_groups_written == 0) {
+    // nothing to write, restore context
+    writer.set_context(ctx);
+    return;
+  }
+
+  assert(number_of_groups_written > 0, "invariant");
+  writer.write_count(number_of_groups_written, count_offset);
+}

src/hotspot/share/jfr/recorder/checkpoint/types/jfrThreadGroupManager.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016, 2025, 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
@@ -22,44 +22,27 @@
  *
  */
 
-#ifndef SHARE_JFR_RECORDER_CHECKPOINT_TYPES_JFRTHREADGROUP_HPP
-#define SHARE_JFR_RECORDER_CHECKPOINT_TYPES_JFRTHREADGROUP_HPP
+#ifndef SHARE_JFR_RECORDER_CHECKPOINT_TYPES_JFRTHREADGROUPMANAGER_HPP
+#define SHARE_JFR_RECORDER_CHECKPOINT_TYPES_JFRTHREADGROUPMANAGER_HPP
 
-#include "jfr/utilities/jfrAllocation.hpp"
 #include "jfr/utilities/jfrTypes.hpp"
-#include "jni.h"
+#include "memory/allStatic.hpp"
 
 class JfrCheckpointWriter;
-template <typename>
-class GrowableArray;
-class JfrThreadGroupsHelper;
-class JfrThreadGroupPointers;
 
-class JfrThreadGroup : public JfrCHeapObj {
-  friend class JfrCheckpointThreadClosure;
- private:
-  static JfrThreadGroup* _instance;
-  class JfrThreadGroupEntry;
-  GrowableArray<JfrThreadGroupEntry*>* _list;
-
-  JfrThreadGroup();
-  JfrThreadGroupEntry* find_entry(const JfrThreadGroupPointers& ptrs) const;
-  JfrThreadGroupEntry* new_entry(JfrThreadGroupPointers& ptrs);
-  int add_entry(JfrThreadGroupEntry* const tge);
-
-  void write_thread_group_entries(JfrCheckpointWriter& writer) const;
-  void write_selective_thread_group(JfrCheckpointWriter* writer, traceid thread_group_id) const;
+class JfrThreadGroupManager : public AllStatic {
+  friend class JfrRecorder;
 
-  static traceid thread_group_id_internal(JfrThreadGroupsHelper& helper);
-  static JfrThreadGroup* instance();
-  static void set_instance(JfrThreadGroup* new_instance);
+ private:
+  static bool create();
+  static void destroy();
 
  public:
-  ~JfrThreadGroup();
   static void serialize(JfrCheckpointWriter& w);
-  static void serialize(JfrCheckpointWriter* w, traceid thread_group_id);
+  static void serialize(JfrCheckpointWriter& w, traceid tgid, bool is_blob);
+
   static traceid thread_group_id(JavaThread* thread);
   static traceid thread_group_id(const JavaThread* thread, Thread* current);
 };
 
-#endif // SHARE_JFR_RECORDER_CHECKPOINT_TYPES_JFRTHREADGROUP_HPP
+#endif // SHARE_JFR_RECORDER_CHECKPOINT_TYPES_JFRTHREADGROUPMANAGER_HPP