hotspot/src/share/vm/prims/jvmtiEnvBase.cpp
changeset 1 489c9b5090e2
child 1403 3be05c51cf44
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/prims/jvmtiEnvBase.cpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,1415 @@
+/*
+ * Copyright 2003-2007 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+# include "incls/_precompiled.incl"
+# include "incls/_jvmtiEnvBase.cpp.incl"
+
+
+///////////////////////////////////////////////////////////////
+//
+// JvmtiEnvBase
+//
+
+JvmtiEnvBase* JvmtiEnvBase::_head_environment = NULL;
+
+bool JvmtiEnvBase::_globally_initialized = false;
+volatile bool JvmtiEnvBase::_needs_clean_up = false;
+
+jvmtiPhase JvmtiEnvBase::_phase = JVMTI_PHASE_PRIMORDIAL;
+
+volatile int JvmtiEnvBase::_dying_thread_env_iteration_count = 0;
+
+extern jvmtiInterface_1_ jvmti_Interface;
+extern jvmtiInterface_1_ jvmtiTrace_Interface;
+
+
+// perform initializations that must occur before any JVMTI environments
+// are released but which should only be initialized once (no matter
+// how many environments are created).
+void
+JvmtiEnvBase::globally_initialize() {
+  assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(), "sanity check");
+  assert(_globally_initialized == false, "bad call");
+
+  JvmtiManageCapabilities::initialize();
+
+#ifndef JVMTI_KERNEL
+  // register extension functions and events
+  JvmtiExtensions::register_extensions();
+#endif // !JVMTI_KERNEL
+
+#ifdef JVMTI_TRACE
+  JvmtiTrace::initialize();
+#endif
+
+  _globally_initialized = true;
+}
+
+
+void
+JvmtiEnvBase::initialize() {
+  assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(), "sanity check");
+
+  // Add this environment to the end of the environment list (order is important)
+  {
+    // This block of code must not contain any safepoints, as list deallocation
+    // (which occurs at a safepoint) cannot occur simultaneously with this list
+    // addition.  Note: No_Safepoint_Verifier cannot, currently, be used before
+    // threads exist.
+    JvmtiEnvIterator it;
+    JvmtiEnvBase *previous_env = NULL;
+    for (JvmtiEnvBase* env = it.first(); env != NULL; env = it.next(env)) {
+      previous_env = env;
+    }
+    if (previous_env == NULL) {
+      _head_environment = this;
+    } else {
+      previous_env->set_next_environment(this);
+    }
+  }
+
+  if (_globally_initialized == false) {
+    globally_initialize();
+  }
+}
+
+
+JvmtiEnvBase::JvmtiEnvBase() : _env_event_enable() {
+  _env_local_storage = NULL;
+  _tag_map = NULL;
+  _native_method_prefix_count = 0;
+  _native_method_prefixes = NULL;
+  _next = NULL;
+  _class_file_load_hook_ever_enabled = false;
+
+  // Moot since ClassFileLoadHook not yet enabled.
+  // But "true" will give a more predictable ClassFileLoadHook behavior
+  // for environment creation during ClassFileLoadHook.
+  _is_retransformable = true;
+
+  // all callbacks initially NULL
+  memset(&_event_callbacks,0,sizeof(jvmtiEventCallbacks));
+
+  // all capabilities initially off
+  memset(&_current_capabilities, 0, sizeof(_current_capabilities));
+
+  // all prohibited capabilities initially off
+  memset(&_prohibited_capabilities, 0, sizeof(_prohibited_capabilities));
+
+  _magic = JVMTI_MAGIC;
+
+  JvmtiEventController::env_initialize((JvmtiEnv*)this);
+
+#ifdef JVMTI_TRACE
+  _jvmti_external.functions = strlen(TraceJVMTI)? &jvmtiTrace_Interface : &jvmti_Interface;
+#else
+  _jvmti_external.functions = &jvmti_Interface;
+#endif
+}
+
+
+void
+JvmtiEnvBase::dispose() {
+
+#ifdef JVMTI_TRACE
+  JvmtiTrace::shutdown();
+#endif
+
+  // Dispose of event info and let the event controller call us back
+  // in a locked state (env_dispose, below)
+  JvmtiEventController::env_dispose(this);
+}
+
+void
+JvmtiEnvBase::env_dispose() {
+  assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(), "sanity check");
+
+  // We have been entered with all events disabled on this environment.
+  // A race to re-enable events (by setting callbacks) is prevented by
+  // checking for a valid environment when setting callbacks (while
+  // holding the JvmtiThreadState_lock).
+
+  // Mark as invalid.
+  _magic = DISPOSED_MAGIC;
+
+  // Relinquish all capabilities.
+  jvmtiCapabilities *caps = get_capabilities();
+  JvmtiManageCapabilities::relinquish_capabilities(caps, caps, caps);
+
+  // Same situation as with events (see above)
+  set_native_method_prefixes(0, NULL);
+
+#ifndef JVMTI_KERNEL
+  JvmtiTagMap* tag_map_to_deallocate = _tag_map;
+  set_tag_map(NULL);
+  // A tag map can be big, deallocate it now
+  if (tag_map_to_deallocate != NULL) {
+    delete tag_map_to_deallocate;
+  }
+#endif // !JVMTI_KERNEL
+
+  _needs_clean_up = true;
+}
+
+
+JvmtiEnvBase::~JvmtiEnvBase() {
+  assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
+
+  // There is a small window of time during which the tag map of a
+  // disposed environment could have been reallocated.
+  // Make sure it is gone.
+#ifndef JVMTI_KERNEL
+  JvmtiTagMap* tag_map_to_deallocate = _tag_map;
+  set_tag_map(NULL);
+  // A tag map can be big, deallocate it now
+  if (tag_map_to_deallocate != NULL) {
+    delete tag_map_to_deallocate;
+  }
+#endif // !JVMTI_KERNEL
+
+  _magic = BAD_MAGIC;
+}
+
+
+void
+JvmtiEnvBase::periodic_clean_up() {
+  assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
+
+  // JvmtiEnvBase reference is saved in JvmtiEnvThreadState. So
+  // clean up JvmtiThreadState before deleting JvmtiEnv pointer.
+  JvmtiThreadState::periodic_clean_up();
+
+  // Unlink all invalid environments from the list of environments
+  // and deallocate them
+  JvmtiEnvIterator it;
+  JvmtiEnvBase* previous_env = NULL;
+  JvmtiEnvBase* env = it.first();
+  while (env != NULL) {
+    if (env->is_valid()) {
+      previous_env = env;
+      env = it.next(env);
+    } else {
+      // This one isn't valid, remove it from the list and deallocate it
+      JvmtiEnvBase* defunct_env = env;
+      env = it.next(env);
+      if (previous_env == NULL) {
+        _head_environment = env;
+      } else {
+        previous_env->set_next_environment(env);
+      }
+      delete defunct_env;
+    }
+  }
+
+}
+
+
+void
+JvmtiEnvBase::check_for_periodic_clean_up() {
+  assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
+
+  class ThreadInsideIterationClosure: public ThreadClosure {
+   private:
+    bool _inside;
+   public:
+    ThreadInsideIterationClosure() : _inside(false) {};
+
+    void do_thread(Thread* thread) {
+      _inside |= thread->is_inside_jvmti_env_iteration();
+    }
+
+    bool is_inside_jvmti_env_iteration() {
+      return _inside;
+    }
+  };
+
+  if (_needs_clean_up) {
+    // Check if we are currently iterating environment,
+    // deallocation should not occur if we are
+    ThreadInsideIterationClosure tiic;
+    Threads::threads_do(&tiic);
+    if (!tiic.is_inside_jvmti_env_iteration() &&
+             !is_inside_dying_thread_env_iteration()) {
+      _needs_clean_up = false;
+      JvmtiEnvBase::periodic_clean_up();
+    }
+  }
+}
+
+
+void
+JvmtiEnvBase::record_first_time_class_file_load_hook_enabled() {
+  assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(),
+         "sanity check");
+
+  if (!_class_file_load_hook_ever_enabled) {
+    _class_file_load_hook_ever_enabled = true;
+
+    if (get_capabilities()->can_retransform_classes) {
+      _is_retransformable = true;
+    } else {
+      _is_retransformable = false;
+
+      // cannot add retransform capability after ClassFileLoadHook has been enabled
+      get_prohibited_capabilities()->can_retransform_classes = 1;
+    }
+  }
+}
+
+
+void
+JvmtiEnvBase::record_class_file_load_hook_enabled() {
+  if (!_class_file_load_hook_ever_enabled) {
+    if (Threads::number_of_threads() == 0) {
+      record_first_time_class_file_load_hook_enabled();
+    } else {
+      MutexLocker mu(JvmtiThreadState_lock);
+      record_first_time_class_file_load_hook_enabled();
+    }
+  }
+}
+
+
+jvmtiError
+JvmtiEnvBase::set_native_method_prefixes(jint prefix_count, char** prefixes) {
+  assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(),
+         "sanity check");
+
+  int old_prefix_count = get_native_method_prefix_count();
+  char **old_prefixes = get_native_method_prefixes();
+
+  // allocate and install the new prefixex
+  if (prefix_count == 0 || !is_valid()) {
+    _native_method_prefix_count = 0;
+    _native_method_prefixes = NULL;
+  } else {
+    // there are prefixes, allocate an array to hold them, and fill it
+    char** new_prefixes = (char**)os::malloc((prefix_count) * sizeof(char*));
+    if (new_prefixes == NULL) {
+      return JVMTI_ERROR_OUT_OF_MEMORY;
+    }
+    for (int i = 0; i < prefix_count; i++) {
+      char* prefix = prefixes[i];
+      if (prefix == NULL) {
+        for (int j = 0; j < (i-1); j++) {
+          os::free(new_prefixes[j]);
+        }
+        os::free(new_prefixes);
+        return JVMTI_ERROR_NULL_POINTER;
+      }
+      prefix = os::strdup(prefixes[i]);
+      if (prefix == NULL) {
+        for (int j = 0; j < (i-1); j++) {
+          os::free(new_prefixes[j]);
+        }
+        os::free(new_prefixes);
+        return JVMTI_ERROR_OUT_OF_MEMORY;
+      }
+      new_prefixes[i] = prefix;
+    }
+    _native_method_prefix_count = prefix_count;
+    _native_method_prefixes = new_prefixes;
+  }
+
+  // now that we know the new prefixes have been successfully installed we can
+  // safely remove the old ones
+  if (old_prefix_count != 0) {
+    for (int i = 0; i < old_prefix_count; i++) {
+      os::free(old_prefixes[i]);
+    }
+    os::free(old_prefixes);
+  }
+
+  return JVMTI_ERROR_NONE;
+}
+
+
+// Collect all the prefixes which have been set in any JVM TI environments
+// by the SetNativeMethodPrefix(es) functions.  Be sure to maintain the
+// order of environments and the order of prefixes within each environment.
+// Return in a resource allocated array.
+char**
+JvmtiEnvBase::get_all_native_method_prefixes(int* count_ptr) {
+  assert(Threads::number_of_threads() == 0 ||
+         SafepointSynchronize::is_at_safepoint() ||
+         JvmtiThreadState_lock->is_locked(),
+         "sanity check");
+
+  int total_count = 0;
+  GrowableArray<char*>* prefix_array =new GrowableArray<char*>(5);
+
+  JvmtiEnvIterator it;
+  for (JvmtiEnvBase* env = it.first(); env != NULL; env = it.next(env)) {
+    int prefix_count = env->get_native_method_prefix_count();
+    char** prefixes = env->get_native_method_prefixes();
+    for (int j = 0; j < prefix_count; j++) {
+      // retrieve a prefix and so that it is safe against asynchronous changes
+      // copy it into the resource area
+      char* prefix = prefixes[j];
+      char* prefix_copy = NEW_RESOURCE_ARRAY(char, strlen(prefix)+1);
+      strcpy(prefix_copy, prefix);
+      prefix_array->at_put_grow(total_count++, prefix_copy);
+    }
+  }
+
+  char** all_prefixes = NEW_RESOURCE_ARRAY(char*, total_count);
+  char** p = all_prefixes;
+  for (int i = 0; i < total_count; ++i) {
+    *p++ = prefix_array->at(i);
+  }
+  *count_ptr = total_count;
+  return all_prefixes;
+}
+
+void
+JvmtiEnvBase::set_event_callbacks(const jvmtiEventCallbacks* callbacks,
+                                               jint size_of_callbacks) {
+  assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(), "sanity check");
+
+  size_t byte_cnt = sizeof(jvmtiEventCallbacks);
+
+  // clear in either case to be sure we got any gap between sizes
+  memset(&_event_callbacks, 0, byte_cnt);
+
+  // Now that JvmtiThreadState_lock is held, prevent a possible race condition where events
+  // are re-enabled by a call to set event callbacks where the DisposeEnvironment
+  // occurs after the boiler-plate environment check and before the lock is acquired.
+  if (callbacks != NULL && is_valid()) {
+    if (size_of_callbacks < (jint)byte_cnt) {
+      byte_cnt = size_of_callbacks;
+    }
+    memcpy(&_event_callbacks, callbacks, byte_cnt);
+  }
+}
+
+// Called from JVMTI entry points which perform stack walking. If the
+// associated JavaThread is the current thread, then wait_for_suspend
+// is not used. Otherwise, it determines if we should wait for the
+// "other" thread to complete external suspension. (NOTE: in future
+// releases the suspension mechanism should be reimplemented so this
+// is not necessary.)
+//
+bool
+JvmtiEnvBase::is_thread_fully_suspended(JavaThread* thr, bool wait_for_suspend, uint32_t *bits) {
+  // "other" threads require special handling
+  if (thr != JavaThread::current()) {
+    if (wait_for_suspend) {
+      // We are allowed to wait for the external suspend to complete
+      // so give the other thread a chance to get suspended.
+      if (!thr->wait_for_ext_suspend_completion(SuspendRetryCount,
+          SuspendRetryDelay, bits)) {
+        // didn't make it so let the caller know
+        return false;
+      }
+    }
+    // We aren't allowed to wait for the external suspend to complete
+    // so if the other thread isn't externally suspended we need to
+    // let the caller know.
+    else if (!thr->is_ext_suspend_completed_with_lock(bits)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+
+// In the fullness of time, all users of the method should instead
+// directly use allocate, besides being cleaner and faster, this will
+// mean much better out of memory handling
+unsigned char *
+JvmtiEnvBase::jvmtiMalloc(jlong size) {
+  unsigned char* mem;
+  jvmtiError result = allocate(size, &mem);
+  assert(result == JVMTI_ERROR_NONE, "Allocate failed");
+  return mem;
+}
+
+
+//
+// Threads
+//
+
+jobject *
+JvmtiEnvBase::new_jobjectArray(int length, Handle *handles) {
+  if (length == 0) {
+    return NULL;
+  }
+
+  jobject *objArray = (jobject *) jvmtiMalloc(sizeof(jobject) * length);
+  NULL_CHECK(objArray, NULL);
+
+  for (int i=0; i<length; i++) {
+    objArray[i] = jni_reference(handles[i]);
+  }
+  return objArray;
+}
+
+jthread *
+JvmtiEnvBase::new_jthreadArray(int length, Handle *handles) {
+  return (jthread *) new_jobjectArray(length,handles);
+}
+
+jthreadGroup *
+JvmtiEnvBase::new_jthreadGroupArray(int length, Handle *handles) {
+  return (jthreadGroup *) new_jobjectArray(length,handles);
+}
+
+
+JavaThread *
+JvmtiEnvBase::get_JavaThread(jthread jni_thread) {
+  oop t = JNIHandles::resolve_external_guard(jni_thread);
+  if (t == NULL || !t->is_a(SystemDictionary::thread_klass())) {
+    return NULL;
+  }
+  // The following returns NULL if the thread has not yet run or is in
+  // process of exiting
+  return java_lang_Thread::thread(t);
+}
+
+
+// update the access_flags for the field in the klass
+void
+JvmtiEnvBase::update_klass_field_access_flag(fieldDescriptor *fd) {
+  instanceKlass* ik = instanceKlass::cast(fd->field_holder());
+  typeArrayOop fields = ik->fields();
+  fields->ushort_at_put(fd->index(), (jushort)fd->access_flags().as_short());
+}
+
+
+// return the vframe on the specified thread and depth, NULL if no such frame
+vframe*
+JvmtiEnvBase::vframeFor(JavaThread* java_thread, jint depth) {
+  if (!java_thread->has_last_Java_frame()) {
+    return NULL;
+  }
+  RegisterMap reg_map(java_thread);
+  vframe *vf = java_thread->last_java_vframe(&reg_map);
+  int d = 0;
+  while ((vf != NULL) && (d < depth)) {
+    vf = vf->java_sender();
+    d++;
+  }
+  return vf;
+}
+
+
+//
+// utilities: JNI objects
+//
+
+
+jclass
+JvmtiEnvBase::get_jni_class_non_null(klassOop k) {
+  assert(k != NULL, "k != NULL");
+  return (jclass)jni_reference(Klass::cast(k)->java_mirror());
+}
+
+#ifndef JVMTI_KERNEL
+
+//
+// Field Information
+//
+
+bool
+JvmtiEnvBase::get_field_descriptor(klassOop k, jfieldID field, fieldDescriptor* fd) {
+  if (!jfieldIDWorkaround::is_valid_jfieldID(k, field)) {
+    return false;
+  }
+  bool found = false;
+  if (jfieldIDWorkaround::is_static_jfieldID(field)) {
+    JNIid* id = jfieldIDWorkaround::from_static_jfieldID(field);
+    int offset = id->offset();
+    klassOop holder = id->holder();
+    found = instanceKlass::cast(holder)->find_local_field_from_offset(offset, true, fd);
+  } else {
+    // Non-static field. The fieldID is really the offset of the field within the object.
+    int offset = jfieldIDWorkaround::from_instance_jfieldID(k, field);
+    found = instanceKlass::cast(k)->find_field_from_offset(offset, false, fd);
+  }
+  return found;
+}
+
+//
+// Object Monitor Information
+//
+
+//
+// Count the number of objects for a lightweight monitor. The hobj
+// parameter is object that owns the monitor so this routine will
+// count the number of times the same object was locked by frames
+// in java_thread.
+//
+jint
+JvmtiEnvBase::count_locked_objects(JavaThread *java_thread, Handle hobj) {
+  jint ret = 0;
+  if (!java_thread->has_last_Java_frame()) {
+    return ret;  // no Java frames so no monitors
+  }
+
+  ResourceMark rm;
+  HandleMark   hm;
+  RegisterMap  reg_map(java_thread);
+
+  for(javaVFrame *jvf=java_thread->last_java_vframe(&reg_map); jvf != NULL;
+                                                 jvf = jvf->java_sender()) {
+    GrowableArray<MonitorInfo*>* mons = jvf->monitors();
+    if (!mons->is_empty()) {
+      for (int i = 0; i < mons->length(); i++) {
+        MonitorInfo *mi = mons->at(i);
+
+        // see if owner of the monitor is our object
+        if (mi->owner() != NULL && mi->owner() == hobj()) {
+          ret++;
+        }
+      }
+    }
+  }
+  return ret;
+}
+
+
+
+jvmtiError
+JvmtiEnvBase::get_current_contended_monitor(JavaThread *calling_thread, JavaThread *java_thread, jobject *monitor_ptr) {
+#ifdef ASSERT
+  uint32_t debug_bits = 0;
+#endif
+  assert((SafepointSynchronize::is_at_safepoint() ||
+          is_thread_fully_suspended(java_thread, false, &debug_bits)),
+         "at safepoint or target thread is suspended");
+  oop obj = NULL;
+  ObjectMonitor *mon = java_thread->current_waiting_monitor();
+  if (mon == NULL) {
+    // thread is not doing an Object.wait() call
+    mon = java_thread->current_pending_monitor();
+    if (mon != NULL) {
+      // The thread is trying to enter() or raw_enter() an ObjectMonitor.
+      obj = (oop)mon->object();
+      // If obj == NULL, then ObjectMonitor is raw which doesn't count
+      // as contended for this API
+    }
+    // implied else: no contended ObjectMonitor
+  } else {
+    // thread is doing an Object.wait() call
+    obj = (oop)mon->object();
+    assert(obj != NULL, "Object.wait() should have an object");
+  }
+
+  if (obj == NULL) {
+    *monitor_ptr = NULL;
+  } else {
+    HandleMark hm;
+    Handle     hobj(obj);
+    *monitor_ptr = jni_reference(calling_thread, hobj);
+  }
+  return JVMTI_ERROR_NONE;
+}
+
+
+jvmtiError
+JvmtiEnvBase::get_owned_monitors(JavaThread *calling_thread, JavaThread* java_thread,
+                                 GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors_list) {
+  jvmtiError err = JVMTI_ERROR_NONE;
+#ifdef ASSERT
+  uint32_t debug_bits = 0;
+#endif
+  assert((SafepointSynchronize::is_at_safepoint() ||
+          is_thread_fully_suspended(java_thread, false, &debug_bits)),
+         "at safepoint or target thread is suspended");
+
+  if (java_thread->has_last_Java_frame()) {
+    ResourceMark rm;
+    HandleMark   hm;
+    RegisterMap  reg_map(java_thread);
+
+    int depth = 0;
+    for (javaVFrame *jvf = java_thread->last_java_vframe(&reg_map); jvf != NULL;
+         jvf = jvf->java_sender()) {
+      if (depth++ < MaxJavaStackTraceDepth) {  // check for stack too deep
+        // add locked objects for this frame into list
+        err = get_locked_objects_in_frame(calling_thread, java_thread, jvf, owned_monitors_list, depth-1);
+        if (err != JVMTI_ERROR_NONE) {
+          return err;
+        }
+      }
+    }
+  }
+
+  // Get off stack monitors. (e.g. acquired via jni MonitorEnter).
+  JvmtiMonitorClosure jmc(java_thread, calling_thread, owned_monitors_list, this);
+  ObjectSynchronizer::monitors_iterate(&jmc);
+  err = jmc.error();
+
+  return err;
+}
+
+// Save JNI local handles for any objects that this frame owns.
+jvmtiError
+JvmtiEnvBase::get_locked_objects_in_frame(JavaThread* calling_thread, JavaThread* java_thread,
+                                 javaVFrame *jvf, GrowableArray<jvmtiMonitorStackDepthInfo*>* owned_monitors_list, int stack_depth) {
+  jvmtiError err = JVMTI_ERROR_NONE;
+  ResourceMark rm;
+
+  GrowableArray<MonitorInfo*>* mons = jvf->monitors();
+  if (mons->is_empty()) {
+    return err;  // this javaVFrame holds no monitors
+  }
+
+  HandleMark hm;
+  oop wait_obj = NULL;
+  {
+    // save object of current wait() call (if any) for later comparison
+    ObjectMonitor *mon = java_thread->current_waiting_monitor();
+    if (mon != NULL) {
+      wait_obj = (oop)mon->object();
+    }
+  }
+  oop pending_obj = NULL;
+  {
+    // save object of current enter() call (if any) for later comparison
+    ObjectMonitor *mon = java_thread->current_pending_monitor();
+    if (mon != NULL) {
+      pending_obj = (oop)mon->object();
+    }
+  }
+
+  for (int i = 0; i < mons->length(); i++) {
+    MonitorInfo *mi = mons->at(i);
+
+    oop obj = mi->owner();
+    if (obj == NULL) {
+      // this monitor doesn't have an owning object so skip it
+      continue;
+    }
+
+    if (wait_obj == obj) {
+      // the thread is waiting on this monitor so it isn't really owned
+      continue;
+    }
+
+    if (pending_obj == obj) {
+      // the thread is pending on this monitor so it isn't really owned
+      continue;
+    }
+
+    if (owned_monitors_list->length() > 0) {
+      // Our list has at least one object on it so we have to check
+      // for recursive object locking
+      bool found = false;
+      for (int j = 0; j < owned_monitors_list->length(); j++) {
+        jobject jobj = ((jvmtiMonitorStackDepthInfo*)owned_monitors_list->at(j))->monitor;
+        oop check = JNIHandles::resolve(jobj);
+        if (check == obj) {
+          found = true;  // we found the object
+          break;
+        }
+      }
+
+      if (found) {
+        // already have this object so don't include it
+        continue;
+      }
+    }
+
+    // add the owning object to our list
+    jvmtiMonitorStackDepthInfo *jmsdi;
+    err = allocate(sizeof(jvmtiMonitorStackDepthInfo), (unsigned char **)&jmsdi);
+    if (err != JVMTI_ERROR_NONE) {
+        return err;
+    }
+    Handle hobj(obj);
+    jmsdi->monitor = jni_reference(calling_thread, hobj);
+    jmsdi->stack_depth = stack_depth;
+    owned_monitors_list->append(jmsdi);
+  }
+
+  return err;
+}
+
+jvmtiError
+JvmtiEnvBase::get_stack_trace(JavaThread *java_thread,
+                              jint start_depth, jint max_count,
+                              jvmtiFrameInfo* frame_buffer, jint* count_ptr) {
+#ifdef ASSERT
+  uint32_t debug_bits = 0;
+#endif
+  assert((SafepointSynchronize::is_at_safepoint() ||
+          is_thread_fully_suspended(java_thread, false, &debug_bits)),
+         "at safepoint or target thread is suspended");
+  int count = 0;
+  if (java_thread->has_last_Java_frame()) {
+    RegisterMap reg_map(java_thread);
+    Thread* current_thread = Thread::current();
+    ResourceMark rm(current_thread);
+    javaVFrame *jvf = java_thread->last_java_vframe(&reg_map);
+    HandleMark hm(current_thread);
+    if (start_depth != 0) {
+      if (start_depth > 0) {
+        for (int j = 0; j < start_depth && jvf != NULL; j++) {
+          jvf = jvf->java_sender();
+        }
+        if (jvf == NULL) {
+          // start_depth is deeper than the stack depth
+          return JVMTI_ERROR_ILLEGAL_ARGUMENT;
+        }
+      } else { // start_depth < 0
+        // we are referencing the starting depth based on the oldest
+        // part of the stack.
+        // optimize to limit the number of times that java_sender() is called
+        javaVFrame *jvf_cursor = jvf;
+        javaVFrame *jvf_prev = NULL;
+        javaVFrame *jvf_prev_prev;
+        int j = 0;
+        while (jvf_cursor != NULL) {
+          jvf_prev_prev = jvf_prev;
+          jvf_prev = jvf_cursor;
+          for (j = 0; j > start_depth && jvf_cursor != NULL; j--) {
+            jvf_cursor = jvf_cursor->java_sender();
+          }
+        }
+        if (j == start_depth) {
+          // previous pointer is exactly where we want to start
+          jvf = jvf_prev;
+        } else {
+          // we need to back up further to get to the right place
+          if (jvf_prev_prev == NULL) {
+            // the -start_depth is greater than the stack depth
+            return JVMTI_ERROR_ILLEGAL_ARGUMENT;
+          }
+          // j now is the number of frames on the stack starting with
+          // jvf_prev, we start from jvf_prev_prev and move older on
+          // the stack that many, the result is -start_depth frames
+          // remaining.
+          jvf = jvf_prev_prev;
+          for (; j < 0; j++) {
+            jvf = jvf->java_sender();
+          }
+        }
+      }
+    }
+    for (; count < max_count && jvf != NULL; count++) {
+      frame_buffer[count].method = jvf->method()->jmethod_id();
+      frame_buffer[count].location = (jvf->method()->is_native() ? -1 : jvf->bci());
+      jvf = jvf->java_sender();
+    }
+  } else {
+    if (start_depth != 0) {
+      // no frames and there is a starting depth
+      return JVMTI_ERROR_ILLEGAL_ARGUMENT;
+    }
+  }
+  *count_ptr = count;
+  return JVMTI_ERROR_NONE;
+}
+
+jvmtiError
+JvmtiEnvBase::get_frame_count(JvmtiThreadState *state, jint *count_ptr) {
+  assert((state != NULL),
+         "JavaThread should create JvmtiThreadState before calling this method");
+  *count_ptr = state->count_frames();
+  return JVMTI_ERROR_NONE;
+}
+
+jvmtiError
+JvmtiEnvBase::get_frame_location(JavaThread *java_thread, jint depth,
+                                 jmethodID* method_ptr, jlocation* location_ptr) {
+#ifdef ASSERT
+  uint32_t debug_bits = 0;
+#endif
+  assert((SafepointSynchronize::is_at_safepoint() ||
+          is_thread_fully_suspended(java_thread, false, &debug_bits)),
+         "at safepoint or target thread is suspended");
+  Thread* current_thread = Thread::current();
+  ResourceMark rm(current_thread);
+
+  vframe *vf = vframeFor(java_thread, depth);
+  if (vf == NULL) {
+    return JVMTI_ERROR_NO_MORE_FRAMES;
+  }
+
+  // vframeFor should return a java frame. If it doesn't
+  // it means we've got an internal error and we return the
+  // error in product mode. In debug mode we will instead
+  // attempt to cast the vframe to a javaVFrame and will
+  // cause an assertion/crash to allow further diagnosis.
+#ifdef PRODUCT
+  if (!vf->is_java_frame()) {
+    return JVMTI_ERROR_INTERNAL;
+  }
+#endif
+
+  HandleMark hm(current_thread);
+  javaVFrame *jvf = javaVFrame::cast(vf);
+  methodOop method = jvf->method();
+  if (method->is_native()) {
+    *location_ptr = -1;
+  } else {
+    *location_ptr = jvf->bci();
+  }
+  *method_ptr = method->jmethod_id();
+
+  return JVMTI_ERROR_NONE;
+}
+
+
+jvmtiError
+JvmtiEnvBase::get_object_monitor_usage(JavaThread* calling_thread, jobject object, jvmtiMonitorUsage* info_ptr) {
+  HandleMark hm;
+  Handle hobj;
+
+  bool at_safepoint = SafepointSynchronize::is_at_safepoint();
+
+  // Check arguments
+  {
+    oop mirror = JNIHandles::resolve_external_guard(object);
+    NULL_CHECK(mirror, JVMTI_ERROR_INVALID_OBJECT);
+    NULL_CHECK(info_ptr, JVMTI_ERROR_NULL_POINTER);
+
+    hobj = Handle(mirror);
+  }
+
+  JavaThread *owning_thread = NULL;
+  ObjectMonitor *mon = NULL;
+  jvmtiMonitorUsage ret = {
+      NULL, 0, 0, NULL, 0, NULL
+  };
+
+  uint32_t debug_bits = 0;
+  // first derive the object's owner and entry_count (if any)
+  {
+    // Revoke any biases before querying the mark word
+    if (SafepointSynchronize::is_at_safepoint()) {
+      BiasedLocking::revoke_at_safepoint(hobj);
+    } else {
+      BiasedLocking::revoke_and_rebias(hobj, false, calling_thread);
+    }
+
+    address owner = NULL;
+    {
+      markOop mark = hobj()->mark();
+
+      if (!mark->has_monitor()) {
+        // this object has a lightweight monitor
+
+        if (mark->has_locker()) {
+          owner = (address)mark->locker(); // save the address of the Lock word
+        }
+        // implied else: no owner
+      } else {
+        // this object has a heavyweight monitor
+        mon = mark->monitor();
+
+        // The owner field of a heavyweight monitor may be NULL for no
+        // owner, a JavaThread * or it may still be the address of the
+        // Lock word in a JavaThread's stack. A monitor can be inflated
+        // by a non-owning JavaThread, but only the owning JavaThread
+        // can change the owner field from the Lock word to the
+        // JavaThread * and it may not have done that yet.
+        owner = (address)mon->owner();
+      }
+    }
+
+    if (owner != NULL) {
+      // This monitor is owned so we have to find the owning JavaThread.
+      // Since owning_thread_from_monitor_owner() grabs a lock, GC can
+      // move our object at this point. However, our owner value is safe
+      // since it is either the Lock word on a stack or a JavaThread *.
+      owning_thread = Threads::owning_thread_from_monitor_owner(owner, !at_safepoint);
+      assert(owning_thread != NULL, "sanity check");
+      if (owning_thread != NULL) {  // robustness
+        // The monitor's owner either has to be the current thread, at safepoint
+        // or it has to be suspended. Any of these conditions will prevent both
+        // contending and waiting threads from modifying the state of
+        // the monitor.
+        if (!at_safepoint && !JvmtiEnv::is_thread_fully_suspended(owning_thread, true, &debug_bits)) {
+          return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
+        }
+        HandleMark hm;
+        Handle     th(owning_thread->threadObj());
+        ret.owner = (jthread)jni_reference(calling_thread, th);
+      }
+      // implied else: no owner
+    }
+
+    if (owning_thread != NULL) {  // monitor is owned
+      if ((address)owning_thread == owner) {
+        // the owner field is the JavaThread *
+        assert(mon != NULL,
+          "must have heavyweight monitor with JavaThread * owner");
+        ret.entry_count = mon->recursions() + 1;
+      } else {
+        // The owner field is the Lock word on the JavaThread's stack
+        // so the recursions field is not valid. We have to count the
+        // number of recursive monitor entries the hard way. We pass
+        // a handle to survive any GCs along the way.
+        ResourceMark rm;
+        ret.entry_count = count_locked_objects(owning_thread, hobj);
+      }
+    }
+    // implied else: entry_count == 0
+  }
+
+  int nWant,nWait;
+  if (mon != NULL) {
+    // this object has a heavyweight monitor
+    nWant = mon->contentions(); // # of threads contending for monitor
+    nWait = mon->waiters();     // # of threads in Object.wait()
+    ret.waiter_count = nWant + nWait;
+    ret.notify_waiter_count = nWait;
+  } else {
+    // this object has a lightweight monitor
+    ret.waiter_count = 0;
+    ret.notify_waiter_count = 0;
+  }
+
+  // Allocate memory for heavyweight and lightweight monitor.
+  jvmtiError err;
+  err = allocate(ret.waiter_count * sizeof(jthread *), (unsigned char**)&ret.waiters);
+  if (err != JVMTI_ERROR_NONE) {
+    return err;
+  }
+  err = allocate(ret.notify_waiter_count * sizeof(jthread *),
+                 (unsigned char**)&ret.notify_waiters);
+  if (err != JVMTI_ERROR_NONE) {
+    deallocate((unsigned char*)ret.waiters);
+    return err;
+  }
+
+  // now derive the rest of the fields
+  if (mon != NULL) {
+    // this object has a heavyweight monitor
+
+    // Number of waiters may actually be less than the waiter count.
+    // So NULL out memory so that unused memory will be NULL.
+    memset(ret.waiters, 0, ret.waiter_count * sizeof(jthread *));
+    memset(ret.notify_waiters, 0, ret.notify_waiter_count * sizeof(jthread *));
+
+    if (ret.waiter_count > 0) {
+      // we have contending and/or waiting threads
+      HandleMark hm;
+      if (nWant > 0) {
+        // we have contending threads
+        ResourceMark rm;
+        // get_pending_threads returns only java thread so we do not need to
+        // check for  non java threads.
+        GrowableArray<JavaThread*>* wantList = Threads::get_pending_threads(
+          nWant, (address)mon, !at_safepoint);
+        if (wantList->length() < nWant) {
+          // robustness: the pending list has gotten smaller
+          nWant = wantList->length();
+        }
+        for (int i = 0; i < nWant; i++) {
+          JavaThread *pending_thread = wantList->at(i);
+          // If the monitor has no owner, then a non-suspended contending
+          // thread could potentially change the state of the monitor by
+          // entering it. The JVM/TI spec doesn't allow this.
+          if (owning_thread == NULL && !at_safepoint &
+              !JvmtiEnv::is_thread_fully_suspended(pending_thread, true, &debug_bits)) {
+            if (ret.owner != NULL) {
+              destroy_jni_reference(calling_thread, ret.owner);
+            }
+            for (int j = 0; j < i; j++) {
+              destroy_jni_reference(calling_thread, ret.waiters[j]);
+            }
+            deallocate((unsigned char*)ret.waiters);
+            deallocate((unsigned char*)ret.notify_waiters);
+            return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
+          }
+          Handle th(pending_thread->threadObj());
+          ret.waiters[i] = (jthread)jni_reference(calling_thread, th);
+        }
+      }
+      if (nWait > 0) {
+        // we have threads in Object.wait()
+        int offset = nWant;  // add after any contending threads
+        ObjectWaiter *waiter = mon->first_waiter();
+        for (int i = 0, j = 0; i < nWait; i++) {
+          if (waiter == NULL) {
+            // robustness: the waiting list has gotten smaller
+            nWait = j;
+            break;
+          }
+          Thread *t = mon->thread_of_waiter(waiter);
+          if (t != NULL && t->is_Java_thread()) {
+            JavaThread *wjava_thread = (JavaThread *)t;
+            // If the thread was found on the ObjectWaiter list, then
+            // it has not been notified. This thread can't change the
+            // state of the monitor so it doesn't need to be suspended.
+            Handle th(wjava_thread->threadObj());
+            ret.waiters[offset + j] = (jthread)jni_reference(calling_thread, th);
+            ret.notify_waiters[j++] = (jthread)jni_reference(calling_thread, th);
+          }
+          waiter = mon->next_waiter(waiter);
+        }
+      }
+    }
+
+    // Adjust count. nWant and nWait count values may be less than original.
+    ret.waiter_count = nWant + nWait;
+    ret.notify_waiter_count = nWait;
+  } else {
+    // this object has a lightweight monitor and we have nothing more
+    // to do here because the defaults are just fine.
+  }
+
+  // we don't update return parameter unless everything worked
+  *info_ptr = ret;
+
+  return JVMTI_ERROR_NONE;
+}
+
+ResourceTracker::ResourceTracker(JvmtiEnv* env) {
+  _env = env;
+  _allocations = new (ResourceObj::C_HEAP) GrowableArray<unsigned char*>(20, true);
+  _failed = false;
+}
+ResourceTracker::~ResourceTracker() {
+  if (_failed) {
+    for (int i=0; i<_allocations->length(); i++) {
+      _env->deallocate(_allocations->at(i));
+    }
+  }
+  delete _allocations;
+}
+
+jvmtiError ResourceTracker::allocate(jlong size, unsigned char** mem_ptr) {
+  unsigned char *ptr;
+  jvmtiError err = _env->allocate(size, &ptr);
+  if (err == JVMTI_ERROR_NONE) {
+    _allocations->append(ptr);
+    *mem_ptr = ptr;
+  } else {
+    *mem_ptr = NULL;
+    _failed = true;
+  }
+  return err;
+ }
+
+unsigned char* ResourceTracker::allocate(jlong size) {
+  unsigned char* ptr;
+  allocate(size, &ptr);
+  return ptr;
+}
+
+char* ResourceTracker::strdup(const char* str) {
+  char *dup_str = (char*)allocate(strlen(str)+1);
+  if (dup_str != NULL) {
+    strcpy(dup_str, str);
+  }
+  return dup_str;
+}
+
+struct StackInfoNode {
+  struct StackInfoNode *next;
+  jvmtiStackInfo info;
+};
+
+// Create a jvmtiStackInfo inside a linked list node and create a
+// buffer for the frame information, both allocated as resource objects.
+// Fill in both the jvmtiStackInfo and the jvmtiFrameInfo.
+// Note that either or both of thr and thread_oop
+// may be null if the thread is new or has exited.
+void
+VM_GetMultipleStackTraces::fill_frames(jthread jt, JavaThread *thr, oop thread_oop) {
+  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
+
+  jint state = 0;
+  struct StackInfoNode *node = NEW_RESOURCE_OBJ(struct StackInfoNode);
+  jvmtiStackInfo *infop = &(node->info);
+  node->next = head();
+  set_head(node);
+  infop->frame_count = 0;
+  infop->thread = jt;
+
+  if (thread_oop != NULL) {
+    // get most state bits
+    state = (jint)java_lang_Thread::get_thread_status(thread_oop);
+  }
+
+  if (thr != NULL) {    // add more state bits if there is a JavaThead to query
+    // same as is_being_ext_suspended() but without locking
+    if (thr->is_ext_suspended() || thr->is_external_suspend()) {
+      state |= JVMTI_THREAD_STATE_SUSPENDED;
+    }
+    JavaThreadState jts = thr->thread_state();
+    if (jts == _thread_in_native) {
+      state |= JVMTI_THREAD_STATE_IN_NATIVE;
+    }
+    OSThread* osThread = thr->osthread();
+    if (osThread != NULL && osThread->interrupted()) {
+      state |= JVMTI_THREAD_STATE_INTERRUPTED;
+    }
+  }
+  infop->state = state;
+
+  if (thr != NULL || (state & JVMTI_THREAD_STATE_ALIVE) != 0) {
+    infop->frame_buffer = NEW_RESOURCE_ARRAY(jvmtiFrameInfo, max_frame_count());
+    env()->get_stack_trace(thr, 0, max_frame_count(),
+                           infop->frame_buffer, &(infop->frame_count));
+  } else {
+    infop->frame_buffer = NULL;
+    infop->frame_count = 0;
+  }
+  _frame_count_total += infop->frame_count;
+}
+
+// Based on the stack information in the linked list, allocate memory
+// block to return and fill it from the info in the linked list.
+void
+VM_GetMultipleStackTraces::allocate_and_fill_stacks(jint thread_count) {
+  // do I need to worry about alignment issues?
+  jlong alloc_size =  thread_count       * sizeof(jvmtiStackInfo)
+                    + _frame_count_total * sizeof(jvmtiFrameInfo);
+  env()->allocate(alloc_size, (unsigned char **)&_stack_info);
+
+  // pointers to move through the newly allocated space as it is filled in
+  jvmtiStackInfo *si = _stack_info + thread_count;      // bottom of stack info
+  jvmtiFrameInfo *fi = (jvmtiFrameInfo *)si;            // is the top of frame info
+
+  // copy information in resource area into allocated buffer
+  // insert stack info backwards since linked list is backwards
+  // insert frame info forwards
+  // walk the StackInfoNodes
+  for (struct StackInfoNode *sin = head(); sin != NULL; sin = sin->next) {
+    jint frame_count = sin->info.frame_count;
+    size_t frames_size = frame_count * sizeof(jvmtiFrameInfo);
+    --si;
+    memcpy(si, &(sin->info), sizeof(jvmtiStackInfo));
+    if (frames_size == 0) {
+      si->frame_buffer = NULL;
+    } else {
+      memcpy(fi, sin->info.frame_buffer, frames_size);
+      si->frame_buffer = fi;  // point to the new allocated copy of the frames
+      fi += frame_count;
+    }
+  }
+  assert(si == _stack_info, "the last copied stack info must be the first record");
+  assert((unsigned char *)fi == ((unsigned char *)_stack_info) + alloc_size,
+         "the last copied frame info must be the last record");
+}
+
+
+void
+VM_GetThreadListStackTraces::doit() {
+  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
+
+  ResourceMark rm;
+  for (int i = 0; i < _thread_count; ++i) {
+    jthread jt = _thread_list[i];
+    oop thread_oop = JNIHandles::resolve_external_guard(jt);
+    if (thread_oop == NULL || !thread_oop->is_a(SystemDictionary::thread_klass())) {
+      set_result(JVMTI_ERROR_INVALID_THREAD);
+      return;
+    }
+    fill_frames(jt, java_lang_Thread::thread(thread_oop), thread_oop);
+  }
+  allocate_and_fill_stacks(_thread_count);
+}
+
+void
+VM_GetAllStackTraces::doit() {
+  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
+
+  ResourceMark rm;
+  _final_thread_count = 0;
+  for (JavaThread *jt = Threads::first(); jt != NULL; jt = jt->next()) {
+    oop thread_oop = jt->threadObj();
+    if (thread_oop != NULL &&
+        !jt->is_exiting() &&
+        java_lang_Thread::is_alive(thread_oop) &&
+        !jt->is_hidden_from_external_view()) {
+      ++_final_thread_count;
+      // Handle block of the calling thread is used to create local refs.
+      fill_frames((jthread)JNIHandles::make_local(_calling_thread, thread_oop),
+                  jt, thread_oop);
+    }
+  }
+  allocate_and_fill_stacks(_final_thread_count);
+}
+
+// Verifies that the top frame is a java frame in an expected state.
+// Deoptimizes frame if needed.
+// Checks that the frame method signature matches the return type (tos).
+// HandleMark must be defined in the caller only.
+// It is to keep a ret_ob_h handle alive after return to the caller.
+jvmtiError
+JvmtiEnvBase::check_top_frame(JavaThread* current_thread, JavaThread* java_thread,
+                              jvalue value, TosState tos, Handle* ret_ob_h) {
+  ResourceMark rm(current_thread);
+
+  vframe *vf = vframeFor(java_thread, 0);
+  NULL_CHECK(vf, JVMTI_ERROR_NO_MORE_FRAMES);
+
+  javaVFrame *jvf = (javaVFrame*) vf;
+  if (!vf->is_java_frame() || jvf->method()->is_native()) {
+    return JVMTI_ERROR_OPAQUE_FRAME;
+  }
+
+  // If the frame is a compiled one, need to deoptimize it.
+  if (vf->is_compiled_frame()) {
+    if (!vf->fr().can_be_deoptimized()) {
+      return JVMTI_ERROR_OPAQUE_FRAME;
+    }
+    VM_DeoptimizeFrame deopt(java_thread, jvf->fr().id());
+    VMThread::execute(&deopt);
+  }
+
+  // Get information about method return type
+  symbolHandle signature(current_thread, jvf->method()->signature());
+
+  ResultTypeFinder rtf(signature);
+  TosState fr_tos = as_TosState(rtf.type());
+  if (fr_tos != tos) {
+    if (tos != itos || (fr_tos != btos && fr_tos != ctos && fr_tos != stos)) {
+      return JVMTI_ERROR_TYPE_MISMATCH;
+    }
+  }
+
+  // Check that the jobject class matches the return type signature.
+  jobject jobj = value.l;
+  if (tos == atos && jobj != NULL) { // NULL reference is allowed
+    Handle ob_h = Handle(current_thread, JNIHandles::resolve_external_guard(jobj));
+    NULL_CHECK(ob_h, JVMTI_ERROR_INVALID_OBJECT);
+    KlassHandle ob_kh = KlassHandle(current_thread, ob_h()->klass());
+    NULL_CHECK(ob_kh, JVMTI_ERROR_INVALID_OBJECT);
+
+    // Method return type signature.
+    char* ty_sign = 1 + strchr(signature->as_C_string(), ')');
+
+    if (!VM_GetOrSetLocal::is_assignable(ty_sign, Klass::cast(ob_kh()), current_thread)) {
+      return JVMTI_ERROR_TYPE_MISMATCH;
+    }
+    *ret_ob_h = ob_h;
+  }
+  return JVMTI_ERROR_NONE;
+} /* end check_top_frame */
+
+
+// ForceEarlyReturn<type> follows the PopFrame approach in many aspects.
+// Main difference is on the last stage in the interpreter.
+// The PopFrame stops method execution to continue execution
+// from the same method call instruction.
+// The ForceEarlyReturn forces return from method so the execution
+// continues at the bytecode following the method call.
+
+// Threads_lock NOT held, java_thread not protected by lock
+// java_thread - pre-checked
+
+jvmtiError
+JvmtiEnvBase::force_early_return(JavaThread* java_thread, jvalue value, TosState tos) {
+  JavaThread* current_thread = JavaThread::current();
+  HandleMark   hm(current_thread);
+  uint32_t debug_bits = 0;
+
+  // Check if java_thread is fully suspended
+  if (!is_thread_fully_suspended(java_thread,
+                                 true /* wait for suspend completion */,
+                                 &debug_bits)) {
+    return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
+  }
+
+  // retreive or create the state
+  JvmtiThreadState* state = JvmtiThreadState::state_for(java_thread);
+
+  // Check to see if a ForceEarlyReturn was already in progress
+  if (state->is_earlyret_pending()) {
+    // Probably possible for JVMTI clients to trigger this, but the
+    // JPDA backend shouldn't allow this to happen
+    return JVMTI_ERROR_INTERNAL;
+  }
+  {
+    // The same as for PopFrame. Workaround bug:
+    //  4812902: popFrame hangs if the method is waiting at a synchronize
+    // Catch this condition and return an error to avoid hanging.
+    // Now JVMTI spec allows an implementation to bail out with an opaque
+    // frame error.
+    OSThread* osThread = java_thread->osthread();
+    if (osThread->get_state() == MONITOR_WAIT) {
+      return JVMTI_ERROR_OPAQUE_FRAME;
+    }
+  }
+  Handle ret_ob_h = Handle();
+  jvmtiError err = check_top_frame(current_thread, java_thread, value, tos, &ret_ob_h);
+  if (err != JVMTI_ERROR_NONE) {
+    return err;
+  }
+  assert(tos != atos || value.l == NULL || ret_ob_h() != NULL,
+         "return object oop must not be NULL if jobject is not NULL");
+
+  // Update the thread state to reflect that the top frame must be
+  // forced to return.
+  // The current frame will be returned later when the suspended
+  // thread is resumed and right before returning from VM to Java.
+  // (see call_VM_base() in assembler_<cpu>.cpp).
+
+  state->set_earlyret_pending();
+  state->set_earlyret_oop(ret_ob_h());
+  state->set_earlyret_value(value, tos);
+
+  // Set pending step flag for this early return.
+  // It is cleared when next step event is posted.
+  state->set_pending_step_for_earlyret();
+
+  return JVMTI_ERROR_NONE;
+} /* end force_early_return */
+
+void
+JvmtiMonitorClosure::do_monitor(ObjectMonitor* mon) {
+  if ( _error != JVMTI_ERROR_NONE) {
+    // Error occurred in previous iteration so no need to add
+    // to the list.
+    return;
+  }
+  if (mon->owner() == _java_thread ) {
+    // Filter out on stack monitors collected during stack walk.
+    oop obj = (oop)mon->object();
+    bool found = false;
+    for (int j = 0; j < _owned_monitors_list->length(); j++) {
+      jobject jobj = ((jvmtiMonitorStackDepthInfo*)_owned_monitors_list->at(j))->monitor;
+      oop check = JNIHandles::resolve(jobj);
+      if (check == obj) {
+        // On stack monitor already collected during the stack walk.
+        found = true;
+        break;
+      }
+    }
+    if (found == false) {
+      // This is off stack monitor (e.g. acquired via jni MonitorEnter).
+      jvmtiError err;
+      jvmtiMonitorStackDepthInfo *jmsdi;
+      err = _env->allocate(sizeof(jvmtiMonitorStackDepthInfo), (unsigned char **)&jmsdi);
+      if (err != JVMTI_ERROR_NONE) {
+        _error = err;
+        return;
+      }
+      Handle hobj(obj);
+      jmsdi->monitor = _env->jni_reference(_calling_thread, hobj);
+      // stack depth is unknown for this monitor.
+      jmsdi->stack_depth = -1;
+      _owned_monitors_list->append(jmsdi);
+    }
+  }
+}
+
+#endif // !JVMTI_KERNEL