view src/share/vm/runtime/java.hpp @ 2682:eca1193ca245

4965777: GC changes to support use of discovered field for pending references Summary: If and when the reference handler thread is able to use the discovered field to link reference objects in its pending list, so will GC. In that case, GC will scan through this field once a reference object has been placed on the pending list, but not scan that field before that stage, as the field is used by the concurrent GC thread to link discovered objects. When ReferenceHandleR thread does not use the discovered field for the purpose of linking the elements in the pending list, as would be the case in older JDKs, the JVM will fall back to the old behaviour of using the next field for that purpose. Reviewed-by: jcoomes, mchung, stefank
author ysr
date Wed, 07 Sep 2011 13:55:42 -0700
parents 3582bf76420e
children 9d679effd28c
line wrap: on
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 * Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.
 * 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 if you need additional information or have any
 * questions.


#include "runtime/os.hpp"

// Register function to be called by before_exit
extern "C" { void register_on_exit_function(void (*func)(void)) ;}

// Execute code before all handles are released and thread is killed; prologue to vm_exit
extern void before_exit(JavaThread * thread);

// Forced VM exit (i.e, internal error or JVM_Exit)
extern void vm_exit(int code);

// Wrapper for ::exit()
extern void vm_direct_exit(int code);

// Shutdown the VM but do not exit the process
extern void vm_shutdown();
// Shutdown the VM and abort the process
extern void vm_abort(bool dump_core=true);

// Trigger any necessary notification of the VM being shutdown
extern void notify_vm_shutdown();

// VM exit if error occurs during initialization of VM
extern void vm_exit_during_initialization(Handle exception);
extern void vm_exit_during_initialization(Symbol* exception_name, const char* message);
extern void vm_exit_during_initialization(const char* error, const char* message = NULL);
extern void vm_shutdown_during_initialization(const char* error, const char* message = NULL);

 * Discovering the JDK_Version during initialization is tricky when the
 * running JDK is less than JDK6.  For JDK6 and greater, a "GetVersion"
 * function exists in and we simply call it during the
 * 'initialize()' call to find the version.  For JDKs with version < 6, no
 * such call exists and we have to probe the JDK in order to determine
 * the exact version.  This probing cannot happen during late in
 * the VM initialization process so there's a period of time during
 * initialization when we don't know anything about the JDK version other than
 * that it less than version 6.  This is the "partially initialized" time,
 * when we can answer only certain version queries (such as, is the JDK
 * version greater than 5?  Answer: no).  Once the JDK probing occurs, we
 * know the version and are considered fully initialized.
  friend class VMStructs;
  friend class Universe;
  friend void JDK_Version_init();

  static JDK_Version _current;

  // In this class, we promote the minor version of release to be the
  // major version for releases >= 5 in anticipation of the JDK doing the
  // same thing.  For example, we represent "1.5.0" as major version 5 (we
  // drop the leading 1 and use 5 as the 'major').

  uint8_t _major;
  uint8_t _minor;
  uint8_t _micro;
  uint8_t _update;
  uint8_t _special;
  uint8_t _build;

  // If partially initialized, the above fields are invalid and we know
  // that we're less than major version 6.
  bool _partially_initialized;

  bool _thread_park_blocker;
  bool _pending_list_uses_discovered_field;
  bool _post_vm_init_hook_enabled;

  bool is_valid() const {
    return (_major != 0 || _partially_initialized);

  // initializes or partially initializes the _current static field
  static void initialize();

  // Completes initialization for a pre-JDK6 version.
  static void fully_initialize(uint8_t major, uint8_t minor = 0,
                               uint8_t micro = 0, uint8_t update = 0);


  // Returns true if the the current version has only been partially initialized
  static bool is_partially_initialized() {
    return _current._partially_initialized;

  JDK_Version() : _major(0), _minor(0), _micro(0), _update(0),
                  _special(0), _build(0), _partially_initialized(false),
                  _thread_park_blocker(false), _post_vm_init_hook_enabled(false),
                  _pending_list_uses_discovered_field(false) {}

  JDK_Version(uint8_t major, uint8_t minor = 0, uint8_t micro = 0,
              uint8_t update = 0, uint8_t special = 0, uint8_t build = 0,
              bool thread_park_blocker = false, bool post_vm_init_hook_enabled = false,
              bool pending_list_uses_discovered_field = false) :
      _major(major), _minor(minor), _micro(micro), _update(update),
      _special(special), _build(build), _partially_initialized(false),
      _pending_list_uses_discovered_field(pending_list_uses_discovered_field) {}

  // Returns the current running JDK version
  static JDK_Version current() { return _current; }

  // Factory methods for convenience
  static JDK_Version jdk(uint8_t m) {
    return JDK_Version(m);

  static JDK_Version jdk_update(uint8_t major, uint8_t update_number) {
    return JDK_Version(major, 0, 0, update_number);

  uint8_t major_version() const          { return _major; }
  uint8_t minor_version() const          { return _minor; }
  uint8_t micro_version() const          { return _micro; }
  uint8_t update_version() const         { return _update; }
  uint8_t special_update_version() const { return _special; }
  uint8_t build_number() const           { return _build; }

  bool supports_thread_park_blocker() const {
    return _thread_park_blocker;
  bool post_vm_init_hook_enabled() const {
    return _post_vm_init_hook_enabled;
  // For compatibility wrt pre-4965777 JDK's
  bool pending_list_uses_discovered_field() const {
    return _pending_list_uses_discovered_field;

  // Performs a full ordering comparison using all fields (update, build, etc.)
  int compare(const JDK_Version& other) const;

   * Performs comparison using only the major version, returning negative
   * if the major version of 'this' is less than the parameter, 0 if it is
   * equal, and a positive value if it is greater.
  int compare_major(int version) const {
    if (_partially_initialized) {
      if (version >= 6) {
        return -1;
      } else {
        assert(false, "Can't make this comparison during init time");
        return -1; // conservative
    } else {
      return major_version() - version;

  void to_string(char* buffer, size_t buflen) const;

  // Convenience methods for queries on the current major/minor version
  static bool is_jdk12x_version() {
    return current().compare_major(2) == 0;

  static bool is_jdk13x_version() {
    return current().compare_major(3) == 0;

  static bool is_jdk14x_version() {
    return current().compare_major(4) == 0;

  static bool is_jdk15x_version() {
    return current().compare_major(5) == 0;

  static bool is_jdk16x_version() {
    return current().compare_major(6) == 0;

  static bool is_jdk17x_version() {
    return current().compare_major(7) == 0;

  static bool is_gte_jdk13x_version() {
    return current().compare_major(3) >= 0;

  static bool is_gte_jdk14x_version() {
    return current().compare_major(4) >= 0;

  static bool is_gte_jdk15x_version() {
    return current().compare_major(5) >= 0;

  static bool is_gte_jdk16x_version() {
    return current().compare_major(6) >= 0;

  static bool is_gte_jdk17x_version() {
    return current().compare_major(7) >= 0;