view src/hotspot/share/logging/logOutputList.hpp @ 54526:ee29b516a36a

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author jlaskey
date Wed, 23 Jan 2019 16:09:20 -0400
parents 601146c66cad
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 * Copyright (c) 2015, 2019, 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 "logging/logLevel.hpp"
#include "memory/allocation.hpp"
#include "utilities/globalDefinitions.hpp"

class LogOutput;

// Data structure to keep track of log outputs for a given tagset.
// Essentially a sorted linked list going from error level outputs
// to outputs of finer levels. Keeps an index from each level to
// the first node in the list for the corresponding level.
// This allows a log message on, for example, info level to jump
// straight into the list where the first info level output can
// be found. The log message will then be printed on that output,
// as well as all outputs in nodes that follow in the list (which
// can be additional info level outputs and/or debug and trace outputs).
// Each instance keeps track of the number of current readers of the list.
// To remove a node from the list the node must first be unlinked,
// and the memory for that node can be freed whenever the removing
// thread observes an active reader count of 0 (after unlinking it).
class LogOutputList {
  struct LogOutputNode : public CHeapObj<mtLogging> {
    LogOutput*      _value;
    LogOutputNode*  _next;
    LogLevelType    _level;

  LogOutputNode*  _level_start[LogLevel::Count];
  volatile jint   _active_readers;

  LogOutputNode* find(const LogOutput* output) const;
  void remove_output(LogOutputNode* node);
  void add_output(LogOutput* output, LogLevelType level);
  void update_output_level(LogOutputNode* node, LogLevelType level);

  // Bookkeeping functions to keep track of number of active readers/iterators for the list.
  jint increase_readers();
  jint decrease_readers();
  void wait_until_no_readers() const;

  LogOutputList() : _active_readers(0) {
    for (size_t i = 0; i < LogLevel::Count; i++) {
      _level_start[i] = NULL;

  // Test if the outputlist has an output for the given level.
  bool is_level(LogLevelType level) const {
    return _level_start[level] != NULL;

  LogLevelType level_for(const LogOutput* output) const {
    LogOutputNode* node = this->find(output);
    if (node == NULL) {
      return LogLevel::Off;
    return node->_level;

  // Set (add/update/remove) the output to the specified level.
  void set_output_level(LogOutput* output, LogLevelType level);

  class Iterator {
    friend class LogOutputList;
    LogOutputNode*  _current;
    LogOutputList*  _list;
    Iterator(LogOutputList* list, LogOutputNode* start) : _current(start), _list(list) {

    ~Iterator() {

    LogOutput* operator*() {
      return _current->_value;

    void operator++(int) {
      _current = _current->_next;

    bool operator!=(const LogOutputNode *ref) const {
      return _current != ref;

    LogLevelType level() const {
      return _current->_level;

  Iterator iterator(LogLevelType level = LogLevel::Last) {
    return Iterator(this, _level_start[level]);

  LogOutputNode* end() const {
    return NULL;