1 /*
   2  * Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 #ifndef SHARE_VM_LOGGING_LOGOUTPUTLIST_HPP
  25 #define SHARE_VM_LOGGING_LOGOUTPUTLIST_HPP
  26 
  27 #include "logging/logLevel.hpp"
  28 #include "memory/allocation.hpp"
  29 #include "utilities/globalDefinitions.hpp"
  30 
  31 class LogOutput;
  32 
  33 // Data structure to keep track of log outputs for a given tagset.
  34 // Essentially a sorted linked list going from error level outputs
  35 // to outputs of finer levels. Keeps an index from each level to
  36 // the first node in the list for the corresponding level.
  37 // This allows a log message on, for example, info level to jump
  38 // straight into the list where the first info level output can
  39 // be found. The log message will then be printed on that output,
  40 // as well as all outputs in nodes that follow in the list (which
  41 // can be additional info level outputs and/or debug and trace outputs).
  42 //
  43 // Each instance keeps track of the number of current readers of the list.
  44 // To remove a node from the list the node must first be unlinked,
  45 // and the memory for that node can be freed whenever the removing
  46 // thread observes an active reader count of 0 (after unlinking it).
  47 class LogOutputList {
  48  private:
  49   struct LogOutputNode : public CHeapObj<mtLogging> {
  50     LogOutput*      _value;
  51     LogOutputNode*  _next;
  52     LogLevelType    _level;
  53   };
  54 
  55   LogOutputNode*  _level_start[LogLevel::Count];
  56   volatile jint   _active_readers;
  57 
  58   LogOutputNode* find(const LogOutput* output) const;
  59   void remove_output(LogOutputNode* node);
  60   void add_output(LogOutput* output, LogLevelType level);
  61   void update_output_level(LogOutputNode* node, LogLevelType level);
  62 
  63   // Bookkeeping functions to keep track of number of active readers/iterators for the list.
  64   jint increase_readers();
  65   jint decrease_readers();
  66   void wait_until_no_readers() const;
  67 
  68  public:
  69   LogOutputList() : _active_readers(0) {
  70     for (size_t i = 0; i < LogLevel::Count; i++) {
  71       _level_start[i] = NULL;
  72     }
  73   }
  74 
  75   // Test if the outputlist has an output for the given level.
  76   bool is_level(LogLevelType level) const {
  77     return _level_start[level] != NULL;
  78   }
  79 
  80   LogLevelType level_for(const LogOutput* output) const {
  81     LogOutputNode* node = this->find(output);
  82     if (node == NULL) {
  83       return LogLevel::Off;
  84     }
  85     return node->_level;
  86   }
  87 
  88   // Set (add/update/remove) the output to the specified level.
  89   void set_output_level(LogOutput* output, LogLevelType level);
  90 
  91   class Iterator {
  92     friend class LogOutputList;
  93    private:
  94     LogOutputNode*  _current;
  95     LogOutputList*  _list;
  96     Iterator(LogOutputList* list, LogOutputNode* start) : _current(start), _list(list) {
  97     }
  98 
  99    public:
 100     ~Iterator() {
 101       _list->decrease_readers();
 102     }
 103 
 104     LogOutput* operator*() {
 105       return _current->_value;
 106     }
 107 
 108     void operator++(int) {
 109       _current = _current->_next;
 110     }
 111 
 112     bool operator!=(const LogOutputNode *ref) const {
 113       return _current != ref;
 114     }
 115 
 116     LogLevelType level() const {
 117       return _current->_level;
 118     }
 119   };
 120 
 121   Iterator iterator(LogLevelType level = LogLevel::Last) {
 122     increase_readers();
 123     return Iterator(this, _level_start[level]);
 124   }
 125 
 126   LogOutputNode* end() const {
 127     return NULL;
 128   }
 129 };
 130 
 131 #endif // SHARE_VM_LOGGING_LOGOUTPUTLIST_HPP