1 /*
   2  * Copyright (c) 2015, 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 "runtime/atomic.hpp"
  30 #include "utilities/globalDefinitions.hpp"
  31 
  32 class LogOutput;
  33 
  34 // Data structure to keep track of log outputs for a given tagset.
  35 // Essentially a sorted linked list going from error level outputs
  36 // to outputs of finer levels. Keeps an index from each level to
  37 // the first node in the list for the corresponding level.
  38 // This allows a log message on, for example, info level to jump
  39 // straight into the list where the first info level output can
  40 // be found. The log message will then be printed on that output,
  41 // as well as all outputs in nodes that follow in the list (which
  42 // can be additional info level outputs and/or debug and trace outputs).
  43 //
  44 // Each instance keeps track of the number of current readers of the list.
  45 // To remove a node from the list the node must first be unlinked,
  46 // and the memory for that node can be freed whenever the removing
  47 // thread observes an active reader count of 0 (after unlinking it).
  48 class LogOutputList VALUE_OBJ_CLASS_SPEC {
  49  private:
  50   struct LogOutputNode : public CHeapObj<mtLogging> {
  51     LogOutput*      _value;
  52     LogOutputNode*  _next;
  53     LogLevelType    _level;
  54   };
  55 
  56   LogOutputNode*  _level_start[LogLevel::Count];
  57   volatile jint   _active_readers;
  58 
  59   LogOutputNode* find(const LogOutput* output) const;
  60   void remove_output(LogOutputNode* node);
  61   void add_output(LogOutput* output, LogLevelType level);
  62   void update_output_level(LogOutputNode* node, LogLevelType level);
  63 
  64  public:
  65   LogOutputList() : _active_readers(0) {
  66     for (size_t i = 0; i < LogLevel::Count; i++) {
  67       _level_start[i] = NULL;
  68     }
  69   }
  70 
  71   // Test if the outputlist has an output for the given level.
  72   bool is_level(LogLevelType level) const {
  73     return _level_start[level] != NULL;
  74   }
  75 
  76   LogLevelType level_for(const LogOutput* output) const {
  77     LogOutputNode* node = this->find(output);
  78     if (node == NULL) {
  79       return LogLevel::Off;
  80     }
  81     return node->_level;
  82   }
  83 
  84   // Set (add/update/remove) the output to the specified level.
  85   void set_output_level(LogOutput* output, LogLevelType level);
  86 
  87   // Bookkeeping functions to keep track of number of active readers/iterators for the list.
  88   jint increase_readers();
  89   jint decrease_readers();
  90   void wait_until_no_readers() const;
  91 
  92   class Iterator VALUE_OBJ_CLASS_SPEC {
  93     friend class LogOutputList;
  94    private:
  95     LogOutputNode*  _current;
  96     LogOutputList*  _list;
  97     Iterator(LogOutputList* list, LogOutputNode* start) : _current(start), _list(list) {
  98     }
  99 
 100    public:
 101     ~Iterator() {
 102       _list->decrease_readers();
 103     }
 104 
 105     LogOutput* operator*() {
 106       return _current->_value;
 107     }
 108 
 109     void operator++(int) {
 110       _current = _current->_next;
 111     }
 112 
 113     bool operator!=(const LogOutputNode *ref) const {
 114       return _current != ref;
 115     }
 116   };
 117 
 118   Iterator iterator(LogLevelType level = LogLevel::Last) {
 119     increase_readers();
 120     return Iterator(this, _level_start[level]);
 121   }
 122 
 123   LogOutputNode* end() const {
 124     return NULL;
 125   }
 126 };
 127 
 128 #endif // SHARE_VM_LOGGING_LOGOUTPUTLIST_HPP