1 /*
  2  * Copyright (c) 2016, 2021, 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 
 25 #ifndef SHARE_JFR_RECORDER_CHECKPOINT_TYPES_TRACEID_JFRTRACEIDEPOCH_HPP
 26 #define SHARE_JFR_RECORDER_CHECKPOINT_TYPES_TRACEID_JFRTRACEIDEPOCH_HPP
 27 
 28 #include "jfr/utilities/jfrSignal.hpp"
 29 #include "jfr/utilities/jfrTypes.hpp"
 30 #include "memory/allocation.hpp"
 31 #include "runtime/atomic.hpp"
 32 
 33 #define BIT                                  1
 34 #define METHOD_BIT                           (BIT << 2)
 35 #define EPOCH_0_SHIFT                        0
 36 #define EPOCH_1_SHIFT                        1
 37 #define EPOCH_0_BIT                          (BIT << EPOCH_0_SHIFT)
 38 #define EPOCH_1_BIT                          (BIT << EPOCH_1_SHIFT)
 39 #define EPOCH_0_METHOD_BIT                   (METHOD_BIT << EPOCH_0_SHIFT)
 40 #define EPOCH_1_METHOD_BIT                   (METHOD_BIT << EPOCH_1_SHIFT)
 41 #define METHOD_AND_CLASS_BITS                (METHOD_BIT | BIT)
 42 #define EPOCH_0_METHOD_AND_CLASS_BITS        (METHOD_AND_CLASS_BITS << EPOCH_0_SHIFT)
 43 #define EPOCH_1_METHOD_AND_CLASS_BITS        (METHOD_AND_CLASS_BITS << EPOCH_1_SHIFT)
 44 
 45  // Epoch alternation on each rotation allow for concurrent tagging.
 46  // The epoch shift happens only during a safepoint.
 47  //
 48  // _synchronizing is a transition state, the purpose of which is to
 49  // have JavaThreads that run _thread_in_native (i.e. Compiler threads)
 50  // respect the current epoch shift in-progress during the safepoint.
 51  //
 52  // _changed_tag_state == true signals an incremental modification to artifact tagging
 53  // (klasses, methods, CLDs, etc), purpose of which is to trigger collection of artifacts.
 54  //
 55 class JfrTraceIdEpoch : AllStatic {
 56   friend class JfrCheckpointManager;
 57  private:
 58   static JfrSignal _tag_state;
 59   static bool _epoch_state;
 60   static bool _synchronizing;
 61 
 62   static void begin_epoch_shift();
 63   static void end_epoch_shift();
 64 
 65  public:
 66   static bool epoch() {
 67     return _epoch_state;
 68   }
 69 
 70   static address epoch_address() {
 71     return (address)&_epoch_state;
 72   }
 73 
 74   static u1 current() {
 75     return _epoch_state ? (u1)1 : (u1)0;
 76   }
 77 
 78   static u1 previous() {
 79     return _epoch_state ? (u1)0 : (u1)1;
 80   }
 81 
 82   static bool is_synchronizing() {
 83     return Atomic::load_acquire(&_synchronizing);
 84   }
 85 
 86   static traceid this_epoch_bit() {
 87     return _epoch_state ? EPOCH_1_BIT : EPOCH_0_BIT;
 88   }
 89 
 90   static traceid previous_epoch_bit() {
 91     return _epoch_state ? EPOCH_0_BIT : EPOCH_1_BIT;
 92   }
 93 
 94   static traceid this_epoch_method_bit() {
 95     return _epoch_state ? EPOCH_1_METHOD_BIT : EPOCH_0_METHOD_BIT;
 96   }
 97 
 98   static traceid previous_epoch_method_bit() {
 99     return _epoch_state ? EPOCH_0_METHOD_BIT : EPOCH_1_METHOD_BIT;
100   }
101 
102   static traceid this_epoch_method_and_class_bits() {
103     return _epoch_state ? EPOCH_1_METHOD_AND_CLASS_BITS : EPOCH_0_METHOD_AND_CLASS_BITS;
104   }
105 
106   static traceid previous_epoch_method_and_class_bits() {
107     return _epoch_state ? EPOCH_0_METHOD_AND_CLASS_BITS : EPOCH_1_METHOD_AND_CLASS_BITS;
108   }
109 
110   static bool has_changed_tag_state() {
111     return _tag_state.is_signaled_with_reset();
112   }
113 
114   static bool has_changed_tag_state_no_reset() {
115     return _tag_state.is_signaled();
116   }
117 
118   static void set_changed_tag_state() {
119     _tag_state.signal();
120   }
121 
122   static address signal_address() {
123     return _tag_state.signaled_address();
124   }
125 };
126 
127 #endif // SHARE_JFR_RECORDER_CHECKPOINT_TYPES_TRACEID_JFRTRACEIDEPOCH_HPP