1 /*
   2  * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
   3  * Copyright (c) 2019, Google and/or its affiliates. All rights reserved.
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This code is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 only, as
   8  * published by the Free Software Foundation.
   9  *
  10  * This code is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * version 2 for more details (a copy is included in the LICENSE file that
  14  * accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License version
  17  * 2 along with this work; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  19  *
  20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  21  * or visit www.oracle.com if you need additional information or have any
  22  * questions.
  23  *
  24  */
  25 
  26 #ifndef SHARE_GC_G1_G1EPOCHUPDATER_INLINE_HPP
  27 #define SHARE_GC_G1_G1EPOCHUPDATER_INLINE_HPP
  28 
  29 // #include "classfile/javaClasses.hpp"
  30 #include "gc/g1/g1EpochSynchronizer.hpp"
  31 #include "gc/g1/g1ThreadLocalData.hpp"
  32 // #include "logging/log.hpp"
  33 #include "memory/allocation.hpp"
  34 #include "runtime/atomic.hpp"
  35 #include "runtime/safepoint.hpp"
  36 #include "runtime/thread.hpp"
  37 
  38 class JavaThread;
  39 
  40 class G1EpochUpdater : public AllStatic {
  41 
  42   static inline void update_epoch_internal(Thread* thread) {
  43     // We must not update epoch at a safepoint, in order to avoid
  44     // atomicity violation with resetting epoch at a safepoint.
  45     assert_not_at_safepoint();
  46     assert(thread->is_Java_thread(), "must be a Java thread");
  47     uintx global_epoch = G1EpochSynchronizer::global_epoch();
  48     volatile uintx& local_epoch = G1ThreadLocalData::epoch(thread);
  49     assert(Atomic::load_acquire(&local_epoch) <= global_epoch, "Epoch overflow");
  50     Atomic::release_store(&local_epoch, global_epoch);
  51     // log_info(gc, handshake)("Thread#" PTR_FORMAT ".epoch=" UINTX_FORMAT,
  52     //    p2i(thread), global_epoch);
  53     // log_info(gc, handshake)("Thread#" INT64_FORMAT ".epoch=" UINTX_FORMAT,
  54     //    (int64_t)java_lang_Thread::thread_id(thread->threadObj()), global_epoch);
  55   }
  56 
  57 public:
  58   static inline void update_epoch_self(Thread* thread) {
  59     assert(thread == Thread::current(), "epoch is updated by a remote thread");
  60     update_epoch_internal(thread);
  61   }
  62 
  63   static inline void update_epoch_self_or_other(Thread* thread) {
  64     update_epoch_internal(thread);
  65   }
  66 };
  67 
  68 #endif // SHARE_GC_G1_G1EPOCHUPDATER_INLINE_HPP