JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
 * Copyright 2007, 2008, 2011, 2015, Red Hat, Inc.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * 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
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#ifndef OS_CPU_LINUX_ZERO_ATOMIC_LINUX_ZERO_HPP
#define OS_CPU_LINUX_ZERO_ATOMIC_LINUX_ZERO_HPP

#include "runtime/os.hpp"

// Implementation of class atomic

template<size_t byte_size>
struct Atomic::PlatformAdd
  : Atomic::AddAndFetch<Atomic::PlatformAdd<byte_size> >
{
  template<typename D, typename I>
  D add_and_fetch(D volatile* dest, I add_value, atomic_memory_order order) const;
};

template<>
template<typename D, typename I>
inline D Atomic::PlatformAdd<4>::add_and_fetch(D volatile* dest, I add_value,
                                               atomic_memory_order order) const {
  STATIC_ASSERT(4 == sizeof(I));
  STATIC_ASSERT(4 == sizeof(D));

  return __sync_add_and_fetch(dest, add_value);
}

template<>
template<typename D, typename I>
inline D Atomic::PlatformAdd<8>::add_and_fetch(D volatile* dest, I add_value,
                                               atomic_memory_order order) const {
  STATIC_ASSERT(8 == sizeof(I));
  STATIC_ASSERT(8 == sizeof(D));
  return __sync_add_and_fetch(dest, add_value);
}

template<>
template<typename T>
inline T Atomic::PlatformXchg<4>::operator()(T volatile* dest,
                                             T exchange_value,
                                             atomic_memory_order order) const {
  STATIC_ASSERT(4 == sizeof(T));
  // __sync_lock_test_and_set is a bizarrely named atomic exchange
  // operation.  Note that some platforms only support this with the
  // limitation that the only valid value to store is the immediate
  // constant 1.  There is a test for this in JNI_CreateJavaVM().
  T result = __sync_lock_test_and_set (dest, exchange_value);
  // All atomic operations are expected to be full memory barriers
  // (see atomic.hpp). However, __sync_lock_test_and_set is not
  // a full memory barrier, but an acquire barrier. Hence, this added
  // barrier.
  __sync_synchronize();
  return result;
}

template<>
template<typename T>
inline T Atomic::PlatformXchg<8>::operator()(T volatile* dest,
                                             T exchange_value,
                                             atomic_memory_order order) const {
  STATIC_ASSERT(8 == sizeof(T));
  T result = __sync_lock_test_and_set (dest, exchange_value);
  __sync_synchronize();
  return result;
}

// No direct support for cmpxchg of bytes; emulate using int.
template<>
struct Atomic::PlatformCmpxchg<1> : Atomic::CmpxchgByteUsingInt {};

template<>
template<typename T>
inline T Atomic::PlatformCmpxchg<4>::operator()(T volatile* dest,
                                                T compare_value,
                                                T exchange_value,
                                                atomic_memory_order order) const {
  STATIC_ASSERT(4 == sizeof(T));
  return __sync_val_compare_and_swap(dest, compare_value, exchange_value);
}

template<>
template<typename T>
inline T Atomic::PlatformCmpxchg<8>::operator()(T volatile* dest,
                                                T compare_value,
                                                T exchange_value,
                                                atomic_memory_order order) const {
  STATIC_ASSERT(8 == sizeof(T));
  return __sync_val_compare_and_swap(dest, compare_value, exchange_value);
}

template<>
template<typename T>
inline T Atomic::PlatformLoad<8>::operator()(T const volatile* src) const {
  STATIC_ASSERT(8 == sizeof(T));
  volatile int64_t dest;

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