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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
// This file is an internal atomic implementation, use
// base/atomicops.h instead.
//
// This is a very slow fallback implementation of atomic operations
// that uses a mutex instead of atomic instructions.
//
// (NB: a small "optimization" here would be using a spinlock instead
// of a blocking mutex, but it's probably not worth the time.)
#ifndef base_atomicops_internals_mutex_h
#define base_atomicops_internals_mutex_h
#include "base/lock.h"
namespace base {
namespace subtle {
extern Lock gAtomicsMutex;
template<typename T>
T Locked_CAS(volatile T* ptr, T old_value, T new_value) {
AutoLock _(gAtomicsMutex);
T current_value = *ptr;
if (current_value == old_value)
*ptr = new_value;
return current_value;
}
template<typename T>
T Locked_AtomicExchange(volatile T* ptr, T new_value) {
AutoLock _(gAtomicsMutex);
T current_value = *ptr;
*ptr = new_value;
return current_value;
}
template<typename T>
T Locked_AtomicIncrement(volatile T* ptr, T increment) {
AutoLock _(gAtomicsMutex);
return *ptr += increment;
}
template<typename T>
void Locked_Store(volatile T* ptr, T value) {
AutoLock _(gAtomicsMutex);
*ptr = value;
}
template<typename T>
T Locked_Load(volatile const T* ptr) {
AutoLock _(gAtomicsMutex);
return *ptr;
}
inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
return Locked_CAS(ptr, old_value, new_value);
}
inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
Atomic32 new_value) {
return Locked_AtomicExchange(ptr, new_value);
}
inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
Atomic32 increment) {
return Locked_AtomicIncrement(ptr, increment);
}
inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
Atomic32 increment) {
return Locked_AtomicIncrement(ptr, increment);
}
inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
return Locked_CAS(ptr, old_value, new_value);
}
inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
return Locked_CAS(ptr, old_value, new_value);
}
inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
return Locked_Store(ptr, value);
}
inline void MemoryBarrier() {
AutoLock _(gAtomicsMutex);
// lock/unlock work as a barrier here
}
inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
return Locked_Store(ptr, value);
}
inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
return Locked_Store(ptr, value);
}
inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
return Locked_Load(ptr);
}
inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
return NoBarrier_Load(ptr);
}
inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
return Locked_Load(ptr);
}
#ifdef ARCH_CPU_64_BITS
inline Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,
Atomic64 old_value,
Atomic64 new_value) {
return Locked_CAS(ptr, old_value, new_value);
}
inline Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr,
Atomic64 new_value) {
return Locked_AtomicExchange(ptr, new_value);
}
inline Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr,
Atomic64 increment) {
return Locked_AtomicIncrement(ptr, increment);
}
inline Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr,
Atomic64 increment) {
return Locked_AtomicIncrement(ptr, increment);
}
inline void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value) {
return Locked_Store(ptr, value);
}
inline Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,
Atomic64 old_value,
Atomic64 new_value) {
return Locked_CAS(ptr, old_value, new_value);
}
inline void Acquire_Store(volatile Atomic64* ptr, Atomic64 value) {
return Locked_Store(ptr, value);
}
inline void Release_Store(volatile Atomic64* ptr, Atomic64 value) {
return Locked_Store(ptr, value);
}
inline Atomic64 NoBarrier_Load(volatile const Atomic64* ptr) {
return Locked_Load(ptr);
}
inline Atomic64 Acquire_Load(volatile const Atomic64* ptr) {
return Locked_Load(ptr);
}
inline Atomic64 Release_Load(volatile const Atomic64* ptr) {
return Locked_Load(ptr);
}
#endif // ARCH_CPU_64_BITS
#ifdef OS_MACOSX
// From atomicops_internals_x86_macosx.h:
//
// MacOS uses long for intptr_t, AtomicWord and Atomic32 are always
// different on the Mac, even when they are the same size. We need
// to explicitly cast from AtomicWord to Atomic32/64 to implement
// the AtomicWord interface.
inline AtomicWord NoBarrier_CompareAndSwap(volatile AtomicWord* ptr,
AtomicWord old_value,
AtomicWord new_value) {
return Locked_CAS(ptr, old_value, new_value);
}
inline AtomicWord NoBarrier_AtomicExchange(volatile AtomicWord* ptr,
AtomicWord new_value) {
return Locked_AtomicExchange(ptr, new_value);
}
inline AtomicWord NoBarrier_AtomicIncrement(volatile AtomicWord* ptr,
AtomicWord increment) {
return Locked_AtomicIncrement(ptr, increment);
}
inline AtomicWord Barrier_AtomicIncrement(volatile AtomicWord* ptr,
AtomicWord increment) {
return Locked_AtomicIncrement(ptr, increment);
}
inline AtomicWord Acquire_CompareAndSwap(volatile AtomicWord* ptr,
AtomicWord old_value,
AtomicWord new_value) {
return Locked_CAS(ptr, old_value, new_value);
}
inline AtomicWord Release_CompareAndSwap(volatile AtomicWord* ptr,
AtomicWord old_value,
AtomicWord new_value) {
return Locked_CAS(ptr, old_value, new_value);
}
inline void NoBarrier_Store(volatile AtomicWord *ptr, AtomicWord value) {
return Locked_Store(ptr, value);
}
inline void Acquire_Store(volatile AtomicWord* ptr, AtomicWord value) {
return Locked_Store(ptr, value);
}
inline void Release_Store(volatile AtomicWord* ptr, AtomicWord value) {
return Locked_Store(ptr, value);
}
inline AtomicWord NoBarrier_Load(volatile const AtomicWord *ptr) {
return Locked_Load(ptr);
}
inline AtomicWord Acquire_Load(volatile const AtomicWord* ptr) {
return Locked_Load(ptr);
}
inline AtomicWord Release_Load(volatile const AtomicWord* ptr) {
return Locked_Load(ptr);
}
#endif // OS_MACOSX
} // namespace subtle
} // namespace base
#endif // base_atomicops_internals_mutex_h
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