mirror of
https://github.com/klzgrad/naiveproxy.git
synced 2024-11-24 06:16:30 +03:00
162 lines
6.7 KiB
C++
162 lines
6.7 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file.
|
|
|
|
// For atomic operations on reference counts, see atomic_refcount.h.
|
|
// For atomic operations on sequence numbers, see atomic_sequence_num.h.
|
|
|
|
// The routines exported by this module are subtle. If you use them, even if
|
|
// you get the code right, it will depend on careful reasoning about atomicity
|
|
// and memory ordering; it will be less readable, and harder to maintain. If
|
|
// you plan to use these routines, you should have a good reason, such as solid
|
|
// evidence that performance would otherwise suffer, or there being no
|
|
// alternative. You should assume only properties explicitly guaranteed by the
|
|
// specifications in this file. You are almost certainly _not_ writing code
|
|
// just for the x86; if you assume x86 semantics, x86 hardware bugs and
|
|
// implementations on other archtectures will cause your code to break. If you
|
|
// do not know what you are doing, avoid these routines, and use a Mutex.
|
|
//
|
|
// It is incorrect to make direct assignments to/from an atomic variable.
|
|
// You should use one of the Load or Store routines. The NoBarrier
|
|
// versions are provided when no barriers are needed:
|
|
// NoBarrier_Store()
|
|
// NoBarrier_Load()
|
|
// Although there are currently no compiler enforcement, you are encouraged
|
|
// to use these.
|
|
//
|
|
|
|
#ifndef BASE_ATOMICOPS_H_
|
|
#define BASE_ATOMICOPS_H_
|
|
|
|
#include <stdint.h>
|
|
|
|
// Small C++ header which defines implementation specific macros used to
|
|
// identify the STL implementation.
|
|
// - libc++: captures __config for _LIBCPP_VERSION
|
|
// - libstdc++: captures bits/c++config.h for __GLIBCXX__
|
|
#include <cstddef>
|
|
|
|
#include "base/base_export.h"
|
|
#include "build/build_config.h"
|
|
|
|
#if defined(OS_WIN) && defined(ARCH_CPU_64_BITS)
|
|
// windows.h #defines this (only on x64). This causes problems because the
|
|
// public API also uses MemoryBarrier at the public name for this fence. So, on
|
|
// X64, undef it, and call its documented
|
|
// (http://msdn.microsoft.com/en-us/library/windows/desktop/ms684208.aspx)
|
|
// implementation directly.
|
|
#undef MemoryBarrier
|
|
#endif
|
|
|
|
namespace base {
|
|
namespace subtle {
|
|
|
|
typedef int32_t Atomic32;
|
|
#ifdef ARCH_CPU_64_BITS
|
|
// We need to be able to go between Atomic64 and AtomicWord implicitly. This
|
|
// means Atomic64 and AtomicWord should be the same type on 64-bit.
|
|
#if defined(__ILP32__) || defined(OS_NACL)
|
|
// NaCl's intptr_t is not actually 64-bits on 64-bit!
|
|
// http://code.google.com/p/nativeclient/issues/detail?id=1162
|
|
typedef int64_t Atomic64;
|
|
#else
|
|
typedef intptr_t Atomic64;
|
|
#endif
|
|
#endif
|
|
|
|
// Use AtomicWord for a machine-sized pointer. It will use the Atomic32 or
|
|
// Atomic64 routines below, depending on your architecture.
|
|
typedef intptr_t AtomicWord;
|
|
|
|
// Atomically execute:
|
|
// result = *ptr;
|
|
// if (*ptr == old_value)
|
|
// *ptr = new_value;
|
|
// return result;
|
|
//
|
|
// I.e., replace "*ptr" with "new_value" if "*ptr" used to be "old_value".
|
|
// Always return the old value of "*ptr"
|
|
//
|
|
// This routine implies no memory barriers.
|
|
Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
|
|
Atomic32 old_value,
|
|
Atomic32 new_value);
|
|
|
|
// Atomically store new_value into *ptr, returning the previous value held in
|
|
// *ptr. This routine implies no memory barriers.
|
|
Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr, Atomic32 new_value);
|
|
|
|
// Atomically increment *ptr by "increment". Returns the new value of
|
|
// *ptr with the increment applied. This routine implies no memory barriers.
|
|
Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, Atomic32 increment);
|
|
|
|
Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
|
|
Atomic32 increment);
|
|
|
|
// These following lower-level operations are typically useful only to people
|
|
// implementing higher-level synchronization operations like spinlocks,
|
|
// mutexes, and condition-variables. They combine CompareAndSwap(), a load, or
|
|
// a store with appropriate memory-ordering instructions. "Acquire" operations
|
|
// ensure that no later memory access can be reordered ahead of the operation.
|
|
// "Release" operations ensure that no previous memory access can be reordered
|
|
// after the operation. "Barrier" operations have both "Acquire" and "Release"
|
|
// semantics. A MemoryBarrier() has "Barrier" semantics, but does no memory
|
|
// access.
|
|
Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
|
|
Atomic32 old_value,
|
|
Atomic32 new_value);
|
|
Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
|
|
Atomic32 old_value,
|
|
Atomic32 new_value);
|
|
|
|
void MemoryBarrier();
|
|
void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value);
|
|
void Acquire_Store(volatile Atomic32* ptr, Atomic32 value);
|
|
void Release_Store(volatile Atomic32* ptr, Atomic32 value);
|
|
|
|
Atomic32 NoBarrier_Load(volatile const Atomic32* ptr);
|
|
Atomic32 Acquire_Load(volatile const Atomic32* ptr);
|
|
Atomic32 Release_Load(volatile const Atomic32* ptr);
|
|
|
|
// 64-bit atomic operations (only available on 64-bit processors).
|
|
#ifdef ARCH_CPU_64_BITS
|
|
Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,
|
|
Atomic64 old_value,
|
|
Atomic64 new_value);
|
|
Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr, Atomic64 new_value);
|
|
Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment);
|
|
Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment);
|
|
|
|
Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,
|
|
Atomic64 old_value,
|
|
Atomic64 new_value);
|
|
Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,
|
|
Atomic64 old_value,
|
|
Atomic64 new_value);
|
|
void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value);
|
|
void Acquire_Store(volatile Atomic64* ptr, Atomic64 value);
|
|
void Release_Store(volatile Atomic64* ptr, Atomic64 value);
|
|
Atomic64 NoBarrier_Load(volatile const Atomic64* ptr);
|
|
Atomic64 Acquire_Load(volatile const Atomic64* ptr);
|
|
Atomic64 Release_Load(volatile const Atomic64* ptr);
|
|
#endif // ARCH_CPU_64_BITS
|
|
|
|
} // namespace subtle
|
|
} // namespace base
|
|
|
|
#if defined(OS_WIN)
|
|
// TODO(jfb): Try to use base/atomicops_internals_portable.h everywhere.
|
|
// https://crbug.com/559247.
|
|
# include "base/atomicops_internals_x86_msvc.h"
|
|
#else
|
|
# include "base/atomicops_internals_portable.h"
|
|
#endif
|
|
|
|
// On some platforms we need additional declarations to make
|
|
// AtomicWord compatible with our other Atomic* types.
|
|
#if defined(OS_MACOSX) || defined(OS_OPENBSD)
|
|
#include "base/atomicops_internals_atomicword_compat.h"
|
|
#endif
|
|
|
|
#endif // BASE_ATOMICOPS_H_
|