1// Protocol Buffers - Google's data interchange format 2// Copyright 2012 Google Inc. All rights reserved. 3// http://code.google.com/p/protobuf/ 4// 5// Redistribution and use in source and binary forms, with or without 6// modification, are permitted provided that the following conditions are 7// met: 8// 9// * Redistributions of source code must retain the above copyright 10// notice, this list of conditions and the following disclaimer. 11// * Redistributions in binary form must reproduce the above 12// copyright notice, this list of conditions and the following disclaimer 13// in the documentation and/or other materials provided with the 14// distribution. 15// * Neither the name of Google Inc. nor the names of its 16// contributors may be used to endorse or promote products derived from 17// this software without specific prior written permission. 18// 19// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31// The routines exported by this module are subtle. If you use them, even if 32// you get the code right, it will depend on careful reasoning about atomicity 33// and memory ordering; it will be less readable, and harder to maintain. If 34// you plan to use these routines, you should have a good reason, such as solid 35// evidence that performance would otherwise suffer, or there being no 36// alternative. You should assume only properties explicitly guaranteed by the 37// specifications in this file. You are almost certainly _not_ writing code 38// just for the x86; if you assume x86 semantics, x86 hardware bugs and 39// implementations on other archtectures will cause your code to break. If you 40// do not know what you are doing, avoid these routines, and use a Mutex. 41// 42// It is incorrect to make direct assignments to/from an atomic variable. 43// You should use one of the Load or Store routines. The NoBarrier 44// versions are provided when no barriers are needed: 45// NoBarrier_Store() 46// NoBarrier_Load() 47// Although there are currently no compiler enforcement, you are encouraged 48// to use these. 49 50// This header and the implementations for each platform (located in 51// atomicops_internals_*) must be kept in sync with the upstream code (V8). 52 53#ifndef GOOGLE_PROTOBUF_ATOMICOPS_H_ 54#define GOOGLE_PROTOBUF_ATOMICOPS_H_ 55 56// Don't include this file for people not concerned about thread safety. 57#ifndef GOOGLE_PROTOBUF_NO_THREAD_SAFETY 58 59#include <google/protobuf/stubs/platform_macros.h> 60 61namespace google { 62namespace protobuf { 63namespace internal { 64 65typedef int32 Atomic32; 66#ifdef GOOGLE_PROTOBUF_ARCH_64_BIT 67// We need to be able to go between Atomic64 and AtomicWord implicitly. This 68// means Atomic64 and AtomicWord should be the same type on 64-bit. 69#if defined(__ILP32__) || defined(GOOGLE_PROTOBUF_OS_NACL) 70// NaCl's intptr_t is not actually 64-bits on 64-bit! 71// http://code.google.com/p/nativeclient/issues/detail?id=1162 72typedef int64 Atomic64; 73#else 74typedef intptr_t Atomic64; 75#endif 76#endif 77 78// Use AtomicWord for a machine-sized pointer. It will use the Atomic32 or 79// Atomic64 routines below, depending on your architecture. 80typedef intptr_t AtomicWord; 81 82// Atomically execute: 83// result = *ptr; 84// if (*ptr == old_value) 85// *ptr = new_value; 86// return result; 87// 88// I.e., replace "*ptr" with "new_value" if "*ptr" used to be "old_value". 89// Always return the old value of "*ptr" 90// 91// This routine implies no memory barriers. 92Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr, 93 Atomic32 old_value, 94 Atomic32 new_value); 95 96// Atomically store new_value into *ptr, returning the previous value held in 97// *ptr. This routine implies no memory barriers. 98Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr, Atomic32 new_value); 99 100// Atomically increment *ptr by "increment". Returns the new value of 101// *ptr with the increment applied. This routine implies no memory barriers. 102Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, Atomic32 increment); 103 104Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr, 105 Atomic32 increment); 106 107// These following lower-level operations are typically useful only to people 108// implementing higher-level synchronization operations like spinlocks, 109// mutexes, and condition-variables. They combine CompareAndSwap(), a load, or 110// a store with appropriate memory-ordering instructions. "Acquire" operations 111// ensure that no later memory access can be reordered ahead of the operation. 112// "Release" operations ensure that no previous memory access can be reordered 113// after the operation. "Barrier" operations have both "Acquire" and "Release" 114// semantics. A MemoryBarrier() has "Barrier" semantics, but does no memory 115// access. 116Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr, 117 Atomic32 old_value, 118 Atomic32 new_value); 119Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr, 120 Atomic32 old_value, 121 Atomic32 new_value); 122 123void MemoryBarrier(); 124void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value); 125void Acquire_Store(volatile Atomic32* ptr, Atomic32 value); 126void Release_Store(volatile Atomic32* ptr, Atomic32 value); 127 128Atomic32 NoBarrier_Load(volatile const Atomic32* ptr); 129Atomic32 Acquire_Load(volatile const Atomic32* ptr); 130Atomic32 Release_Load(volatile const Atomic32* ptr); 131 132// 64-bit atomic operations (only available on 64-bit processors). 133#ifdef GOOGLE_PROTOBUF_ARCH_64_BIT 134Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr, 135 Atomic64 old_value, 136 Atomic64 new_value); 137Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr, Atomic64 new_value); 138Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment); 139Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment); 140 141Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr, 142 Atomic64 old_value, 143 Atomic64 new_value); 144Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr, 145 Atomic64 old_value, 146 Atomic64 new_value); 147void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value); 148void Acquire_Store(volatile Atomic64* ptr, Atomic64 value); 149void Release_Store(volatile Atomic64* ptr, Atomic64 value); 150Atomic64 NoBarrier_Load(volatile const Atomic64* ptr); 151Atomic64 Acquire_Load(volatile const Atomic64* ptr); 152Atomic64 Release_Load(volatile const Atomic64* ptr); 153#endif // GOOGLE_PROTOBUF_ARCH_64_BIT 154 155} // namespace internal 156} // namespace protobuf 157} // namespace google 158 159// Include our platform specific implementation. 160#define GOOGLE_PROTOBUF_ATOMICOPS_ERROR \ 161#error "Atomic operations are not supported on your platform" 162 163// ThreadSanitizer, http://clang.llvm.org/docs/ThreadSanitizer.html. 164#if defined(THREAD_SANITIZER) 165#include <google/protobuf/stubs/atomicops_internals_tsan.h> 166// MSVC. 167#elif defined(_MSC_VER) 168#if defined(GOOGLE_PROTOBUF_ARCH_IA32) || defined(GOOGLE_PROTOBUF_ARCH_X64) 169#include <google/protobuf/stubs/atomicops_internals_x86_msvc.h> 170#else 171GOOGLE_PROTOBUF_ATOMICOPS_ERROR 172#endif 173 174// Apple. 175#elif defined(GOOGLE_PROTOBUF_OS_APPLE) 176#include <google/protobuf/stubs/atomicops_internals_macosx.h> 177 178// GCC. 179#elif defined(__GNUC__) 180#if defined(GOOGLE_PROTOBUF_ARCH_IA32) || defined(GOOGLE_PROTOBUF_ARCH_X64) 181#include <google/protobuf/stubs/atomicops_internals_x86_gcc.h> 182#elif defined(GOOGLE_PROTOBUF_ARCH_ARM) 183#include <google/protobuf/stubs/atomicops_internals_arm_gcc.h> 184#elif defined(GOOGLE_PROTOBUF_ARCH_AARCH64) 185#include <google/protobuf/stubs/atomicops_internals_arm64_gcc.h> 186#elif defined(GOOGLE_PROTOBUF_ARCH_ARM_QNX) 187#include <google/protobuf/stubs/atomicops_internals_arm_qnx.h> 188#elif defined(GOOGLE_PROTOBUF_ARCH_MIPS) || defined(GOOGLE_PROTOBUF_ARCH_MIPS64) 189#include <google/protobuf/stubs/atomicops_internals_mips_gcc.h> 190#elif defined(__pnacl__) 191#include <google/protobuf/stubs/atomicops_internals_pnacl.h> 192#else 193GOOGLE_PROTOBUF_ATOMICOPS_ERROR 194#endif 195 196// Unknown. 197#else 198GOOGLE_PROTOBUF_ATOMICOPS_ERROR 199#endif 200 201// On some platforms we need additional declarations to make AtomicWord 202// compatible with our other Atomic* types. 203#if defined(GOOGLE_PROTOBUF_OS_APPLE) 204#include <google/protobuf/stubs/atomicops_internals_atomicword_compat.h> 205#endif 206 207#undef GOOGLE_PROTOBUF_ATOMICOPS_ERROR 208 209#endif // GOOGLE_PROTOBUF_NO_THREAD_SAFETY 210 211#endif // GOOGLE_PROTOBUF_ATOMICOPS_H_ 212