1// Copyright 2010 the V8 project authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5// The routines exported by this module are subtle. If you use them, even if 6// you get the code right, it will depend on careful reasoning about atomicity 7// and memory ordering; it will be less readable, and harder to maintain. If 8// you plan to use these routines, you should have a good reason, such as solid 9// evidence that performance would otherwise suffer, or there being no 10// alternative. You should assume only properties explicitly guaranteed by the 11// specifications in this file. You are almost certainly _not_ writing code 12// just for the x86; if you assume x86 semantics, x86 hardware bugs and 13// implementations on other archtectures will cause your code to break. If you 14// do not know what you are doing, avoid these routines, and use a Mutex. 15// 16// It is incorrect to make direct assignments to/from an atomic variable. 17// You should use one of the Load or Store routines. The NoBarrier 18// versions are provided when no barriers are needed: 19// NoBarrier_Store() 20// NoBarrier_Load() 21// Although there are currently no compiler enforcement, you are encouraged 22// to use these. 23// 24 25#ifndef V8_BASE_ATOMICOPS_H_ 26#define V8_BASE_ATOMICOPS_H_ 27 28#include "include/v8stdint.h" 29#include "src/base/build_config.h" 30 31#if defined(_WIN32) && defined(V8_HOST_ARCH_64_BIT) 32// windows.h #defines this (only on x64). This causes problems because the 33// public API also uses MemoryBarrier at the public name for this fence. So, on 34// X64, undef it, and call its documented 35// (http://msdn.microsoft.com/en-us/library/windows/desktop/ms684208.aspx) 36// implementation directly. 37#undef MemoryBarrier 38#endif 39 40namespace v8 { 41namespace base { 42 43typedef char Atomic8; 44typedef int32_t Atomic32; 45#ifdef V8_HOST_ARCH_64_BIT 46// We need to be able to go between Atomic64 and AtomicWord implicitly. This 47// means Atomic64 and AtomicWord should be the same type on 64-bit. 48#if defined(__ILP32__) 49typedef int64_t Atomic64; 50#else 51typedef intptr_t Atomic64; 52#endif 53#endif 54 55// Use AtomicWord for a machine-sized pointer. It will use the Atomic32 or 56// Atomic64 routines below, depending on your architecture. 57typedef intptr_t AtomicWord; 58 59// Atomically execute: 60// result = *ptr; 61// if (*ptr == old_value) 62// *ptr = new_value; 63// return result; 64// 65// I.e., replace "*ptr" with "new_value" if "*ptr" used to be "old_value". 66// Always return the old value of "*ptr" 67// 68// This routine implies no memory barriers. 69Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr, 70 Atomic32 old_value, 71 Atomic32 new_value); 72 73// Atomically store new_value into *ptr, returning the previous value held in 74// *ptr. This routine implies no memory barriers. 75Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr, Atomic32 new_value); 76 77// Atomically increment *ptr by "increment". Returns the new value of 78// *ptr with the increment applied. This routine implies no memory barriers. 79Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, Atomic32 increment); 80 81Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr, 82 Atomic32 increment); 83 84// These following lower-level operations are typically useful only to people 85// implementing higher-level synchronization operations like spinlocks, 86// mutexes, and condition-variables. They combine CompareAndSwap(), a load, or 87// a store with appropriate memory-ordering instructions. "Acquire" operations 88// ensure that no later memory access can be reordered ahead of the operation. 89// "Release" operations ensure that no previous memory access can be reordered 90// after the operation. "Barrier" operations have both "Acquire" and "Release" 91// semantics. A MemoryBarrier() has "Barrier" semantics, but does no memory 92// access. 93Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr, 94 Atomic32 old_value, 95 Atomic32 new_value); 96Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr, 97 Atomic32 old_value, 98 Atomic32 new_value); 99 100void MemoryBarrier(); 101void NoBarrier_Store(volatile Atomic8* ptr, Atomic8 value); 102void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value); 103void Acquire_Store(volatile Atomic32* ptr, Atomic32 value); 104void Release_Store(volatile Atomic32* ptr, Atomic32 value); 105 106Atomic8 NoBarrier_Load(volatile const Atomic8* ptr); 107Atomic32 NoBarrier_Load(volatile const Atomic32* ptr); 108Atomic32 Acquire_Load(volatile const Atomic32* ptr); 109Atomic32 Release_Load(volatile const Atomic32* ptr); 110 111// 64-bit atomic operations (only available on 64-bit processors). 112#ifdef V8_HOST_ARCH_64_BIT 113Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr, 114 Atomic64 old_value, 115 Atomic64 new_value); 116Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr, Atomic64 new_value); 117Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment); 118Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment); 119 120Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr, 121 Atomic64 old_value, 122 Atomic64 new_value); 123Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr, 124 Atomic64 old_value, 125 Atomic64 new_value); 126void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value); 127void Acquire_Store(volatile Atomic64* ptr, Atomic64 value); 128void Release_Store(volatile Atomic64* ptr, Atomic64 value); 129Atomic64 NoBarrier_Load(volatile const Atomic64* ptr); 130Atomic64 Acquire_Load(volatile const Atomic64* ptr); 131Atomic64 Release_Load(volatile const Atomic64* ptr); 132#endif // V8_HOST_ARCH_64_BIT 133 134} } // namespace v8::base 135 136// Include our platform specific implementation. 137#if defined(THREAD_SANITIZER) 138#include "src/base/atomicops_internals_tsan.h" 139#elif defined(_MSC_VER) && (V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64) 140#include "src/base/atomicops_internals_x86_msvc.h" 141#elif defined(__APPLE__) 142#include "src/base/atomicops_internals_mac.h" 143#elif defined(__GNUC__) && V8_HOST_ARCH_ARM64 144#include "src/base/atomicops_internals_arm64_gcc.h" 145#elif defined(__GNUC__) && V8_HOST_ARCH_ARM 146#include "src/base/atomicops_internals_arm_gcc.h" 147#elif defined(__GNUC__) && (V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64) 148#include "src/base/atomicops_internals_x86_gcc.h" 149#elif defined(__GNUC__) && V8_HOST_ARCH_MIPS 150#include "src/base/atomicops_internals_mips_gcc.h" 151#elif defined(__GNUC__) && V8_HOST_ARCH_MIPS64 152#include "src/base/atomicops_internals_mips64_gcc.h" 153#else 154#error "Atomic operations are not supported on your platform" 155#endif 156 157// On some platforms we need additional declarations to make 158// AtomicWord compatible with our other Atomic* types. 159#if defined(__APPLE__) || defined(__OpenBSD__) 160#include "src/base/atomicops_internals_atomicword_compat.h" 161#endif 162 163#endif // V8_BASE_ATOMICOPS_H_ 164