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.
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.
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:
21 // Although there are currently no compiler enforcement, you are encouraged
25 #ifndef V8_BASE_ATOMICOPS_H_
26 #define V8_BASE_ATOMICOPS_H_
28 #include "include/v8stdint.h"
29 #include "src/base/build_config.h"
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.
44 typedef 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__)
49 typedef int64_t Atomic64;
51 typedef intptr_t Atomic64;
55 // Use AtomicWord for a machine-sized pointer. It will use the Atomic32 or
56 // Atomic64 routines below, depending on your architecture.
57 typedef intptr_t AtomicWord;
59 // Atomically execute:
61 // if (*ptr == old_value)
65 // I.e., replace "*ptr" with "new_value" if "*ptr" used to be "old_value".
66 // Always return the old value of "*ptr"
68 // This routine implies no memory barriers.
69 Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
73 // Atomically store new_value into *ptr, returning the previous value held in
74 // *ptr. This routine implies no memory barriers.
75 Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr, Atomic32 new_value);
77 // Atomically increment *ptr by "increment". Returns the new value of
78 // *ptr with the increment applied. This routine implies no memory barriers.
79 Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, Atomic32 increment);
81 Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
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
93 Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
96 Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
100 void MemoryBarrier();
101 void NoBarrier_Store(volatile Atomic8* ptr, Atomic8 value);
102 void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value);
103 void Acquire_Store(volatile Atomic32* ptr, Atomic32 value);
104 void Release_Store(volatile Atomic32* ptr, Atomic32 value);
106 Atomic8 NoBarrier_Load(volatile const Atomic8* ptr);
107 Atomic32 NoBarrier_Load(volatile const Atomic32* ptr);
108 Atomic32 Acquire_Load(volatile const Atomic32* ptr);
109 Atomic32 Release_Load(volatile const Atomic32* ptr);
111 // 64-bit atomic operations (only available on 64-bit processors).
112 #ifdef V8_HOST_ARCH_64_BIT
113 Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,
116 Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr, Atomic64 new_value);
117 Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment);
118 Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment);
120 Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,
123 Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,
126 void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value);
127 void Acquire_Store(volatile Atomic64* ptr, Atomic64 value);
128 void Release_Store(volatile Atomic64* ptr, Atomic64 value);
129 Atomic64 NoBarrier_Load(volatile const Atomic64* ptr);
130 Atomic64 Acquire_Load(volatile const Atomic64* ptr);
131 Atomic64 Release_Load(volatile const Atomic64* ptr);
132 #endif // V8_HOST_ARCH_64_BIT
134 } } // namespace v8::base
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"
154 #error "Atomic operations are not supported on your platform"
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"
163 #endif // V8_BASE_ATOMICOPS_H_