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 61 namespace google { 62 namespace protobuf { 63 namespace internal { 64 65 typedef 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(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 72 typedef int64 Atomic64; 73 #else 74 typedef 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. 80 typedef 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. 92 Atomic32 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. 98 Atomic32 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. 102 Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, Atomic32 increment); 103 104 Atomic32 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. 116 Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr, 117 Atomic32 old_value, 118 Atomic32 new_value); 119 Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr, 120 Atomic32 old_value, 121 Atomic32 new_value); 122 123 void MemoryBarrier(); 124 void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value); 125 void Acquire_Store(volatile Atomic32* ptr, Atomic32 value); 126 void Release_Store(volatile Atomic32* ptr, Atomic32 value); 127 128 Atomic32 NoBarrier_Load(volatile const Atomic32* ptr); 129 Atomic32 Acquire_Load(volatile const Atomic32* ptr); 130 Atomic32 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 134 Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr, 135 Atomic64 old_value, 136 Atomic64 new_value); 137 Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr, Atomic64 new_value); 138 Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment); 139 Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr, Atomic64 increment); 140 141 Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr, 142 Atomic64 old_value, 143 Atomic64 new_value); 144 Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr, 145 Atomic64 old_value, 146 Atomic64 new_value); 147 void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value); 148 void Acquire_Store(volatile Atomic64* ptr, Atomic64 value); 149 void Release_Store(volatile Atomic64* ptr, Atomic64 value); 150 Atomic64 NoBarrier_Load(volatile const Atomic64* ptr); 151 Atomic64 Acquire_Load(volatile const Atomic64* ptr); 152 Atomic64 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 // MSVC. 164 #if defined(_MSC_VER) 165 #if defined(GOOGLE_PROTOBUF_ARCH_IA32) || defined(GOOGLE_PROTOBUF_ARCH_X64) 166 #include <google/protobuf/stubs/atomicops_internals_x86_msvc.h> 167 #else 168 GOOGLE_PROTOBUF_ATOMICOPS_ERROR 169 #endif 170 171 // Apple. 172 #elif defined(GOOGLE_PROTOBUF_OS_APPLE) 173 #include <google/protobuf/stubs/atomicops_internals_macosx.h> 174 175 // GCC. 176 #elif defined(__GNUC__) 177 #if defined(GOOGLE_PROTOBUF_ARCH_IA32) || defined(GOOGLE_PROTOBUF_ARCH_X64) 178 #include <google/protobuf/stubs/atomicops_internals_x86_gcc.h> 179 #elif defined(GOOGLE_PROTOBUF_ARCH_ARM) 180 #include <google/protobuf/stubs/atomicops_internals_arm_gcc.h> 181 #elif defined(GOOGLE_PROTOBUF_ARCH_ARM_QNX) 182 #include <google/protobuf/stubs/atomicops_internals_arm_qnx.h> 183 #elif defined(GOOGLE_PROTOBUF_ARCH_MIPS) 184 #include <google/protobuf/stubs/atomicops_internals_mips_gcc.h> 185 #elif defined(__pnacl__) 186 #include <google/protobuf/stubs/atomicops_internals_pnacl.h> 187 #else 188 GOOGLE_PROTOBUF_ATOMICOPS_ERROR 189 #endif 190 191 // Unknown. 192 #else 193 GOOGLE_PROTOBUF_ATOMICOPS_ERROR 194 #endif 195 196 // On some platforms we need additional declarations to make AtomicWord 197 // compatible with our other Atomic* types. 198 #if defined(GOOGLE_PROTOBUF_OS_APPLE) 199 #include <google/protobuf/stubs/atomicops_internals_atomicword_compat.h> 200 #endif 201 202 #undef GOOGLE_PROTOBUF_ATOMICOPS_ERROR 203 204 #endif // GOOGLE_PROTOBUF_NO_THREAD_SAFETY 205 206 #endif // GOOGLE_PROTOBUF_ATOMICOPS_H_ 207
