1// Copyright 2010 the V8 project authors. All rights reserved. 2// Redistribution and use in source and binary forms, with or without 3// modification, are permitted provided that the following conditions are 4// met: 5// 6// * Redistributions of source code must retain the above copyright 7// notice, this list of conditions and the following disclaimer. 8// * Redistributions in binary form must reproduce the above 9// copyright notice, this list of conditions and the following 10// disclaimer in the documentation and/or other materials provided 11// with the distribution. 12// * Neither the name of Google Inc. nor the names of its 13// contributors may be used to endorse or promote products derived 14// from this software without specific prior written permission. 15// 16// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 28// This file is an internal atomic implementation, use atomicops.h instead. 29// 30// LinuxKernelCmpxchg and Barrier_AtomicIncrement are from Google Gears. 31 32#ifndef V8_ATOMICOPS_INTERNALS_ARM_GCC_H_ 33#define V8_ATOMICOPS_INTERNALS_ARM_GCC_H_ 34 35namespace v8 { 36namespace internal { 37 38// 0xffff0fc0 is the hard coded address of a function provided by 39// the kernel which implements an atomic compare-exchange. On older 40// ARM architecture revisions (pre-v6) this may be implemented using 41// a syscall. This address is stable, and in active use (hard coded) 42// by at least glibc-2.7 and the Android C library. 43typedef Atomic32 (*LinuxKernelCmpxchgFunc)(Atomic32 old_value, 44 Atomic32 new_value, 45 volatile Atomic32* ptr); 46LinuxKernelCmpxchgFunc pLinuxKernelCmpxchg __attribute__((weak)) = 47 (LinuxKernelCmpxchgFunc) 0xffff0fc0; 48 49typedef void (*LinuxKernelMemoryBarrierFunc)(void); 50LinuxKernelMemoryBarrierFunc pLinuxKernelMemoryBarrier __attribute__((weak)) = 51 (LinuxKernelMemoryBarrierFunc) 0xffff0fa0; 52 53 54inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr, 55 Atomic32 old_value, 56 Atomic32 new_value) { 57 Atomic32 prev_value = *ptr; 58 do { 59 if (!pLinuxKernelCmpxchg(old_value, new_value, 60 const_cast<Atomic32*>(ptr))) { 61 return old_value; 62 } 63 prev_value = *ptr; 64 } while (prev_value == old_value); 65 return prev_value; 66} 67 68inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr, 69 Atomic32 new_value) { 70 Atomic32 old_value; 71 do { 72 old_value = *ptr; 73 } while (pLinuxKernelCmpxchg(old_value, new_value, 74 const_cast<Atomic32*>(ptr))); 75 return old_value; 76} 77 78inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, 79 Atomic32 increment) { 80 return Barrier_AtomicIncrement(ptr, increment); 81} 82 83inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr, 84 Atomic32 increment) { 85 for (;;) { 86 // Atomic exchange the old value with an incremented one. 87 Atomic32 old_value = *ptr; 88 Atomic32 new_value = old_value + increment; 89 if (pLinuxKernelCmpxchg(old_value, new_value, 90 const_cast<Atomic32*>(ptr)) == 0) { 91 // The exchange took place as expected. 92 return new_value; 93 } 94 // Otherwise, *ptr changed mid-loop and we need to retry. 95 } 96} 97 98inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr, 99 Atomic32 old_value, 100 Atomic32 new_value) { 101 return NoBarrier_CompareAndSwap(ptr, old_value, new_value); 102} 103 104inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr, 105 Atomic32 old_value, 106 Atomic32 new_value) { 107 return NoBarrier_CompareAndSwap(ptr, old_value, new_value); 108} 109 110inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) { 111 *ptr = value; 112} 113 114inline void MemoryBarrier() { 115 pLinuxKernelMemoryBarrier(); 116} 117 118inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) { 119 *ptr = value; 120 MemoryBarrier(); 121} 122 123inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) { 124 MemoryBarrier(); 125 *ptr = value; 126} 127 128inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) { 129 return *ptr; 130} 131 132inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) { 133 Atomic32 value = *ptr; 134 MemoryBarrier(); 135 return value; 136} 137 138inline Atomic32 Release_Load(volatile const Atomic32* ptr) { 139 MemoryBarrier(); 140 return *ptr; 141} 142 143} } // namespace v8::internal 144 145#endif // V8_ATOMICOPS_INTERNALS_ARM_GCC_H_ 146