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comparison: ipc/chromium/src/base/atomicops_internals_arm_gcc.h
ipc/chromium/src/base/atomicops_internals_arm_gcc.h
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| -1:000000000000 | 0:2947a8e44a26 |
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| 1 // Copyright (c) 2009 The Chromium 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 // This file is an internal atomic implementation, use base/atomicops.h instead. | |
| 6 // | |
| 7 // LinuxKernelCmpxchg and Barrier_AtomicIncrement are from Google Gears. | |
| 8 | |
| 9 #ifndef BASE_ATOMICOPS_INTERNALS_ARM_GCC_H_ | |
| 10 #define BASE_ATOMICOPS_INTERNALS_ARM_GCC_H_ | |
| 11 | |
| 12 namespace base { | |
| 13 namespace subtle { | |
| 14 | |
| 15 // 0xffff0fc0 is the hard coded address of a function provided by | |
| 16 // the kernel which implements an atomic compare-exchange. On older | |
| 17 // ARM architecture revisions (pre-v6) this may be implemented using | |
| 18 // a syscall. This address is stable, and in active use (hard coded) | |
| 19 // by at least glibc-2.7 and the Android C library. | |
| 20 typedef Atomic32 (*LinuxKernelCmpxchgFunc)(Atomic32 old_value, | |
| 21 Atomic32 new_value, | |
| 22 volatile Atomic32* ptr); | |
| 23 LinuxKernelCmpxchgFunc pLinuxKernelCmpxchg __attribute__((weak)) = | |
| 24 (LinuxKernelCmpxchgFunc) 0xffff0fc0; | |
| 25 | |
| 26 typedef void (*LinuxKernelMemoryBarrierFunc)(void); | |
| 27 LinuxKernelMemoryBarrierFunc pLinuxKernelMemoryBarrier __attribute__((weak)) = | |
| 28 (LinuxKernelMemoryBarrierFunc) 0xffff0fa0; | |
| 29 | |
| 30 | |
| 31 inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr, | |
| 32 Atomic32 old_value, | |
| 33 Atomic32 new_value) { | |
| 34 Atomic32 prev_value = *ptr; | |
| 35 do { | |
| 36 if (!pLinuxKernelCmpxchg(old_value, new_value, | |
| 37 const_cast<Atomic32*>(ptr))) { | |
| 38 return old_value; | |
| 39 } | |
| 40 prev_value = *ptr; | |
| 41 } while (prev_value == old_value); | |
| 42 return prev_value; | |
| 43 } | |
| 44 | |
| 45 inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr, | |
| 46 Atomic32 new_value) { | |
| 47 Atomic32 old_value; | |
| 48 do { | |
| 49 old_value = *ptr; | |
| 50 } while (pLinuxKernelCmpxchg(old_value, new_value, | |
| 51 const_cast<Atomic32*>(ptr))); | |
| 52 return old_value; | |
| 53 } | |
| 54 | |
| 55 inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, | |
| 56 Atomic32 increment) { | |
| 57 return Barrier_AtomicIncrement(ptr, increment); | |
| 58 } | |
| 59 | |
| 60 inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr, | |
| 61 Atomic32 increment) { | |
| 62 for (;;) { | |
| 63 // Atomic exchange the old value with an incremented one. | |
| 64 Atomic32 old_value = *ptr; | |
| 65 Atomic32 new_value = old_value + increment; | |
| 66 if (pLinuxKernelCmpxchg(old_value, new_value, | |
| 67 const_cast<Atomic32*>(ptr)) == 0) { | |
| 68 // The exchange took place as expected. | |
| 69 return new_value; | |
| 70 } | |
| 71 // Otherwise, *ptr changed mid-loop and we need to retry. | |
| 72 } | |
| 73 | |
| 74 } | |
| 75 | |
| 76 inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr, | |
| 77 Atomic32 old_value, | |
| 78 Atomic32 new_value) { | |
| 79 return NoBarrier_CompareAndSwap(ptr, old_value, new_value); | |
| 80 } | |
| 81 | |
| 82 inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr, | |
| 83 Atomic32 old_value, | |
| 84 Atomic32 new_value) { | |
| 85 return NoBarrier_CompareAndSwap(ptr, old_value, new_value); | |
| 86 } | |
| 87 | |
| 88 inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) { | |
| 89 *ptr = value; | |
| 90 } | |
| 91 | |
| 92 inline void MemoryBarrier() { | |
| 93 pLinuxKernelMemoryBarrier(); | |
| 94 } | |
| 95 | |
| 96 inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) { | |
| 97 *ptr = value; | |
| 98 MemoryBarrier(); | |
| 99 } | |
| 100 | |
| 101 inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) { | |
| 102 MemoryBarrier(); | |
| 103 *ptr = value; | |
| 104 } | |
| 105 | |
| 106 inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) { | |
| 107 return *ptr; | |
| 108 } | |
| 109 | |
| 110 inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) { | |
| 111 Atomic32 value = *ptr; | |
| 112 MemoryBarrier(); | |
| 113 return value; | |
| 114 } | |
| 115 | |
| 116 inline Atomic32 Release_Load(volatile const Atomic32* ptr) { | |
| 117 MemoryBarrier(); | |
| 118 return *ptr; | |
| 119 } | |
| 120 | |
| 121 } // namespace base::subtle | |
| 122 } // namespace base | |
| 123 | |
| 124 #endif // BASE_ATOMICOPS_INTERNALS_ARM_GCC_H_ |
