bbudge@chromium.org | 407d3b5 | 2012-08-23 03:22:03 +0900 | [diff] [blame] | 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, include base/atomicops.h |
| 6 | // instead. This file is for platforms that use GCC intrinsics rather than |
| 7 | // platform-specific assembly code for atomic operations. |
| 8 | |
| 9 | #ifndef BASE_ATOMICOPS_INTERNALS_GCC_H_ |
| 10 | #define BASE_ATOMICOPS_INTERNALS_GCC_H_ |
| 11 | |
| 12 | namespace base { |
| 13 | namespace subtle { |
| 14 | |
| 15 | inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr, |
| 16 | Atomic32 old_value, |
| 17 | Atomic32 new_value) { |
| 18 | Atomic32 prev_value; |
| 19 | do { |
bbudge@chromium.org | 9f4fa3a | 2012-08-23 06:55:24 +0900 | [diff] [blame] | 20 | if (__sync_bool_compare_and_swap(ptr, old_value, new_value)) |
| 21 | return old_value; |
| 22 | prev_value = *ptr; |
| 23 | } while (prev_value == old_value); |
| 24 | return prev_value; |
bbudge@chromium.org | 407d3b5 | 2012-08-23 03:22:03 +0900 | [diff] [blame] | 25 | } |
| 26 | |
| 27 | inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr, |
| 28 | Atomic32 new_value) { |
| 29 | Atomic32 old_value; |
| 30 | do { |
| 31 | old_value = *ptr; |
| 32 | } while (!__sync_bool_compare_and_swap(ptr, old_value, new_value)); |
| 33 | return old_value; |
| 34 | } |
| 35 | |
| 36 | inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, |
| 37 | Atomic32 increment) { |
| 38 | return Barrier_AtomicIncrement(ptr, increment); |
| 39 | } |
| 40 | |
| 41 | inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr, |
| 42 | Atomic32 increment) { |
| 43 | for (;;) { |
| 44 | // Atomic exchange the old value with an incremented one. |
| 45 | Atomic32 old_value = *ptr; |
| 46 | Atomic32 new_value = old_value + increment; |
| 47 | if (__sync_bool_compare_and_swap(ptr, old_value, new_value)) { |
| 48 | // The exchange took place as expected. |
| 49 | return new_value; |
| 50 | } |
| 51 | // Otherwise, *ptr changed mid-loop and we need to retry. |
| 52 | } |
| 53 | } |
| 54 | |
| 55 | inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr, |
| 56 | Atomic32 old_value, |
| 57 | Atomic32 new_value) { |
| 58 | // Since NoBarrier_CompareAndSwap uses __sync_bool_compare_and_swap, which |
| 59 | // is a full memory barrier, none is needed here or below in Release. |
| 60 | return NoBarrier_CompareAndSwap(ptr, old_value, new_value); |
| 61 | } |
| 62 | |
| 63 | inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr, |
| 64 | Atomic32 old_value, |
| 65 | Atomic32 new_value) { |
| 66 | return NoBarrier_CompareAndSwap(ptr, old_value, new_value); |
| 67 | } |
| 68 | |
| 69 | inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) { |
| 70 | *ptr = value; |
| 71 | } |
| 72 | |
| 73 | inline void MemoryBarrier() { |
| 74 | __sync_synchronize(); |
| 75 | } |
| 76 | |
| 77 | inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) { |
| 78 | *ptr = value; |
| 79 | MemoryBarrier(); |
| 80 | } |
| 81 | |
| 82 | inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) { |
| 83 | MemoryBarrier(); |
| 84 | *ptr = value; |
| 85 | } |
| 86 | |
| 87 | inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) { |
| 88 | return *ptr; |
| 89 | } |
| 90 | |
| 91 | inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) { |
| 92 | Atomic32 value = *ptr; |
| 93 | MemoryBarrier(); |
| 94 | return value; |
| 95 | } |
| 96 | |
| 97 | inline Atomic32 Release_Load(volatile const Atomic32* ptr) { |
| 98 | MemoryBarrier(); |
| 99 | return *ptr; |
| 100 | } |
| 101 | |
| 102 | } // namespace base::subtle |
| 103 | } // namespace base |
| 104 | |
| 105 | #endif // BASE_ATOMICOPS_INTERNALS_GCC_H_ |
| 106 | |