107 lines
3.2 KiB
C
107 lines
3.2 KiB
C
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// Copyright (c) 2009 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// This file is an internal atomic implementation, include base/atomicops.h
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// instead. This file is for platforms that use GCC intrinsics rather than
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// platform-specific assembly code for atomic operations.
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#ifndef BASE_ATOMICOPS_INTERNALS_GCC_H_
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#define BASE_ATOMICOPS_INTERNALS_GCC_H_
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namespace base {
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namespace subtle {
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inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
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Atomic32 old_value,
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Atomic32 new_value) {
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Atomic32 prev_value;
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do {
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if (__sync_bool_compare_and_swap(ptr, old_value, new_value))
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return old_value;
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prev_value = *ptr;
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} while (prev_value == old_value);
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return prev_value;
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}
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inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
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Atomic32 new_value) {
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Atomic32 old_value;
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do {
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old_value = *ptr;
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} while (!__sync_bool_compare_and_swap(ptr, old_value, new_value));
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return old_value;
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}
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inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
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Atomic32 increment) {
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return Barrier_AtomicIncrement(ptr, increment);
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}
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inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
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Atomic32 increment) {
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for (;;) {
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// Atomic exchange the old value with an incremented one.
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Atomic32 old_value = *ptr;
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Atomic32 new_value = old_value + increment;
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if (__sync_bool_compare_and_swap(ptr, old_value, new_value)) {
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// The exchange took place as expected.
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return new_value;
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}
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// Otherwise, *ptr changed mid-loop and we need to retry.
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}
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}
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inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
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Atomic32 old_value,
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Atomic32 new_value) {
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// Since NoBarrier_CompareAndSwap uses __sync_bool_compare_and_swap, which
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// is a full memory barrier, none is needed here or below in Release.
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return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
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}
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inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
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Atomic32 old_value,
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Atomic32 new_value) {
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return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
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}
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inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
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*ptr = value;
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}
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inline void MemoryBarrier() {
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__sync_synchronize();
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}
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inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
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*ptr = value;
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MemoryBarrier();
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}
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inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
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MemoryBarrier();
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*ptr = value;
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}
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inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
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return *ptr;
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}
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inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
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Atomic32 value = *ptr;
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MemoryBarrier();
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return value;
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}
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inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
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MemoryBarrier();
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return *ptr;
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}
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} // namespace base::subtle
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} // namespace base
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#endif // BASE_ATOMICOPS_INTERNALS_GCC_H_
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