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44 lines
1.5 KiB
44 lines
1.5 KiB
// Copyright (c) 2010 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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#include "base/lazy_instance.h"
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#include "base/at_exit.h"
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#include "base/atomicops.h"
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#include "base/basictypes.h"
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#include "base/threading/platform_thread.h"
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#include "base/third_party/dynamic_annotations/dynamic_annotations.h"
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namespace base {
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bool LazyInstanceHelper::NeedsInstance() {
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// Try to create the instance, if we're the first, will go from EMPTY
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// to CREATING, otherwise we've already been beaten here.
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if (base::subtle::Acquire_CompareAndSwap(
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&state_, STATE_EMPTY, STATE_CREATING) == STATE_EMPTY) {
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// Caller must create instance
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return true;
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} else {
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// It's either in the process of being created, or already created. Spin.
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while (base::subtle::NoBarrier_Load(&state_) != STATE_CREATED)
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PlatformThread::YieldCurrentThread();
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}
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// Someone else created the instance.
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return false;
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}
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void LazyInstanceHelper::CompleteInstance(void* instance, void (*dtor)(void*)) {
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// See the comment to the corresponding HAPPENS_AFTER in Pointer().
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ANNOTATE_HAPPENS_BEFORE(&state_);
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// Instance is created, go from CREATING to CREATED.
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base::subtle::Release_Store(&state_, STATE_CREATED);
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// Make sure that the lazily instantiated object will get destroyed at exit.
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if (dtor)
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base::AtExitManager::RegisterCallback(dtor, instance);
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}
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} // namespace base
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