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comparison: security/sandbox/chromium/base/memory/singleton.cc
security/sandbox/chromium/base/memory/singleton.cc
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| 1 // Copyright (c) 2011 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 #include "base/memory/singleton.h" | |
| 6 #include "base/threading/platform_thread.h" | |
| 7 | |
| 8 namespace base { | |
| 9 namespace internal { | |
| 10 | |
| 11 subtle::AtomicWord WaitForInstance(subtle::AtomicWord* instance) { | |
| 12 // Handle the race. Another thread beat us and either: | |
| 13 // - Has the object in BeingCreated state | |
| 14 // - Already has the object created... | |
| 15 // We know value != NULL. It could be kBeingCreatedMarker, or a valid ptr. | |
| 16 // Unless your constructor can be very time consuming, it is very unlikely | |
| 17 // to hit this race. When it does, we just spin and yield the thread until | |
| 18 // the object has been created. | |
| 19 subtle::AtomicWord value; | |
| 20 while (true) { | |
| 21 value = subtle::NoBarrier_Load(instance); | |
| 22 if (value != kBeingCreatedMarker) | |
| 23 break; | |
| 24 PlatformThread::YieldCurrentThread(); | |
| 25 } | |
| 26 return value; | |
| 27 } | |
| 28 | |
| 29 } // namespace internal | |
| 30 } // namespace base | |
| 31 |
