1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/security/sandbox/chromium/base/memory/singleton.cc Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,31 @@
1.4 +// Copyright (c) 2011 The Chromium Authors. All rights reserved.
1.5 +// Use of this source code is governed by a BSD-style license that can be
1.6 +// found in the LICENSE file.
1.7 +
1.8 +#include "base/memory/singleton.h"
1.9 +#include "base/threading/platform_thread.h"
1.10 +
1.11 +namespace base {
1.12 +namespace internal {
1.13 +
1.14 +subtle::AtomicWord WaitForInstance(subtle::AtomicWord* instance) {
1.15 + // Handle the race. Another thread beat us and either:
1.16 + // - Has the object in BeingCreated state
1.17 + // - Already has the object created...
1.18 + // We know value != NULL. It could be kBeingCreatedMarker, or a valid ptr.
1.19 + // Unless your constructor can be very time consuming, it is very unlikely
1.20 + // to hit this race. When it does, we just spin and yield the thread until
1.21 + // the object has been created.
1.22 + subtle::AtomicWord value;
1.23 + while (true) {
1.24 + value = subtle::NoBarrier_Load(instance);
1.25 + if (value != kBeingCreatedMarker)
1.26 + break;
1.27 + PlatformThread::YieldCurrentThread();
1.28 + }
1.29 + return value;
1.30 +}
1.31 +
1.32 +} // namespace internal
1.33 +} // namespace base
1.34 +
