security/sandbox/chromium/base/memory/singleton.cc@44a2da4a2ab2 (annotated)
security/sandbox/chromium/base/memory/singleton.cc
Fri, 16 Jan 2015 04:50:19 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Fri, 16 Jan 2015 04:50:19 +0100
- branch
- TOR_BUG_9701
- changeset 13
- 44a2da4a2ab2
- permissions
- -rw-r--r--
Replace accessor implementation with direct member state manipulation, by
request https://trac.torproject.org/projects/tor/ticket/9701#comment:32
| michael@0 | 1 | // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
| michael@0 | 2 | // Use of this source code is governed by a BSD-style license that can be |
| michael@0 | 3 | // found in the LICENSE file. |
| michael@0 | 4 | |
| michael@0 | 5 | #include "base/memory/singleton.h" |
| michael@0 | 6 | #include "base/threading/platform_thread.h" |
| michael@0 | 7 | |
| michael@0 | 8 | namespace base { |
| michael@0 | 9 | namespace internal { |
| michael@0 | 10 | |
| michael@0 | 11 | subtle::AtomicWord WaitForInstance(subtle::AtomicWord* instance) { |
| michael@0 | 12 | // Handle the race. Another thread beat us and either: |
| michael@0 | 13 | // - Has the object in BeingCreated state |
| michael@0 | 14 | // - Already has the object created... |
| michael@0 | 15 | // We know value != NULL. It could be kBeingCreatedMarker, or a valid ptr. |
| michael@0 | 16 | // Unless your constructor can be very time consuming, it is very unlikely |
| michael@0 | 17 | // to hit this race. When it does, we just spin and yield the thread until |
| michael@0 | 18 | // the object has been created. |
| michael@0 | 19 | subtle::AtomicWord value; |
| michael@0 | 20 | while (true) { |
| michael@0 | 21 | value = subtle::NoBarrier_Load(instance); |
| michael@0 | 22 | if (value != kBeingCreatedMarker) |
| michael@0 | 23 | break; |
| michael@0 | 24 | PlatformThread::YieldCurrentThread(); |
| michael@0 | 25 | } |
| michael@0 | 26 | return value; |
| michael@0 | 27 | } |
| michael@0 | 28 | |
| michael@0 | 29 | } // namespace internal |
| michael@0 | 30 | } // namespace base |
| michael@0 | 31 |
