1 : // Copyright (c) 2006-2008 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/thread_collision_warner.h"
6 :
7 : #include "base/logging.h"
8 : #include "base/platform_thread.h"
9 :
10 : namespace base {
11 :
12 0 : void DCheckAsserter::warn() {
13 0 : NOTREACHED() << "Thread Collision";
14 0 : }
15 :
16 0 : static subtle::Atomic32 CurrentThread() {
17 0 : const PlatformThreadId current_thread_id = PlatformThread::CurrentId();
18 : // We need to get the thread id into an atomic data type. This might be a
19 : // truncating conversion, but any loss-of-information just increases the
20 : // chance of a fault negative, not a false positive.
21 : const subtle::Atomic32 atomic_thread_id =
22 0 : static_cast<subtle::Atomic32>(current_thread_id);
23 :
24 0 : return atomic_thread_id;
25 : }
26 :
27 0 : void ThreadCollisionWarner::EnterSelf() {
28 : // If the active thread is 0 then I'll write the current thread ID
29 : // if two or more threads arrive here only one will succeed to
30 : // write on valid_thread_id_ the current thread ID.
31 0 : subtle::Atomic32 current_thread_id = CurrentThread();
32 :
33 : int previous_value = subtle::NoBarrier_CompareAndSwap(&valid_thread_id_,
34 : 0,
35 0 : current_thread_id);
36 0 : if (previous_value != 0 && previous_value != current_thread_id) {
37 : // gotcha! a thread is trying to use the same class and that is
38 : // not current thread.
39 0 : asserter_->warn();
40 : }
41 :
42 0 : subtle::NoBarrier_AtomicIncrement(&counter_, 1);
43 0 : }
44 :
45 0 : void ThreadCollisionWarner::Enter() {
46 0 : subtle::Atomic32 current_thread_id = CurrentThread();
47 :
48 0 : if (subtle::NoBarrier_CompareAndSwap(&valid_thread_id_,
49 : 0,
50 0 : current_thread_id) != 0) {
51 : // gotcha! another thread is trying to use the same class.
52 0 : asserter_->warn();
53 : }
54 :
55 0 : subtle::NoBarrier_AtomicIncrement(&counter_, 1);
56 0 : }
57 :
58 0 : void ThreadCollisionWarner::Leave() {
59 0 : if (subtle::Barrier_AtomicIncrement(&counter_, -1) == 0) {
60 0 : subtle::NoBarrier_Store(&valid_thread_id_, 0);
61 : }
62 0 : }
63 :
64 : } // namespace base
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