1 // Copyright 2010 The Chromium Authors
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/threading/thread_collision_warner.h"
6
7 #include <ostream>
8
9 #include "base/notreached.h"
10 #include "base/threading/platform_thread.h"
11
12 namespace base {
13
warn()14 void DCheckAsserter::warn() {
15 NOTREACHED() << "Thread Collision";
16 }
17
CurrentThread()18 static subtle::Atomic32 CurrentThread() {
19 const PlatformThreadId current_thread_id = PlatformThread::CurrentId();
20 // We need to get the thread id into an atomic data type. This might be a
21 // truncating conversion, but any loss-of-information just increases the
22 // chance of a fault negative, not a false positive.
23 const subtle::Atomic32 atomic_thread_id =
24 static_cast<subtle::Atomic32>(current_thread_id);
25
26 return atomic_thread_id;
27 }
28
EnterSelf()29 void ThreadCollisionWarner::EnterSelf() {
30 // If the active thread is 0 then I'll write the current thread ID
31 // if two or more threads arrive here only one will succeed to
32 // write on valid_thread_id_ the current thread ID.
33 subtle::Atomic32 current_thread_id = CurrentThread();
34
35 int previous_value = subtle::NoBarrier_CompareAndSwap(&valid_thread_id_,
36 0,
37 current_thread_id);
38 if (previous_value != 0 && previous_value != current_thread_id) {
39 // gotcha! a thread is trying to use the same class and that is
40 // not current thread.
41 asserter_->warn();
42 }
43
44 subtle::NoBarrier_AtomicIncrement(&counter_, 1);
45 }
46
Enter()47 void ThreadCollisionWarner::Enter() {
48 subtle::Atomic32 current_thread_id = CurrentThread();
49
50 if (subtle::NoBarrier_CompareAndSwap(&valid_thread_id_,
51 0,
52 current_thread_id) != 0) {
53 // gotcha! another thread is trying to use the same class.
54 asserter_->warn();
55 }
56
57 subtle::NoBarrier_AtomicIncrement(&counter_, 1);
58 }
59
Leave()60 void ThreadCollisionWarner::Leave() {
61 if (subtle::Barrier_AtomicIncrement(&counter_, -1) == 0) {
62 subtle::NoBarrier_Store(&valid_thread_id_, 0);
63 }
64 }
65
66 } // namespace base
67