thread.cc revision 9306e92a0b28f7c70a3e29272141b0e271452479 
1// Copyright (c) 2006-2009 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/threading/thread.h"
6
7#include "base/lazy_instance.h"
8#include "base/third_party/dynamic_annotations/dynamic_annotations.h"
9#include "base/threading/thread_local.h"
10#include "base/synchronization/waitable_event.h"
11
12namespace base {
13
14namespace {
15
16// We use this thread-local variable to record whether or not a thread exited
17// because its Stop method was called.  This allows us to catch cases where
18// MessageLoop::Quit() is called directly, which is unexpected when using a
19// Thread to setup and run a MessageLoop.
20base::LazyInstance<base::ThreadLocalBoolean> lazy_tls_bool(
21    base::LINKER_INITIALIZED);
22
23}  // namespace
24
25// This task is used to trigger the message loop to exit.
26class ThreadQuitTask : public Task {
27 public:
28  virtual void Run() {
29    MessageLoop::current()->Quit();
30    Thread::SetThreadWasQuitProperly(true);
31  }
32};
33
34// Used to pass data to ThreadMain.  This structure is allocated on the stack
35// from within StartWithOptions.
36struct Thread::StartupData {
37  // We get away with a const reference here because of how we are allocated.
38  const Thread::Options& options;
39
40  // Used to synchronize thread startup.
41  WaitableEvent event;
42
43  explicit StartupData(const Options& opt)
44      : options(opt),
45        event(false, false) {}
46};
47
48Thread::Thread(const char* name)
49    : started_(false),
50      stopping_(false),
51      startup_data_(NULL),
52      thread_(0),
53      message_loop_(NULL),
54      thread_id_(kInvalidThreadId),
55      name_(name) {
56}
57
58Thread::~Thread() {
59  Stop();
60}
61
62bool Thread::Start() {
63  return StartWithOptions(Options());
64}
65
66bool Thread::StartWithOptions(const Options& options) {
67  DCHECK(!message_loop_);
68
69  SetThreadWasQuitProperly(false);
70
71  StartupData startup_data(options);
72  startup_data_ = &startup_data;
73
74  if (!PlatformThread::Create(options.stack_size, this, &thread_)) {
75    DLOG(ERROR) << "failed to create thread";
76#if defined(ANDROID)
77    // For debugging. See http://b/5244039
78    startup_data_ = reinterpret_cast<StartupData*>(0xdeadd00d);
79#else
80    startup_data_ = NULL;
81#endif
82    return false;
83  }
84
85  // Wait for the thread to start and initialize message_loop_
86  startup_data.event.Wait();
87
88  // set it to NULL so we don't keep a pointer to some object on the stack.
89#if defined(ANDROID)
90  // For debugging. See http://b/5244039
91  startup_data_ = reinterpret_cast<StartupData*>(0xbbadbeef);
92#else
93  startup_data_ = NULL;
94#endif
95  started_ = true;
96
97  DCHECK(message_loop_);
98  return true;
99}
100
101void Thread::Stop() {
102  if (!thread_was_started())
103    return;
104
105  StopSoon();
106
107  // Wait for the thread to exit.
108  //
109  // TODO(darin): Unfortunately, we need to keep message_loop_ around until
110  // the thread exits.  Some consumers are abusing the API.  Make them stop.
111  //
112  PlatformThread::Join(thread_);
113
114  // The thread should NULL message_loop_ on exit.
115  DCHECK(!message_loop_);
116
117  // The thread no longer needs to be joined.
118  started_ = false;
119
120  stopping_ = false;
121}
122
123void Thread::StopSoon() {
124  // We should only be called on the same thread that started us.
125
126  // Reading thread_id_ without a lock can lead to a benign data race
127  // with ThreadMain, so we annotate it to stay silent under ThreadSanitizer.
128  DCHECK_NE(ANNOTATE_UNPROTECTED_READ(thread_id_), PlatformThread::CurrentId());
129
130  if (stopping_ || !message_loop_)
131    return;
132
133  stopping_ = true;
134  message_loop_->PostTask(FROM_HERE, new ThreadQuitTask());
135}
136
137void Thread::Run(MessageLoop* message_loop) {
138  message_loop->Run();
139}
140
141void Thread::SetThreadWasQuitProperly(bool flag) {
142  lazy_tls_bool.Pointer()->Set(flag);
143}
144
145bool Thread::GetThreadWasQuitProperly() {
146  bool quit_properly = true;
147#ifndef NDEBUG
148  quit_properly = lazy_tls_bool.Pointer()->Get();
149#endif
150  return quit_properly;
151}
152
153void Thread::ThreadMain() {
154  {
155    // The message loop for this thread.
156    MessageLoop message_loop(startup_data_->options.message_loop_type);
157
158    // Complete the initialization of our Thread object.
159    thread_id_ = PlatformThread::CurrentId();
160    PlatformThread::SetName(name_.c_str());
161    ANNOTATE_THREAD_NAME(name_.c_str());  // Tell the name to race detector.
162    message_loop.set_thread_name(name_);
163    message_loop_ = &message_loop;
164    message_loop_proxy_ = MessageLoopProxy::CreateForCurrentThread();
165
166    // Let the thread do extra initialization.
167    // Let's do this before signaling we are started.
168    Init();
169
170    startup_data_->event.Signal();
171    // startup_data_ can't be touched anymore since the starting thread is now
172    // unlocked.
173
174    Run(message_loop_);
175
176    // Let the thread do extra cleanup.
177    CleanUp();
178
179    // Assert that MessageLoop::Quit was called by ThreadQuitTask.
180    DCHECK(GetThreadWasQuitProperly());
181
182    // We can't receive messages anymore.
183    message_loop_ = NULL;
184    message_loop_proxy_ = NULL;
185  }
186  thread_id_ = kInvalidThreadId;
187}
188
189}  // namespace base
190