thread.cc revision 72a454cd3513ac24fbdd0e0cb9ad70b86a99b801 
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    startup_data_ = NULL;
77    return false;
78  }
79
80  // Wait for the thread to start and initialize message_loop_
81  startup_data.event.Wait();
82
83  // set it to NULL so we don't keep a pointer to some object on the stack.
84  startup_data_ = NULL;
85  started_ = true;
86
87  DCHECK(message_loop_);
88  return true;
89}
90
91void Thread::Stop() {
92  if (!thread_was_started())
93    return;
94
95  StopSoon();
96
97  // Wait for the thread to exit.
98  //
99  // TODO(darin): Unfortunately, we need to keep message_loop_ around until
100  // the thread exits.  Some consumers are abusing the API.  Make them stop.
101  //
102  PlatformThread::Join(thread_);
103
104  // The thread should NULL message_loop_ on exit.
105  DCHECK(!message_loop_);
106
107  // The thread no longer needs to be joined.
108  started_ = false;
109
110  stopping_ = false;
111}
112
113void Thread::StopSoon() {
114  // We should only be called on the same thread that started us.
115
116  // Reading thread_id_ without a lock can lead to a benign data race
117  // with ThreadMain, so we annotate it to stay silent under ThreadSanitizer.
118  DCHECK_NE(ANNOTATE_UNPROTECTED_READ(thread_id_), PlatformThread::CurrentId());
119
120  if (stopping_ || !message_loop_)
121    return;
122
123  stopping_ = true;
124  message_loop_->PostTask(FROM_HERE, new ThreadQuitTask());
125}
126
127void Thread::Run(MessageLoop* message_loop) {
128  message_loop->Run();
129}
130
131void Thread::SetThreadWasQuitProperly(bool flag) {
132  lazy_tls_bool.Pointer()->Set(flag);
133}
134
135bool Thread::GetThreadWasQuitProperly() {
136  bool quit_properly = true;
137#ifndef NDEBUG
138  quit_properly = lazy_tls_bool.Pointer()->Get();
139#endif
140  return quit_properly;
141}
142
143void Thread::ThreadMain() {
144  {
145    // The message loop for this thread.
146    MessageLoop message_loop(startup_data_->options.message_loop_type);
147
148    // Complete the initialization of our Thread object.
149    thread_id_ = PlatformThread::CurrentId();
150    PlatformThread::SetName(name_.c_str());
151    ANNOTATE_THREAD_NAME(name_.c_str());  // Tell the name to race detector.
152    message_loop.set_thread_name(name_);
153    message_loop_ = &message_loop;
154    message_loop_proxy_ = MessageLoopProxy::CreateForCurrentThread();
155
156    // Let the thread do extra initialization.
157    // Let's do this before signaling we are started.
158    Init();
159
160    startup_data_->event.Signal();
161    // startup_data_ can't be touched anymore since the starting thread is now
162    // unlocked.
163
164    Run(message_loop_);
165
166    // Let the thread do extra cleanup.
167    CleanUp();
168
169    // Assert that MessageLoop::Quit was called by ThreadQuitTask.
170    DCHECK(GetThreadWasQuitProperly());
171
172    // We can't receive messages anymore.
173    message_loop_ = NULL;
174    message_loop_proxy_ = NULL;
175  }
176  CleanUpAfterMessageLoopDestruction();
177  thread_id_ = kInvalidThreadId;
178}
179
180}  // namespace base
181