summaryrefslogtreecommitdiff
path: root/base/threading/thread.cc
blob: 616aac8933a5a1a3b75c7a0588f07f92aeda5b03 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/threading/thread.h"

#include "base/lazy_instance.h"
#include "base/third_party/dynamic_annotations/dynamic_annotations.h"
#include "base/threading/thread_local.h"
#include "base/synchronization/waitable_event.h"

namespace base {

namespace {

// We use this thread-local variable to record whether or not a thread exited
// because its Stop method was called.  This allows us to catch cases where
// MessageLoop::Quit() is called directly, which is unexpected when using a
// Thread to setup and run a MessageLoop.
base::LazyInstance<base::ThreadLocalBoolean> lazy_tls_bool(
    base::LINKER_INITIALIZED);

}  // namespace

// This task is used to trigger the message loop to exit.
class ThreadQuitTask : public Task {
 public:
  virtual void Run() {
    MessageLoop::current()->Quit();
    Thread::SetThreadWasQuitProperly(true);
  }
};

// Used to pass data to ThreadMain.  This structure is allocated on the stack
// from within StartWithOptions.
struct Thread::StartupData {
  // We get away with a const reference here because of how we are allocated.
  const Thread::Options& options;

  // Used to synchronize thread startup.
  WaitableEvent event;

  explicit StartupData(const Options& opt)
      : options(opt),
        event(false, false) {}
};

Thread::Thread(const char* name)
    : started_(false),
      stopping_(false),
      startup_data_(NULL),
      thread_(0),
      message_loop_(NULL),
      thread_id_(kInvalidThreadId),
      name_(name) {
}

Thread::~Thread() {
  Stop();
}

bool Thread::Start() {
  return StartWithOptions(Options());
}

bool Thread::StartWithOptions(const Options& options) {
  DCHECK(!message_loop_);

  SetThreadWasQuitProperly(false);

  StartupData startup_data(options);
  startup_data_ = &startup_data;

  if (!PlatformThread::Create(options.stack_size, this, &thread_)) {
    DLOG(ERROR) << "failed to create thread";
    startup_data_ = NULL;
    return false;
  }

  // Wait for the thread to start and initialize message_loop_
  startup_data.event.Wait();

  // set it to NULL so we don't keep a pointer to some object on the stack.
  startup_data_ = NULL;
  started_ = true;

  DCHECK(message_loop_);
  return true;
}

void Thread::Stop() {
  if (!thread_was_started())
    return;

  StopSoon();

  // Wait for the thread to exit.
  //
  // TODO(darin): Unfortunately, we need to keep message_loop_ around until
  // the thread exits.  Some consumers are abusing the API.  Make them stop.
  //
  PlatformThread::Join(thread_);

  // The thread should NULL message_loop_ on exit.
  DCHECK(!message_loop_);

  // The thread no longer needs to be joined.
  started_ = false;

  stopping_ = false;
}

void Thread::StopSoon() {
  // We should only be called on the same thread that started us.

  // Reading thread_id_ without a lock can lead to a benign data race
  // with ThreadMain, so we annotate it to stay silent under ThreadSanitizer.
  DCHECK_NE(ANNOTATE_UNPROTECTED_READ(thread_id_), PlatformThread::CurrentId());

  if (stopping_ || !message_loop_)
    return;

  stopping_ = true;
  message_loop_->PostTask(FROM_HERE, new ThreadQuitTask());
}

void Thread::Run(MessageLoop* message_loop) {
  message_loop->Run();
}

void Thread::SetThreadWasQuitProperly(bool flag) {
  lazy_tls_bool.Pointer()->Set(flag);
}

bool Thread::GetThreadWasQuitProperly() {
  bool quit_properly = true;
#ifndef NDEBUG
  quit_properly = lazy_tls_bool.Pointer()->Get();
#endif
  return quit_properly;
}

void Thread::ThreadMain() {
  {
    // The message loop for this thread.
    MessageLoop message_loop(startup_data_->options.message_loop_type);

    // Complete the initialization of our Thread object.
    thread_id_ = PlatformThread::CurrentId();
    PlatformThread::SetName(name_.c_str());
    ANNOTATE_THREAD_NAME(name_.c_str());  // Tell the name to race detector.
    message_loop.set_thread_name(name_);
    message_loop_ = &message_loop;

    // Let the thread do extra initialization.
    // Let's do this before signaling we are started.
    Init();

    startup_data_->event.Signal();
    // startup_data_ can't be touched anymore since the starting thread is now
    // unlocked.

    Run(message_loop_);

    // Let the thread do extra cleanup.
    CleanUp();

    // Assert that MessageLoop::Quit was called by ThreadQuitTask.
    DCHECK(GetThreadWasQuitProperly());

    // We can't receive messages anymore.
    message_loop_ = NULL;
  }
  thread_id_ = kInvalidThreadId;
}

}  // namespace base