base/threading/thread.cc

   1 // Copyright (c) 2012 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/bind.h"
   8 #include "base/lazy_instance.h"
   9 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
  10 #include "base/threading/thread_local.h"
  11 #include "base/threading/thread_restrictions.h"
  12 #include "base/synchronization/waitable_event.h"
  13
  14 #if defined(OS_WIN)
  15 #include "base/win/scoped_com_initializer.h"
  16 #endif
  17
  18 namespace base {
  19
  20 namespace {
  21
  22 // We use this thread-local variable to record whether or not a thread exited
  23 // because its Stop method was called.  This allows us to catch cases where
  24 // MessageLoop::Quit() is called directly, which is unexpected when using a
  25 // Thread to setup and run a MessageLoop.
  26 base::LazyInstance<base::ThreadLocalBoolean> lazy_tls_bool =
  27     LAZY_INSTANCE_INITIALIZER;
  28
  29 }  // namespace
  30
  31 // This is used to trigger the message loop to exit.
  32 void ThreadQuitHelper() {
  33   MessageLoop::current()->Quit();
  34   Thread::SetThreadWasQuitProperly(true);
  35 }
  36
  37 // Used to pass data to ThreadMain.  This structure is allocated on the stack
  38 // from within StartWithOptions.
  39 struct Thread::StartupData {
  40   // We get away with a const reference here because of how we are allocated.
  41   const Thread::Options& options;
  42
  43   // Used to synchronize thread startup.
  44   WaitableEvent event;
  45
  46   explicit StartupData(const Options& opt)
  47       : options(opt),
  48         event(false, false) {}
  49 };
  50
  51 Thread::Thread(const char* name)
  52     :
  53 #if defined(OS_WIN)
  54       com_status_(NONE),
  55 #endif
  56       started_(false),
  57       stopping_(false),
  58       running_(false),
  59       startup_data_(NULL),
  60       thread_(0),
  61       message_loop_(NULL),
  62       thread_id_(kInvalidThreadId),
  63       name_(name) {
  64 }
  65
  66 Thread::~Thread() {
  67   Stop();
  68 }
  69
  70 bool Thread::Start() {
  71   Options options;
  72 #if defined(OS_WIN)
  73   if (com_status_ == STA)
  74     options.message_loop_type = MessageLoop::TYPE_UI;
  75 #endif
  76   return StartWithOptions(options);
  77 }
  78
  79 bool Thread::StartWithOptions(const Options& options) {
  80   DCHECK(!message_loop_);
  81 #if defined(OS_WIN)
  82   DCHECK((com_status_ != STA) ||
  83       (options.message_loop_type == MessageLoop::TYPE_UI));
  84 #endif
  85
  86   SetThreadWasQuitProperly(false);
  87
  88   StartupData startup_data(options);
  89   startup_data_ = &startup_data;
  90
  91   if (!PlatformThread::Create(options.stack_size, this, &thread_)) {
  92     DLOG(ERROR) << "failed to create thread";
  93     startup_data_ = NULL;
  94     return false;
  95   }
  96
  97   // Wait for the thread to start and initialize message_loop_
  98   base::ThreadRestrictions::ScopedAllowWait allow_wait;
  99   startup_data.event.Wait();
 100
 101   // set it to NULL so we don't keep a pointer to some object on the stack.
 102   startup_data_ = NULL;
 103   started_ = true;
 104
 105   DCHECK(message_loop_);
 106   return true;
 107 }
 108
 109 void Thread::Stop() {
 110   if (!started_)
 111     return;
 112
 113   StopSoon();
 114
 115   // Wait for the thread to exit.
 116   //
 117   // TODO(darin): Unfortunately, we need to keep message_loop_ around until
 118   // the thread exits.  Some consumers are abusing the API.  Make them stop.
 119   //
 120   PlatformThread::Join(thread_);
 121
 122   // The thread should NULL message_loop_ on exit.
 123   DCHECK(!message_loop_);
 124
 125   // The thread no longer needs to be joined.
 126   started_ = false;
 127
 128   stopping_ = false;
 129 }
 130
 131 void Thread::StopSoon() {
 132   // We should only be called on the same thread that started us.
 133
 134   // Reading thread_id_ without a lock can lead to a benign data race
 135   // with ThreadMain, so we annotate it to stay silent under ThreadSanitizer.
 136   DCHECK_NE(ANNOTATE_UNPROTECTED_READ(thread_id_), PlatformThread::CurrentId());
 137
 138   if (stopping_ || !message_loop_)
 139     return;
 140
 141   stopping_ = true;
 142   message_loop_->PostTask(FROM_HERE, base::Bind(&ThreadQuitHelper));
 143 }
 144
 145 bool Thread::IsRunning() const {
 146   return running_;
 147 }
 148
 149 void Thread::Run(MessageLoop* message_loop) {
 150   message_loop->Run();
 151 }
 152
 153 void Thread::SetThreadWasQuitProperly(bool flag) {
 154   lazy_tls_bool.Pointer()->Set(flag);
 155 }
 156
 157 bool Thread::GetThreadWasQuitProperly() {
 158   bool quit_properly = true;
 159 #ifndef NDEBUG
 160   quit_properly = lazy_tls_bool.Pointer()->Get();
 161 #endif
 162   return quit_properly;
 163 }
 164
 165 void Thread::ThreadMain() {
 166   {
 167     // The message loop for this thread.
 168     MessageLoop message_loop(startup_data_->options.message_loop_type);
 169
 170     // Complete the initialization of our Thread object.
 171     thread_id_ = PlatformThread::CurrentId();
 172     PlatformThread::SetName(name_.c_str());
 173     ANNOTATE_THREAD_NAME(name_.c_str());  // Tell the name to race detector.
 174     message_loop.set_thread_name(name_);
 175     message_loop_ = &message_loop;
 176
 177 #if defined(OS_WIN)
 178     scoped_ptr<win::ScopedCOMInitializer> com_initializer;
 179     if (com_status_ != NONE) {
 180       com_initializer.reset((com_status_ == STA) ?
 181           new win::ScopedCOMInitializer() :
 182           new win::ScopedCOMInitializer(win::ScopedCOMInitializer::kMTA));
 183     }
 184 #endif
 185
 186     // Let the thread do extra initialization.
 187     // Let's do this before signaling we are started.
 188     Init();
 189
 190     running_ = true;
 191     startup_data_->event.Signal();
 192     // startup_data_ can't be touched anymore since the starting thread is now
 193     // unlocked.
 194
 195     Run(message_loop_);
 196     running_ = false;
 197
 198     // Let the thread do extra cleanup.
 199     CleanUp();
 200
 201 #if defined(OS_WIN)
 202     com_initializer.reset();
 203 #endif
 204
 205     // Assert that MessageLoop::Quit was called by ThreadQuitHelper.
 206     DCHECK(GetThreadWasQuitProperly());
 207
 208     // We can't receive messages anymore.
 209     message_loop_ = NULL;
 210   }
 211 }
 212
 213 }  // namespace base