base/thread.cc

   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/thread.h"
   6
   7 #include "base/lazy_instance.h"
   8 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
   9 #include "base/thread_local.h"
  10 #include "base/waitable_event.h"
  11
  12 namespace base {
  13
  14 // This task is used to trigger the message loop to exit.
  15 class ThreadQuitTask : public Task {
  16  public:
  17   virtual void Run() {
  18     MessageLoop::current()->Quit();
  19     Thread::SetThreadWasQuitProperly(true);
  20   }
  21 };
  22
  23 // Used to pass data to ThreadMain.  This structure is allocated on the stack
  24 // from within StartWithOptions.
  25 struct Thread::StartupData {
  26   // We get away with a const reference here because of how we are allocated.
  27   const Thread::Options& options;
  28
  29   // Used to synchronize thread startup.
  30   WaitableEvent event;
  31
  32   explicit StartupData(const Options& opt)
  33       : options(opt),
  34         event(false, false) {}
  35 };
  36
  37 Thread::Thread(const char* name)
  38     : started_(false),
  39       stopping_(false),
  40       startup_data_(NULL),
  41       thread_(0),
  42       message_loop_(NULL),
  43       thread_id_(0),
  44       name_(name) {
  45 }
  46
  47 Thread::~Thread() {
  48   Stop();
  49 }
  50
  51 namespace {
  52
  53 // We use this thread-local variable to record whether or not a thread exited
  54 // because its Stop method was called.  This allows us to catch cases where
  55 // MessageLoop::Quit() is called directly, which is unexpected when using a
  56 // Thread to setup and run a MessageLoop.
  57 base::LazyInstance<base::ThreadLocalBoolean> lazy_tls_bool(
  58     base::LINKER_INITIALIZED);
  59
  60 }  // namespace
  61
  62 void Thread::SetThreadWasQuitProperly(bool flag) {
  63   lazy_tls_bool.Pointer()->Set(flag);
  64 }
  65
  66 bool Thread::GetThreadWasQuitProperly() {
  67   bool quit_properly = true;
  68 #ifndef NDEBUG
  69   quit_properly = lazy_tls_bool.Pointer()->Get();
  70 #endif
  71   return quit_properly;
  72 }
  73
  74 bool Thread::Start() {
  75   return StartWithOptions(Options());
  76 }
  77
  78 bool Thread::StartWithOptions(const Options& options) {
  79   DCHECK(!message_loop_);
  80
  81   SetThreadWasQuitProperly(false);
  82
  83   StartupData startup_data(options);
  84   startup_data_ = &startup_data;
  85
  86   if (!PlatformThread::Create(options.stack_size, this, &thread_)) {
  87     DLOG(ERROR) << "failed to create thread";
  88     startup_data_ = NULL;
  89     return false;
  90   }
  91
  92   // Wait for the thread to start and initialize message_loop_
  93   startup_data.event.Wait();
  94
  95   // set it to NULL so we don't keep a pointer to some object on the stack.
  96   startup_data_ = NULL;
  97   started_ = true;
  98
  99   DCHECK(message_loop_);
 100   return true;
 101 }
 102
 103 void Thread::Stop() {
 104   if (!thread_was_started())
 105     return;
 106
 107   StopSoon();
 108
 109   // Wait for the thread to exit.
 110   //
 111   // TODO(darin): Unfortunately, we need to keep message_loop_ around until
 112   // the thread exits.  Some consumers are abusing the API.  Make them stop.
 113   //
 114   PlatformThread::Join(thread_);
 115
 116   // The thread should NULL message_loop_ on exit.
 117   DCHECK(!message_loop_);
 118
 119   // The thread no longer needs to be joined.
 120   started_ = false;
 121
 122   stopping_ = false;
 123 }
 124
 125 void Thread::StopSoon() {
 126   // We should only be called on the same thread that started us.
 127
 128   // Reading thread_id_ without a lock can lead to a benign data race
 129   // with ThreadMain, so we annotate it to stay silent under ThreadSanitizer.
 130   DCHECK_NE(ANNOTATE_UNPROTECTED_READ(thread_id_), PlatformThread::CurrentId());
 131
 132   if (stopping_ || !message_loop_)
 133     return;
 134
 135   stopping_ = true;
 136   message_loop_->PostTask(FROM_HERE, new ThreadQuitTask());
 137 }
 138
 139 void Thread::Run(MessageLoop* message_loop) {
 140   message_loop->Run();
 141 }
 142
 143 void 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_ = 0;
 178 }
 179
 180 }  // namespace base