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/string_util.h"
   9 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
  10 #include "base/thread_local.h"
  11 #include "base/waitable_event.h"
  12
  13 namespace base {
  14
  15 // This task is used to trigger the message loop to exit.
  16 class ThreadQuitTask : public Task {
  17  public:
  18   virtual void Run() {
  19     MessageLoop::current()->Quit();
  20     Thread::SetThreadWasQuitProperly(true);
  21   }
  22 };
  23
  24 // Used to pass data to ThreadMain.  This structure is allocated on the stack
  25 // from within StartWithOptions.
  26 struct Thread::StartupData {
  27   // We get away with a const reference here because of how we are allocated.
  28   const Thread::Options& options;
  29
  30   // Used to synchronize thread startup.
  31   WaitableEvent event;
  32
  33   explicit StartupData(const Options& opt)
  34       : options(opt),
  35         event(false, false) {}
  36 };
  37
  38 Thread::Thread(const char* name)
  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;  // Record that we failed to start.
  89     return false;
  90   }
  91
  92   // Wait for the thread to start and initialize message_loop_
  93   startup_data.event.Wait();
  94
  95   DCHECK(message_loop_);
  96   return true;
  97 }
  98
  99 void Thread::Stop() {
 100   if (!thread_was_started())
 101     return;
 102
 103   StopSoon();
 104
 105   // Wait for the thread to exit.
 106   //
 107   // TODO(darin): Unfortunately, we need to keep message_loop_ around until
 108   // the thread exits.  Some consumers are abusing the API.  Make them stop.
 109   //
 110   PlatformThread::Join(thread_);
 111
 112   // The thread should NULL message_loop_ on exit.
 113   DCHECK(!message_loop_);
 114
 115   // The thread no longer needs to be joined.
 116   startup_data_ = NULL;
 117
 118   stopping_ = false;
 119 }
 120
 121 void Thread::StopSoon() {
 122   // We should only be called on the same thread that started us.
 123
 124   // Reading thread_id_ without a lock can lead to a benign data race
 125   // with ThreadMain, so we annotate it to stay silent under ThreadSanitizer.
 126   DCHECK_NE(ANNOTATE_UNPROTECTED_READ(thread_id_), PlatformThread::CurrentId());
 127
 128   if (stopping_ || !message_loop_)
 129     return;
 130
 131   stopping_ = true;
 132   message_loop_->PostTask(FROM_HERE, new ThreadQuitTask());
 133 }
 134
 135 void Thread::Run(MessageLoop* message_loop) {
 136   message_loop->Run();
 137 }
 138
 139 void Thread::ThreadMain() {
 140   {
 141     // The message loop for this thread.
 142     MessageLoop message_loop(startup_data_->options.message_loop_type);
 143
 144     // Complete the initialization of our Thread object.
 145     thread_id_ = PlatformThread::CurrentId();
 146     PlatformThread::SetName(name_.c_str());
 147     ANNOTATE_THREAD_NAME(name_.c_str());  // Tell the name to race detector.
 148     message_loop.set_thread_name(name_);
 149     message_loop_ = &message_loop;
 150     message_loop_proxy_ = MessageLoopProxy::CreateForCurrentThread();
 151
 152     // Let the thread do extra initialization.
 153     // Let's do this before signaling we are started.
 154     Init();
 155
 156     startup_data_->event.Signal();
 157     // startup_data_ can't be touched anymore since the starting thread is now
 158     // unlocked.
 159
 160     Run(message_loop_);
 161
 162     // Let the thread do extra cleanup.
 163     CleanUp();
 164
 165     // Assert that MessageLoop::Quit was called by ThreadQuitTask.
 166     DCHECK(GetThreadWasQuitProperly());
 167
 168     // We can't receive messages anymore.
 169     message_loop_ = NULL;
 170     message_loop_proxy_ = NULL;
 171   }
 172   CleanUpAfterMessageLoopDestruction();
 173   thread_id_ = 0;
 174 }
 175
 176 }  // namespace base