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      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 
     12 namespace base {
     13 
     14 namespace {
     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.
     20 base::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.
     26 class 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.
     36 struct 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 
     48 Thread::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 
     58 Thread::~Thread() {
     59   Stop();
     60 }
     61 
     62 bool Thread::Start() {
     63   return StartWithOptions(Options());
     64 }
     65 
     66 bool 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 
     91 void 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 
    113 void 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 
    127 void Thread::Run(MessageLoop* message_loop) {
    128   message_loop->Run();
    129 }
    130 
    131 void Thread::SetThreadWasQuitProperly(bool flag) {
    132   lazy_tls_bool.Pointer()->Set(flag);
    133 }
    134 
    135 bool 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 
    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   thread_id_ = kInvalidThreadId;
    177 }
    178 
    179 }  // namespace base
    180