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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/thread.h"
      6 
      7 #include "base/dynamic_annotations.h"
      8 #include "base/lazy_instance.h"
      9 #include "base/string_util.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   DCHECK_NE(thread_id_, PlatformThread::CurrentId());
    124 
    125   if (stopping_ || !message_loop_)
    126     return;
    127 
    128   stopping_ = true;
    129   message_loop_->PostTask(FROM_HERE, new ThreadQuitTask());
    130 }
    131 
    132 void Thread::Run(MessageLoop* message_loop) {
    133   message_loop->Run();
    134 }
    135 
    136 void Thread::ThreadMain() {
    137   // The message loop for this thread.
    138   MessageLoop message_loop(startup_data_->options.message_loop_type);
    139 
    140   // Complete the initialization of our Thread object.
    141   thread_id_ = PlatformThread::CurrentId();
    142   PlatformThread::SetName(name_.c_str());
    143   ANNOTATE_THREAD_NAME(name_.c_str());  // Tell the name to race detector.
    144   message_loop.set_thread_name(name_);
    145   message_loop_ = &message_loop;
    146 
    147   // Let the thread do extra initialization.
    148   // Let's do this before signaling we are started.
    149   Init();
    150 
    151   startup_data_->event.Signal();
    152   // startup_data_ can't be touched anymore since the starting thread is now
    153   // unlocked.
    154 
    155   Run(message_loop_);
    156 
    157   // Let the thread do extra cleanup.
    158   CleanUp();
    159 
    160   // Assert that MessageLoop::Quit was called by ThreadQuitTask.
    161   DCHECK(GetThreadWasQuitProperly());
    162 
    163   // We can't receive messages anymore.
    164   message_loop_ = NULL;
    165   thread_id_ = 0;
    166 }
    167 
    168 }  // namespace base
    169