Home | History | Annotate | Download | only in threading 
      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_id_name_manager.h"
     11 #include "base/threading/thread_local.h"
     12 #include "base/threading/thread_restrictions.h"
     13 #include "base/synchronization/waitable_event.h"
     14 
     15 #if defined(OS_WIN)
     16 #include "base/win/scoped_com_initializer.h"
     17 #endif
     18 
     19 namespace base {
     20 
     21 namespace {
     22 
     23 // We use this thread-local variable to record whether or not a thread exited
     24 // because its Stop method was called.  This allows us to catch cases where
     25 // MessageLoop::QuitWhenIdle() is called directly, which is unexpected when
     26 // using a Thread to setup and run a MessageLoop.
     27 base::LazyInstance<base::ThreadLocalBoolean> lazy_tls_bool =
     28     LAZY_INSTANCE_INITIALIZER;
     29 
     30 }  // namespace
     31 
     32 // This is used to trigger the message loop to exit.
     33 void ThreadQuitHelper() {
     34   MessageLoop::current()->QuitWhenIdle();
     35   Thread::SetThreadWasQuitProperly(true);
     36 }
     37 
     38 // Used to pass data to ThreadMain.  This structure is allocated on the stack
     39 // from within StartWithOptions.
     40 struct Thread::StartupData {
     41   // We get away with a const reference here because of how we are allocated.
     42   const Thread::Options& options;
     43 
     44   // Used to synchronize thread startup.
     45   WaitableEvent event;
     46 
     47   explicit StartupData(const Options& opt)
     48       : options(opt),
     49         event(false, false) {}
     50 };
     51 
     52 Thread::Thread(const char* name)
     53     :
     54 #if defined(OS_WIN)
     55       com_status_(NONE),
     56 #endif
     57       started_(false),
     58       stopping_(false),
     59       running_(false),
     60       startup_data_(NULL),
     61       thread_(0),
     62       message_loop_(NULL),
     63       thread_id_(kInvalidThreadId),
     64       name_(name) {
     65 }
     66 
     67 Thread::~Thread() {
     68   Stop();
     69 }
     70 
     71 bool Thread::Start() {
     72   Options options;
     73 #if defined(OS_WIN)
     74   if (com_status_ == STA)
     75     options.message_loop_type = MessageLoop::TYPE_UI;
     76 #endif
     77   return StartWithOptions(options);
     78 }
     79 
     80 bool Thread::StartWithOptions(const Options& options) {
     81   DCHECK(!message_loop_);
     82 #if defined(OS_WIN)
     83   DCHECK((com_status_ != STA) ||
     84       (options.message_loop_type == MessageLoop::TYPE_UI));
     85 #endif
     86 
     87   SetThreadWasQuitProperly(false);
     88 
     89   StartupData startup_data(options);
     90   startup_data_ = &startup_data;
     91 
     92   if (!PlatformThread::Create(options.stack_size, this, &thread_)) {
     93     DLOG(ERROR) << "failed to create thread";
     94     startup_data_ = NULL;
     95     return false;
     96   }
     97 
     98   // Wait for the thread to start and initialize message_loop_
     99   base::ThreadRestrictions::ScopedAllowWait allow_wait;
    100   startup_data.event.Wait();
    101 
    102   // set it to NULL so we don't keep a pointer to some object on the stack.
    103   startup_data_ = NULL;
    104   started_ = true;
    105 
    106   DCHECK(message_loop_);
    107   return true;
    108 }
    109 
    110 void Thread::Stop() {
    111   if (!started_)
    112     return;
    113 
    114   StopSoon();
    115 
    116   // Wait for the thread to exit.
    117   //
    118   // TODO(darin): Unfortunately, we need to keep message_loop_ around until
    119   // the thread exits.  Some consumers are abusing the API.  Make them stop.
    120   //
    121   PlatformThread::Join(thread_);
    122 
    123   // The thread should NULL message_loop_ on exit.
    124   DCHECK(!message_loop_);
    125 
    126   // The thread no longer needs to be joined.
    127   started_ = false;
    128 
    129   stopping_ = false;
    130 }
    131 
    132 void Thread::StopSoon() {
    133   // We should only be called on the same thread that started us.
    134 
    135   // Reading thread_id_ without a lock can lead to a benign data race
    136   // with ThreadMain, so we annotate it to stay silent under ThreadSanitizer.
    137   DCHECK_NE(ANNOTATE_UNPROTECTED_READ(thread_id_), PlatformThread::CurrentId());
    138 
    139   if (stopping_ || !message_loop_)
    140     return;
    141 
    142   stopping_ = true;
    143   message_loop_->PostTask(FROM_HERE, base::Bind(&ThreadQuitHelper));
    144 }
    145 
    146 bool Thread::IsRunning() const {
    147   return running_;
    148 }
    149 
    150 void Thread::SetPriority(ThreadPriority priority) {
    151   // The thread must be started (and id known) for this to be
    152   // compatible with all platforms.
    153   DCHECK_NE(thread_id_, kInvalidThreadId);
    154   PlatformThread::SetThreadPriority(thread_, priority);
    155 }
    156 
    157 void Thread::Run(MessageLoop* message_loop) {
    158   message_loop->Run();
    159 }
    160 
    161 void Thread::SetThreadWasQuitProperly(bool flag) {
    162   lazy_tls_bool.Pointer()->Set(flag);
    163 }
    164 
    165 bool Thread::GetThreadWasQuitProperly() {
    166   bool quit_properly = true;
    167 #ifndef NDEBUG
    168   quit_properly = lazy_tls_bool.Pointer()->Get();
    169 #endif
    170   return quit_properly;
    171 }
    172 
    173 void Thread::ThreadMain() {
    174   {
    175     // The message loop for this thread.
    176     MessageLoop message_loop(startup_data_->options.message_loop_type);
    177 
    178     // Complete the initialization of our Thread object.
    179     thread_id_ = PlatformThread::CurrentId();
    180     PlatformThread::SetName(name_.c_str());
    181     ANNOTATE_THREAD_NAME(name_.c_str());  // Tell the name to race detector.
    182     message_loop.set_thread_name(name_);
    183     message_loop_ = &message_loop;
    184 
    185 #if defined(OS_WIN)
    186     scoped_ptr<win::ScopedCOMInitializer> com_initializer;
    187     if (com_status_ != NONE) {
    188       com_initializer.reset((com_status_ == STA) ?
    189           new win::ScopedCOMInitializer() :
    190           new win::ScopedCOMInitializer(win::ScopedCOMInitializer::kMTA));
    191     }
    192 #endif
    193 
    194     // Let the thread do extra initialization.
    195     // Let's do this before signaling we are started.
    196     Init();
    197 
    198     running_ = true;
    199     startup_data_->event.Signal();
    200     // startup_data_ can't be touched anymore since the starting thread is now
    201     // unlocked.
    202 
    203     Run(message_loop_);
    204     running_ = false;
    205 
    206     // Let the thread do extra cleanup.
    207     CleanUp();
    208 
    209 #if defined(OS_WIN)
    210     com_initializer.reset();
    211 #endif
    212 
    213     // Assert that MessageLoop::Quit was called by ThreadQuitHelper.
    214     DCHECK(GetThreadWasQuitProperly());
    215 
    216     // We can't receive messages anymore.
    217     message_loop_ = NULL;
    218   }
    219 }
    220 
    221 }  // namespace base
    222