content/child/child_thread.cc

   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 "content/child/child_thread.h"
   6
   7 #include <signal.h>
   8
   9 #include <string>
  10
  11 #include "base/allocator/allocator_extension.h"
  12 #include "base/base_switches.h"
  13 #include "base/basictypes.h"
  14 #include "base/command_line.h"
  15 #include "base/debug/leak_annotations.h"
  16 #include "base/lazy_instance.h"
  17 #include "base/logging.h"
  18 #include "base/message_loop/message_loop.h"
  19 #include "base/message_loop/timer_slack.h"
  20 #include "base/process/kill.h"
  21 #include "base/process/process_handle.h"
  22 #include "base/strings/string_number_conversions.h"
  23 #include "base/strings/string_util.h"
  24 #include "base/synchronization/condition_variable.h"
  25 #include "base/synchronization/lock.h"
  26 #include "base/threading/thread_local.h"
  27 #include "base/tracked_objects.h"
  28 #include "components/tracing/child_trace_message_filter.h"
  29 #include "content/child/bluetooth/bluetooth_message_filter.h"
  30 #include "content/child/child_discardable_shared_memory_manager.h"
  31 #include "content/child/child_gpu_memory_buffer_manager.h"
  32 #include "content/child/child_histogram_message_filter.h"
  33 #include "content/child/child_process.h"
  34 #include "content/child/child_resource_message_filter.h"
  35 #include "content/child/child_shared_bitmap_manager.h"
  36 #include "content/child/fileapi/file_system_dispatcher.h"
  37 #include "content/child/fileapi/webfilesystem_impl.h"
  38 #include "content/child/geofencing/geofencing_message_filter.h"
  39 #include "content/child/mojo/mojo_application.h"
  40 #include "content/child/navigator_connect/navigator_connect_dispatcher.h"
  41 #include "content/child/notifications/notification_dispatcher.h"
  42 #include "content/child/power_monitor_broadcast_source.h"
  43 #include "content/child/push_messaging/push_dispatcher.h"
  44 #include "content/child/quota_dispatcher.h"
  45 #include "content/child/quota_message_filter.h"
  46 #include "content/child/resource_dispatcher.h"
  47 #include "content/child/service_worker/service_worker_message_filter.h"
  48 #include "content/child/thread_safe_sender.h"
  49 #include "content/child/websocket_dispatcher.h"
  50 #include "content/common/child_process_messages.h"
  51 #include "content/public/common/content_switches.h"
  52 #include "ipc/ipc_logging.h"
  53 #include "ipc/ipc_switches.h"
  54 #include "ipc/ipc_sync_channel.h"
  55 #include "ipc/ipc_sync_message_filter.h"
  56 #include "ipc/mojo/ipc_channel_mojo.h"
  57
  58 #if defined(OS_WIN)
  59 #include "content/common/handle_enumerator_win.h"
  60 #endif
  61
  62 #if defined(TCMALLOC_TRACE_MEMORY_SUPPORTED)
  63 #include "third_party/tcmalloc/chromium/src/gperftools/heap-profiler.h"
  64 #endif
  65
  66 using tracked_objects::ThreadData;
  67
  68 namespace content {
  69 namespace {
  70
  71 // How long to wait for a connection to the browser process before giving up.
  72 const int kConnectionTimeoutS = 15;
  73
  74 base::LazyInstance<base::ThreadLocalPointer<ChildThread> > g_lazy_tls =
  75     LAZY_INSTANCE_INITIALIZER;
  76
  77 // This isn't needed on Windows because there the sandbox's job object
  78 // terminates child processes automatically. For unsandboxed processes (i.e.
  79 // plugins), PluginThread has EnsureTerminateMessageFilter.
  80 #if defined(OS_POSIX)
  81
  82 // TODO(earthdok): Re-enable on CrOS http://crbug.com/360622
  83 #if (defined(ADDRESS_SANITIZER) || defined(LEAK_SANITIZER) || \
  84     defined(THREAD_SANITIZER)) && !defined(OS_CHROMEOS)
  85 // A thread delegate that waits for |duration| and then exits the process with
  86 // _exit(0).
  87 class WaitAndExitDelegate : public base::PlatformThread::Delegate {
  88  public:
  89   explicit WaitAndExitDelegate(base::TimeDelta duration)
  90       : duration_(duration) {}
  91
  92   void ThreadMain() override {
  93     base::PlatformThread::Sleep(duration_);
  94     _exit(0);
  95   }
  96
  97  private:
  98   const base::TimeDelta duration_;
  99   DISALLOW_COPY_AND_ASSIGN(WaitAndExitDelegate);
 100 };
 101
 102 bool CreateWaitAndExitThread(base::TimeDelta duration) {
 103   scoped_ptr<WaitAndExitDelegate> delegate(new WaitAndExitDelegate(duration));
 104
 105   const bool thread_created =
 106       base::PlatformThread::CreateNonJoinable(0, delegate.get());
 107   if (!thread_created)
 108     return false;
 109
 110   // A non joinable thread has been created. The thread will either terminate
 111   // the process or will be terminated by the process. Therefore, keep the
 112   // delegate object alive for the lifetime of the process.
 113   WaitAndExitDelegate* leaking_delegate = delegate.release();
 114   ANNOTATE_LEAKING_OBJECT_PTR(leaking_delegate);
 115   ignore_result(leaking_delegate);
 116   return true;
 117 }
 118 #endif
 119
 120 class SuicideOnChannelErrorFilter : public IPC::MessageFilter {
 121  public:
 122   // IPC::MessageFilter
 123   void OnChannelError() override {
 124     // For renderer/worker processes:
 125     // On POSIX, at least, one can install an unload handler which loops
 126     // forever and leave behind a renderer process which eats 100% CPU forever.
 127     //
 128     // This is because the terminate signals (ViewMsg_ShouldClose and the error
 129     // from the IPC sender) are routed to the main message loop but never
 130     // processed (because that message loop is stuck in V8).
 131     //
 132     // One could make the browser SIGKILL the renderers, but that leaves open a
 133     // large window where a browser failure (or a user, manually terminating
 134     // the browser because "it's stuck") will leave behind a process eating all
 135     // the CPU.
 136     //
 137     // So, we install a filter on the sender so that we can process this event
 138     // here and kill the process.
 139     // TODO(earthdok): Re-enable on CrOS http://crbug.com/360622
 140 #if (defined(ADDRESS_SANITIZER) || defined(LEAK_SANITIZER) || \
 141     defined(THREAD_SANITIZER)) && !defined(OS_CHROMEOS)
 142     // Some sanitizer tools rely on exit handlers (e.g. to run leak detection,
 143     // or dump code coverage data to disk). Instead of exiting the process
 144     // immediately, we give it 60 seconds to run exit handlers.
 145     CHECK(CreateWaitAndExitThread(base::TimeDelta::FromSeconds(60)));
 146 #if defined(LEAK_SANITIZER)
 147     // Invoke LeakSanitizer early to avoid detecting shutdown-only leaks. If
 148     // leaks are found, the process will exit here.
 149     __lsan_do_leak_check();
 150 #endif
 151 #else
 152     _exit(0);
 153 #endif
 154   }
 155
 156  protected:
 157   ~SuicideOnChannelErrorFilter() override {}
 158 };
 159
 160 #endif  // OS(POSIX)
 161
 162 #if defined(OS_ANDROID)
 163 ChildThread* g_child_thread = NULL;
 164
 165 // A lock protects g_child_thread.
 166 base::LazyInstance<base::Lock> g_lazy_child_thread_lock =
 167     LAZY_INSTANCE_INITIALIZER;
 168
 169 // base::ConditionVariable has an explicit constructor that takes
 170 // a base::Lock pointer as parameter. The base::DefaultLazyInstanceTraits
 171 // doesn't handle the case. Thus, we need our own class here.
 172 struct CondVarLazyInstanceTraits {
 173   static const bool kRegisterOnExit = true;
 174 #ifndef NDEBUG
 175   static const bool kAllowedToAccessOnNonjoinableThread = false;
 176 #endif
 177
 178   static base::ConditionVariable* New(void* instance) {
 179     return new (instance) base::ConditionVariable(
 180         g_lazy_child_thread_lock.Pointer());
 181   }
 182   static void Delete(base::ConditionVariable* instance) {
 183     instance->~ConditionVariable();
 184   }
 185 };
 186
 187 // A condition variable that synchronize threads initializing and waiting
 188 // for g_child_thread.
 189 base::LazyInstance<base::ConditionVariable, CondVarLazyInstanceTraits>
 190     g_lazy_child_thread_cv = LAZY_INSTANCE_INITIALIZER;
 191
 192 void QuitMainThreadMessageLoop() {
 193   base::MessageLoop::current()->Quit();
 194 }
 195
 196 #endif
 197
 198 }  // namespace
 199
 200 ChildThread::Options::Options()
 201     : channel_name(base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
 202           switches::kProcessChannelID)),
 203       use_mojo_channel(false) {}
 204
 205 ChildThread::Options::Options(bool mojo)
 206     : channel_name(base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
 207           switches::kProcessChannelID)),
 208       use_mojo_channel(mojo) {}
 209
 210
 211 ChildThread::ChildThreadMessageRouter::ChildThreadMessageRouter(
 212     IPC::Sender* sender)
 213     : sender_(sender) {}
 214
 215 bool ChildThread::ChildThreadMessageRouter::Send(IPC::Message* msg) {
 216   return sender_->Send(msg);
 217 }
 218
 219 ChildThread::ChildThread()
 220     : router_(this),
 221       in_browser_process_(false),
 222       channel_connected_factory_(this) {
 223   Init(Options());
 224 }
 225
 226 ChildThread::ChildThread(const Options& options)
 227     : router_(this),
 228       in_browser_process_(true),
 229       channel_connected_factory_(this) {
 230   Init(options);
 231 }
 232
 233 scoped_ptr<IPC::SyncChannel> ChildThread::CreateChannel(bool use_mojo_channel) {
 234   if (use_mojo_channel) {
 235     VLOG(1) << "Mojo is enabled on child";
 236     return IPC::SyncChannel::Create(
 237         IPC::ChannelMojo::CreateClientFactory(channel_name_),
 238         this,
 239         ChildProcess::current()->io_message_loop_proxy(),
 240         true,
 241         ChildProcess::current()->GetShutDownEvent());
 242   }
 243
 244   VLOG(1) << "Mojo is disabled on child";
 245   return IPC::SyncChannel::Create(
 246       channel_name_,
 247       IPC::Channel::MODE_CLIENT,
 248       this,
 249       ChildProcess::current()->io_message_loop_proxy(),
 250       true,
 251       ChildProcess::current()->GetShutDownEvent());
 252 }
 253
 254 void ChildThread::Init(const Options& options) {
 255   channel_name_ = options.channel_name;
 256
 257   g_lazy_tls.Pointer()->Set(this);
 258   on_channel_error_called_ = false;
 259   message_loop_ = base::MessageLoop::current();
 260 #ifdef IPC_MESSAGE_LOG_ENABLED
 261   // We must make sure to instantiate the IPC Logger *before* we create the
 262   // channel, otherwise we can get a callback on the IO thread which creates
 263   // the logger, and the logger does not like being created on the IO thread.
 264   IPC::Logging::GetInstance();
 265 #endif
 266   channel_ = CreateChannel(options.use_mojo_channel);
 267 #ifdef IPC_MESSAGE_LOG_ENABLED
 268   if (!in_browser_process_)
 269     IPC::Logging::GetInstance()->SetIPCSender(this);
 270 #endif
 271
 272   mojo_application_.reset(new MojoApplication);
 273
 274   sync_message_filter_ =
 275       new IPC::SyncMessageFilter(ChildProcess::current()->GetShutDownEvent());
 276   thread_safe_sender_ = new ThreadSafeSender(
 277       base::MessageLoopProxy::current().get(), sync_message_filter_.get());
 278
 279   resource_dispatcher_.reset(new ResourceDispatcher(
 280       this, message_loop()->task_runner()));
 281   websocket_dispatcher_.reset(new WebSocketDispatcher);
 282   file_system_dispatcher_.reset(new FileSystemDispatcher());
 283
 284   histogram_message_filter_ = new ChildHistogramMessageFilter();
 285   resource_message_filter_ =
 286       new ChildResourceMessageFilter(resource_dispatcher());
 287
 288   service_worker_message_filter_ =
 289       new ServiceWorkerMessageFilter(thread_safe_sender_.get());
 290
 291   quota_message_filter_ =
 292       new QuotaMessageFilter(thread_safe_sender_.get());
 293   quota_dispatcher_.reset(new QuotaDispatcher(thread_safe_sender_.get(),
 294                                               quota_message_filter_.get()));
 295   geofencing_message_filter_ =
 296       new GeofencingMessageFilter(thread_safe_sender_.get());
 297   bluetooth_message_filter_ =
 298       new BluetoothMessageFilter(thread_safe_sender_.get());
 299   notification_dispatcher_ =
 300       new NotificationDispatcher(thread_safe_sender_.get());
 301   push_dispatcher_ = new PushDispatcher(thread_safe_sender_.get());
 302   navigator_connect_dispatcher_ =
 303       new NavigatorConnectDispatcher(thread_safe_sender_.get());
 304
 305   channel_->AddFilter(histogram_message_filter_.get());
 306   channel_->AddFilter(sync_message_filter_.get());
 307   channel_->AddFilter(resource_message_filter_.get());
 308   channel_->AddFilter(quota_message_filter_->GetFilter());
 309   channel_->AddFilter(notification_dispatcher_->GetFilter());
 310   channel_->AddFilter(push_dispatcher_->GetFilter());
 311   channel_->AddFilter(service_worker_message_filter_->GetFilter());
 312   channel_->AddFilter(geofencing_message_filter_->GetFilter());
 313   channel_->AddFilter(bluetooth_message_filter_->GetFilter());
 314   channel_->AddFilter(navigator_connect_dispatcher_->GetFilter());
 315
 316   if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
 317           switches::kSingleProcess)) {
 318     // In single process mode, browser-side tracing will cover the whole
 319     // process including renderers.
 320     channel_->AddFilter(new tracing::ChildTraceMessageFilter(
 321         ChildProcess::current()->io_message_loop_proxy()));
 322   }
 323
 324   // In single process mode we may already have a power monitor
 325   if (!base::PowerMonitor::Get()) {
 326     scoped_ptr<PowerMonitorBroadcastSource> power_monitor_source(
 327       new PowerMonitorBroadcastSource());
 328     channel_->AddFilter(power_monitor_source->GetMessageFilter());
 329
 330     power_monitor_.reset(new base::PowerMonitor(
 331         power_monitor_source.Pass()));
 332   }
 333
 334 #if defined(OS_POSIX)
 335   // Check that --process-type is specified so we don't do this in unit tests
 336   // and single-process mode.
 337   if (base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kProcessType))
 338     channel_->AddFilter(new SuicideOnChannelErrorFilter());
 339 #endif
 340
 341   int connection_timeout = kConnectionTimeoutS;
 342   std::string connection_override =
 343       base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
 344           switches::kIPCConnectionTimeout);
 345   if (!connection_override.empty()) {
 346     int temp;
 347     if (base::StringToInt(connection_override, &temp))
 348       connection_timeout = temp;
 349   }
 350
 351   base::MessageLoop::current()->PostDelayedTask(
 352       FROM_HERE,
 353       base::Bind(&ChildThread::EnsureConnected,
 354                  channel_connected_factory_.GetWeakPtr()),
 355       base::TimeDelta::FromSeconds(connection_timeout));
 356
 357 #if defined(OS_ANDROID)
 358   {
 359     base::AutoLock lock(g_lazy_child_thread_lock.Get());
 360     g_child_thread = this;
 361   }
 362   // Signalling without locking is fine here because only
 363   // one thread can wait on the condition variable.
 364   g_lazy_child_thread_cv.Get().Signal();
 365 #endif
 366
 367 #if defined(TCMALLOC_TRACE_MEMORY_SUPPORTED)
 368   trace_memory_controller_.reset(new base::debug::TraceMemoryController(
 369       message_loop_->message_loop_proxy(),
 370       ::HeapProfilerWithPseudoStackStart,
 371       ::HeapProfilerStop,
 372       ::GetHeapProfile));
 373 #endif
 374
 375   shared_bitmap_manager_.reset(
 376       new ChildSharedBitmapManager(thread_safe_sender()));
 377
 378   gpu_memory_buffer_manager_.reset(
 379       new ChildGpuMemoryBufferManager(thread_safe_sender()));
 380
 381   discardable_shared_memory_manager_.reset(
 382       new ChildDiscardableSharedMemoryManager(thread_safe_sender()));
 383 }
 384
 385 ChildThread::~ChildThread() {
 386 #ifdef IPC_MESSAGE_LOG_ENABLED
 387   IPC::Logging::GetInstance()->SetIPCSender(NULL);
 388 #endif
 389
 390   channel_->RemoveFilter(histogram_message_filter_.get());
 391   channel_->RemoveFilter(sync_message_filter_.get());
 392
 393   // The ChannelProxy object caches a pointer to the IPC thread, so need to
 394   // reset it as it's not guaranteed to outlive this object.
 395   // NOTE: this also has the side-effect of not closing the main IPC channel to
 396   // the browser process.  This is needed because this is the signal that the
 397   // browser uses to know that this process has died, so we need it to be alive
 398   // until this process is shut down, and the OS closes the handle
 399   // automatically.  We used to watch the object handle on Windows to do this,
 400   // but it wasn't possible to do so on POSIX.
 401   channel_->ClearIPCTaskRunner();
 402   g_lazy_tls.Pointer()->Set(NULL);
 403 }
 404
 405 void ChildThread::Shutdown() {
 406   // Delete objects that hold references to blink so derived classes can
 407   // safely shutdown blink in their Shutdown implementation.
 408   file_system_dispatcher_.reset();
 409   quota_dispatcher_.reset();
 410   WebFileSystemImpl::DeleteThreadSpecificInstance();
 411 }
 412
 413 void ChildThread::OnChannelConnected(int32 peer_pid) {
 414   channel_connected_factory_.InvalidateWeakPtrs();
 415 }
 416
 417 void ChildThread::OnChannelError() {
 418   set_on_channel_error_called(true);
 419   base::MessageLoop::current()->Quit();
 420 }
 421
 422 bool ChildThread::Send(IPC::Message* msg) {
 423   DCHECK(base::MessageLoop::current() == message_loop());
 424   if (!channel_) {
 425     delete msg;
 426     return false;
 427   }
 428
 429   return channel_->Send(msg);
 430 }
 431
 432 MessageRouter* ChildThread::GetRouter() {
 433   DCHECK(base::MessageLoop::current() == message_loop());
 434   return &router_;
 435 }
 436
 437 scoped_ptr<base::SharedMemory> ChildThread::AllocateSharedMemory(
 438     size_t buf_size) {
 439   DCHECK(base::MessageLoop::current() == message_loop());
 440   return AllocateSharedMemory(buf_size, this);
 441 }
 442
 443 // static
 444 scoped_ptr<base::SharedMemory> ChildThread::AllocateSharedMemory(
 445     size_t buf_size,
 446     IPC::Sender* sender) {
 447   scoped_ptr<base::SharedMemory> shared_buf;
 448 #if defined(OS_WIN)
 449   shared_buf.reset(new base::SharedMemory);
 450   if (!shared_buf->CreateAnonymous(buf_size)) {
 451     NOTREACHED();
 452     return NULL;
 453   }
 454 #else
 455   // On POSIX, we need to ask the browser to create the shared memory for us,
 456   // since this is blocked by the sandbox.
 457   base::SharedMemoryHandle shared_mem_handle;
 458   if (sender->Send(new ChildProcessHostMsg_SyncAllocateSharedMemory(
 459                            buf_size, &shared_mem_handle))) {
 460     if (base::SharedMemory::IsHandleValid(shared_mem_handle)) {
 461       shared_buf.reset(new base::SharedMemory(shared_mem_handle, false));
 462     } else {
 463       NOTREACHED() << "Browser failed to allocate shared memory";
 464       return NULL;
 465     }
 466   } else {
 467     NOTREACHED() << "Browser allocation request message failed";
 468     return NULL;
 469   }
 470 #endif
 471   return shared_buf;
 472 }
 473
 474 bool ChildThread::OnMessageReceived(const IPC::Message& msg) {
 475   if (mojo_application_->OnMessageReceived(msg))
 476     return true;
 477
 478   // Resource responses are sent to the resource dispatcher.
 479   if (resource_dispatcher_->OnMessageReceived(msg))
 480     return true;
 481   if (websocket_dispatcher_->OnMessageReceived(msg))
 482     return true;
 483   if (file_system_dispatcher_->OnMessageReceived(msg))
 484     return true;
 485
 486   bool handled = true;
 487   IPC_BEGIN_MESSAGE_MAP(ChildThread, msg)
 488     IPC_MESSAGE_HANDLER(ChildProcessMsg_Shutdown, OnShutdown)
 489 #if defined(IPC_MESSAGE_LOG_ENABLED)
 490     IPC_MESSAGE_HANDLER(ChildProcessMsg_SetIPCLoggingEnabled,
 491                         OnSetIPCLoggingEnabled)
 492 #endif
 493     IPC_MESSAGE_HANDLER(ChildProcessMsg_SetProfilerStatus,
 494                         OnSetProfilerStatus)
 495     IPC_MESSAGE_HANDLER(ChildProcessMsg_GetChildProfilerData,
 496                         OnGetChildProfilerData)
 497     IPC_MESSAGE_HANDLER(ChildProcessMsg_DumpHandles, OnDumpHandles)
 498     IPC_MESSAGE_HANDLER(ChildProcessMsg_SetProcessBackgrounded,
 499                         OnProcessBackgrounded)
 500 #if defined(USE_TCMALLOC)
 501     IPC_MESSAGE_HANDLER(ChildProcessMsg_GetTcmallocStats, OnGetTcmallocStats)
 502 #endif
 503     IPC_MESSAGE_UNHANDLED(handled = false)
 504   IPC_END_MESSAGE_MAP()
 505
 506   if (handled)
 507     return true;
 508
 509   if (msg.routing_id() == MSG_ROUTING_CONTROL)
 510     return OnControlMessageReceived(msg);
 511
 512   return router_.OnMessageReceived(msg);
 513 }
 514
 515 bool ChildThread::OnControlMessageReceived(const IPC::Message& msg) {
 516   return false;
 517 }
 518
 519 void ChildThread::OnShutdown() {
 520   base::MessageLoop::current()->Quit();
 521 }
 522
 523 #if defined(IPC_MESSAGE_LOG_ENABLED)
 524 void ChildThread::OnSetIPCLoggingEnabled(bool enable) {
 525   if (enable)
 526     IPC::Logging::GetInstance()->Enable();
 527   else
 528     IPC::Logging::GetInstance()->Disable();
 529 }
 530 #endif  //  IPC_MESSAGE_LOG_ENABLED
 531
 532 void ChildThread::OnSetProfilerStatus(ThreadData::Status status) {
 533   ThreadData::InitializeAndSetTrackingStatus(status);
 534 }
 535
 536 void ChildThread::OnGetChildProfilerData(int sequence_number) {
 537   tracked_objects::ProcessDataSnapshot process_data;
 538   ThreadData::Snapshot(false, &process_data);
 539
 540   Send(new ChildProcessHostMsg_ChildProfilerData(sequence_number,
 541                                                  process_data));
 542 }
 543
 544 void ChildThread::OnDumpHandles() {
 545 #if defined(OS_WIN)
 546   scoped_refptr<HandleEnumerator> handle_enum(
 547       new HandleEnumerator(
 548           base::CommandLine::ForCurrentProcess()->HasSwitch(
 549               switches::kAuditAllHandles)));
 550   handle_enum->EnumerateHandles();
 551   Send(new ChildProcessHostMsg_DumpHandlesDone);
 552 #else
 553   NOTIMPLEMENTED();
 554 #endif
 555 }
 556
 557 #if defined(USE_TCMALLOC)
 558 void ChildThread::OnGetTcmallocStats() {
 559   std::string result;
 560   char buffer[1024 * 32];
 561   base::allocator::GetStats(buffer, sizeof(buffer));
 562   result.append(buffer);
 563   Send(new ChildProcessHostMsg_TcmallocStats(result));
 564 }
 565 #endif
 566
 567 ChildThread* ChildThread::current() {
 568   return g_lazy_tls.Pointer()->Get();
 569 }
 570
 571 #if defined(OS_ANDROID)
 572 // The method must NOT be called on the child thread itself.
 573 // It may block the child thread if so.
 574 void ChildThread::ShutdownThread() {
 575   DCHECK(!ChildThread::current()) <<
 576       "this method should NOT be called from child thread itself";
 577   {
 578     base::AutoLock lock(g_lazy_child_thread_lock.Get());
 579     while (!g_child_thread)
 580       g_lazy_child_thread_cv.Get().Wait();
 581   }
 582   DCHECK_NE(base::MessageLoop::current(), g_child_thread->message_loop());
 583   g_child_thread->message_loop()->PostTask(
 584       FROM_HERE, base::Bind(&QuitMainThreadMessageLoop));
 585 }
 586 #endif
 587
 588 void ChildThread::OnProcessFinalRelease() {
 589   if (on_channel_error_called_) {
 590     base::MessageLoop::current()->Quit();
 591     return;
 592   }
 593
 594   // The child process shutdown sequence is a request response based mechanism,
 595   // where we send out an initial feeler request to the child process host
 596   // instance in the browser to verify if it's ok to shutdown the child process.
 597   // The browser then sends back a response if it's ok to shutdown. This avoids
 598   // race conditions if the process refcount is 0 but there's an IPC message
 599   // inflight that would addref it.
 600   Send(new ChildProcessHostMsg_ShutdownRequest);
 601 }
 602
 603 void ChildThread::EnsureConnected() {
 604   VLOG(0) << "ChildThread::EnsureConnected()";
 605   base::KillProcess(base::GetCurrentProcessHandle(), 0, false);
 606 }
 607
 608 void ChildThread::OnProcessBackgrounded(bool background) {
 609   // Set timer slack to maximum on main thread when in background.
 610   base::TimerSlack timer_slack = base::TIMER_SLACK_NONE;
 611   if (background)
 612     timer_slack = base::TIMER_SLACK_MAXIMUM;
 613   base::MessageLoop::current()->SetTimerSlack(timer_slack);
 614 }
 615
 616 }  // namespace content