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