Make ChildThread::current() and ChildProcess::current() only work on the main thread of the child...

content/child/child_thread.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/child/child_thread.h"
 
 #include "base/allocator/allocator_extension.h"
 #include "base/command_line.h"
+#include "base/lazy_instance.h"
 #include "base/message_loop.h"
 #include "base/process.h"
 #include "base/process_util.h"
 #include "base/strings/string_util.h"
+#include "base/threading/thread_local.h"
 #include "base/tracked_objects.h"
 #include "components/tracing/child_trace_message_filter.h"
 #include "content/child/child_histogram_message_filter.h"
 #include "content/child/child_process.h"
 #include "content/child/child_resource_message_filter.h"
 #include "content/child/fileapi/file_system_dispatcher.h"
 #include "content/child/quota_dispatcher.h"
 #include "content/child/resource_dispatcher.h"
 #include "content/child/socket_stream_dispatcher.h"
 #include "content/child/thread_safe_sender.h"
@@ skipping 10 matching lines @@
 #endif
 
 using tracked_objects::ThreadData;
 
 namespace content {
 namespace {
 
 // How long to wait for a connection to the browser process before giving up.
 const int kConnectionTimeoutS = 15;
 
+base::LazyInstance<base::ThreadLocalPointer<ChildThread> > g_lazy_tls =
+    LAZY_INSTANCE_INITIALIZER;
+
 // This isn't needed on Windows because there the sandbox's job object
 // terminates child processes automatically. For unsandboxed processes (i.e.
 // plugins), PluginThread has EnsureTerminateMessageFilter.
 #if defined(OS_POSIX)
 
 class SuicideOnChannelErrorFilter : public IPC::ChannelProxy::MessageFilter {
  public:
   // IPC::ChannelProxy::MessageFilter
   virtual void OnChannelError() OVERRIDE {
     // For renderer/worker processes:
@@ skipping 20 matching lines @@
     else
       _exit(0);
   }
 
  protected:
   virtual ~SuicideOnChannelErrorFilter() {}
 };
 
 #endif  // OS(POSIX)
 
+#if defined(OS_ANDROID)
+ChildThread* g_child_thread;

[Feng Qian, 2013/06/28 17:12:14]

@jam, won't this be a race condition when both Render and GpuThread are child
threads on Android?

[jam, 2013/07/01 19:29:26]

this is only called by content/app/android/child_process_service.cc, it's my
understanding that this is code which only runs in the multi-process path. am i
mistaken?

+
+void QuitMainThreadMessageLoop() {
+  base::MessageLoop::current()->Quit();
+}
+
+#endif
+
 }  // namespace
 
 ChildThread::ChildThread()
     : channel_connected_factory_(this) {
   channel_name_ = CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
       switches::kProcessChannelID);
   Init();
 }
 
 ChildThread::ChildThread(const std::string& channel_name)
     : channel_name_(channel_name),
       channel_connected_factory_(this) {
   Init();
 }
 
 void ChildThread::Init() {
+  g_lazy_tls.Pointer()->Set(this);
   on_channel_error_called_ = false;
   message_loop_ = base::MessageLoop::current();
   channel_.reset(
       new IPC::SyncChannel(channel_name_,
                            IPC::Channel::MODE_CLIENT,
                            this,
                            ChildProcess::current()->io_message_loop_proxy(),
                            true,
                            ChildProcess::current()->GetShutDownEvent()));
 #ifdef IPC_MESSAGE_LOG_ENABLED
@@ skipping 24 matching lines @@
   // and single-process mode.
   if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kProcessType))
     channel_->AddFilter(new SuicideOnChannelErrorFilter());
 #endif
 
   base::MessageLoop::current()->PostDelayedTask(
       FROM_HERE,
       base::Bind(&ChildThread::EnsureConnected,
                  channel_connected_factory_.GetWeakPtr()),
       base::TimeDelta::FromSeconds(kConnectionTimeoutS));
+
+#if defined(OS_ANDROID)
+  g_child_thread = this;
+#endif
 }
 
 ChildThread::~ChildThread() {
 #ifdef IPC_MESSAGE_LOG_ENABLED
   IPC::Logging::GetInstance()->SetIPCSender(NULL);
 #endif
 
   channel_->RemoveFilter(histogram_message_filter_.get());
   channel_->RemoveFilter(sync_message_filter_.get());
 
   // The ChannelProxy object caches a pointer to the IPC thread, so need to
   // reset it as it's not guaranteed to outlive this object.
   // NOTE: this also has the side-effect of not closing the main IPC channel to
   // the browser process.  This is needed because this is the signal that the
   // browser uses to know that this process has died, so we need it to be alive
   // until this process is shut down, and the OS closes the handle
   // automatically.  We used to watch the object handle on Windows to do this,
   // but it wasn't possible to do so on POSIX.
   channel_->ClearIPCTaskRunner();
+  g_lazy_tls.Pointer()->Set(NULL);
 }
 
 void ChildThread::OnChannelConnected(int32 peer_pid) {
   channel_connected_factory_.InvalidateWeakPtrs();
 }
 
 void ChildThread::OnChannelError() {
   set_on_channel_error_called(true);
   base::MessageLoop::current()->Quit();
 }
@@ skipping 149 matching lines @@
 void ChildThread::OnGetTcmallocStats() {
   std::string result;
   char buffer[1024 * 32];
   base::allocator::GetStats(buffer, sizeof(buffer));
   result.append(buffer);
   Send(new ChildProcessHostMsg_TcmallocStats(result));
 }
 #endif
 
 ChildThread* ChildThread::current() {
-  return ChildProcess::current() ?
-      ChildProcess::current()->main_thread() : NULL;
+  return g_lazy_tls.Pointer()->Get();
 }
 
-bool ChildThread::IsWebFrameValid(WebKit::WebFrame* frame) {
-  // Return false so that it is overridden in any process in which it is used.
-  return false;
+#if defined(OS_ANDROID)
+void ChildThread::ShutdownThread() {
+  DCHECK_NE(base::MessageLoop::current(), g_child_thread->message_loop());
+  g_child_thread->message_loop()->PostTask(
+      FROM_HERE, base::Bind(&QuitMainThreadMessageLoop));
 }
 
+#endif
+
 void ChildThread::OnProcessFinalRelease() {
   if (on_channel_error_called_) {
     base::MessageLoop::current()->Quit();
     return;
   }
 
   // The child process shutdown sequence is a request response based mechanism,
   // where we send out an initial feeler request to the child process host
   // instance in the browser to verify if it's ok to shutdown the child process.
   // The browser then sends back a response if it's ok to shutdown. This avoids
   // race conditions if the process refcount is 0 but there's an IPC message
   // inflight that would addref it.
   Send(new ChildProcessHostMsg_ShutdownRequest);
 }
 
 void ChildThread::EnsureConnected() {
   LOG(INFO) << "ChildThread::EnsureConnected()";
   base::KillProcess(base::GetCurrentProcessHandle(), 0, false);
 }
 
 }  // namespace content