src/mojo/shell/app_child_process.cc

   1 // Copyright 2014 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 "mojo/shell/app_child_process.h"
   6
   7 #include "base/bind.h"
   8 #include "base/callback_helpers.h"
   9 #include "base/files/file_path.h"
  10 #include "base/location.h"
  11 #include "base/logging.h"
  12 #include "base/macros.h"
  13 #include "base/memory/ref_counted.h"
  14 #include "base/memory/scoped_ptr.h"
  15 #include "base/message_loop/message_loop.h"
  16 #include "base/scoped_native_library.h"
  17 #include "base/single_thread_task_runner.h"
  18 #include "base/synchronization/waitable_event.h"
  19 #include "base/threading/thread.h"
  20 #include "base/threading/thread_checker.h"
  21 #include "mojo/common/message_pump_mojo.h"
  22 #include "mojo/embedder/embedder.h"
  23 #include "mojo/embedder/simple_platform_support.h"
  24 #include "mojo/public/cpp/system/core.h"
  25 #include "mojo/shell/app_child_process.mojom.h"
  26
  27 namespace mojo {
  28 namespace shell {
  29
  30 namespace {
  31
  32 // Blocker ---------------------------------------------------------------------
  33
  34 // Blocks a thread until another thread unblocks it, at which point it unblocks
  35 // and runs a closure provided by that thread.
  36 class Blocker {
  37  public:
  38   class Unblocker {
  39    public:
  40     ~Unblocker() {}
  41
  42     void Unblock(base::Closure run_after) {
  43       DCHECK(blocker_);
  44       DCHECK(blocker_->run_after_.is_null());
  45       blocker_->run_after_ = run_after;
  46       blocker_->event_.Signal();
  47       blocker_ = NULL;
  48     }
  49
  50    private:
  51     friend class Blocker;
  52     Unblocker(Blocker* blocker) : blocker_(blocker) {
  53       DCHECK(blocker_);
  54     }
  55
  56     Blocker* blocker_;
  57
  58     // Copy and assign allowed.
  59   };
  60
  61   Blocker() : event_(true, false) {}
  62   ~Blocker() {}
  63
  64   void Block() {
  65     DCHECK(run_after_.is_null());
  66     event_.Wait();
  67     run_after_.Run();
  68   }
  69
  70   Unblocker GetUnblocker() {
  71     return Unblocker(this);
  72   }
  73
  74  private:
  75   base::WaitableEvent event_;
  76   base::Closure run_after_;
  77
  78   DISALLOW_COPY_AND_ASSIGN(Blocker);
  79 };
  80
  81 // AppContext ------------------------------------------------------------------
  82
  83 class AppChildControllerImpl;
  84
  85 static void DestroyController(scoped_ptr<AppChildControllerImpl> controller) {
  86 }
  87
  88 // Should be created and initialized on the main thread.
  89 class AppContext {
  90  public:
  91   AppContext()
  92       : io_thread_("io_thread"),
  93         controller_thread_("controller_thread") {}
  94   ~AppContext() {}
  95
  96   void Init() {
  97     // Initialize Mojo before starting any threads.
  98     embedder::Init(scoped_ptr<mojo::embedder::PlatformSupport>(
  99         new mojo::embedder::SimplePlatformSupport()));
 100
 101     // Create and start our I/O thread.
 102     base::Thread::Options io_thread_options(base::MessageLoop::TYPE_IO, 0);
 103     CHECK(io_thread_.StartWithOptions(io_thread_options));
 104     io_runner_ = io_thread_.message_loop_proxy().get();
 105     CHECK(io_runner_.get());
 106
 107     // Create and start our controller thread.
 108     base::Thread::Options controller_thread_options;
 109     controller_thread_options.message_loop_type =
 110         base::MessageLoop::TYPE_CUSTOM;
 111     controller_thread_options.message_pump_factory =
 112         base::Bind(&common::MessagePumpMojo::Create);
 113     CHECK(controller_thread_.StartWithOptions(controller_thread_options));
 114     controller_runner_ = controller_thread_.message_loop_proxy().get();
 115     CHECK(controller_runner_.get());
 116   }
 117
 118   void Shutdown() {
 119     controller_runner_->PostTask(
 120         FROM_HERE,
 121         base::Bind(&DestroyController, base::Passed(&controller_)));
 122   }
 123
 124   base::SingleThreadTaskRunner* io_runner() const {
 125     return io_runner_.get();
 126   }
 127
 128   base::SingleThreadTaskRunner* controller_runner() const {
 129     return controller_runner_.get();
 130   }
 131
 132   AppChildControllerImpl* controller() const {
 133     return controller_.get();
 134   }
 135
 136   void set_controller(scoped_ptr<AppChildControllerImpl> controller) {
 137     controller_ = controller.Pass();
 138   }
 139
 140  private:
 141   // Accessed only on the controller thread.
 142   // IMPORTANT: This must be BEFORE |controller_thread_|, so that the controller
 143   // thread gets joined (and thus |controller_| reset) before |controller_| is
 144   // destroyed.
 145   scoped_ptr<AppChildControllerImpl> controller_;
 146
 147   base::Thread io_thread_;
 148   scoped_refptr<base::SingleThreadTaskRunner> io_runner_;
 149
 150   base::Thread controller_thread_;
 151   scoped_refptr<base::SingleThreadTaskRunner> controller_runner_;
 152
 153   DISALLOW_COPY_AND_ASSIGN(AppContext);
 154 };
 155
 156 // AppChildControllerImpl ------------------------------------------------------
 157
 158 class AppChildControllerImpl : public InterfaceImpl<AppChildController> {
 159  public:
 160   virtual ~AppChildControllerImpl() {
 161     DCHECK(thread_checker_.CalledOnValidThread());
 162
 163     // TODO(vtl): Pass in the result from |MainMain()|.
 164     client()->AppCompleted(MOJO_RESULT_UNIMPLEMENTED);
 165   }
 166
 167   // To be executed on the controller thread. Creates the |AppChildController|,
 168   // etc.
 169   static void Init(
 170       AppContext* app_context,
 171       embedder::ScopedPlatformHandle platform_channel,
 172       const Blocker::Unblocker& unblocker) {
 173     DCHECK(app_context);
 174     DCHECK(platform_channel.is_valid());
 175
 176     DCHECK(!app_context->controller());
 177
 178     scoped_ptr<AppChildControllerImpl> impl(
 179         new AppChildControllerImpl(app_context, unblocker));
 180
 181     ScopedMessagePipeHandle host_message_pipe(embedder::CreateChannel(
 182         platform_channel.Pass(),
 183         app_context->io_runner(),
 184         base::Bind(&AppChildControllerImpl::DidCreateChannel,
 185                    base::Unretained(impl.get())),
 186         base::MessageLoopProxy::current()));
 187
 188     BindToPipe(impl.get(), host_message_pipe.Pass());
 189
 190     app_context->set_controller(impl.Pass());
 191   }
 192
 193   virtual void OnConnectionError() OVERRIDE {
 194     // TODO(darin): How should we handle a connection error here?
 195   }
 196
 197   // |AppChildController| methods:
 198   virtual void StartApp(const String& app_path,
 199                         ScopedMessagePipeHandle service) OVERRIDE {
 200     DVLOG(2) << "AppChildControllerImpl::StartApp(" << app_path << ", ...)";
 201     DCHECK(thread_checker_.CalledOnValidThread());
 202
 203     unblocker_.Unblock(base::Bind(&AppChildControllerImpl::StartAppOnMainThread,
 204                                   base::FilePath::FromUTF8Unsafe(app_path),
 205                                   base::Passed(&service)));
 206   }
 207
 208  private:
 209   AppChildControllerImpl(AppContext* app_context,
 210                          const Blocker::Unblocker& unblocker)
 211       : app_context_(app_context),
 212         unblocker_(unblocker),
 213         channel_info_(NULL) {
 214   }
 215
 216   // Callback for |embedder::CreateChannel()|.
 217   void DidCreateChannel(embedder::ChannelInfo* channel_info) {
 218     DVLOG(2) << "AppChildControllerImpl::DidCreateChannel()";
 219     DCHECK(thread_checker_.CalledOnValidThread());
 220     channel_info_ = channel_info;
 221   }
 222
 223   static void StartAppOnMainThread(const base::FilePath& app_path,
 224                                    ScopedMessagePipeHandle service) {
 225     // TODO(vtl): This is copied from in_process_dynamic_service_runner.cc.
 226     DVLOG(2) << "Loading/running Mojo app from " << app_path.value()
 227              << " out of process";
 228
 229     do {
 230       base::NativeLibraryLoadError load_error;
 231       base::ScopedNativeLibrary app_library(
 232           base::LoadNativeLibrary(app_path, &load_error));
 233       if (!app_library.is_valid()) {
 234         LOG(ERROR) << "Failed to load library (error: " << load_error.ToString()
 235                    << ")";
 236         break;
 237       }
 238
 239       typedef MojoResult (*MojoMainFunction)(MojoHandle);
 240       MojoMainFunction main_function = reinterpret_cast<MojoMainFunction>(
 241           app_library.GetFunctionPointer("MojoMain"));
 242       if (!main_function) {
 243         LOG(ERROR) << "Entrypoint MojoMain not found";
 244         break;
 245       }
 246
 247       // TODO(vtl): Report the result back to our parent process.
 248       // |MojoMain()| takes ownership of the service handle.
 249       MojoResult result = main_function(service.release().value());
 250       if (result < MOJO_RESULT_OK)
 251         LOG(ERROR) << "MojoMain returned an error: " << result;
 252     } while (false);
 253   }
 254
 255   base::ThreadChecker thread_checker_;
 256   AppContext* const app_context_;
 257   Blocker::Unblocker unblocker_;
 258
 259   embedder::ChannelInfo* channel_info_;
 260
 261   DISALLOW_COPY_AND_ASSIGN(AppChildControllerImpl);
 262 };
 263
 264 }  // namespace
 265
 266 // AppChildProcess -------------------------------------------------------------
 267
 268 AppChildProcess::AppChildProcess() {
 269 }
 270
 271 AppChildProcess::~AppChildProcess() {
 272 }
 273
 274 void AppChildProcess::Main() {
 275   DVLOG(2) << "AppChildProcess::Main()";
 276
 277   AppContext app_context;
 278   app_context.Init();
 279
 280   Blocker blocker;
 281   app_context.controller_runner()->PostTask(
 282       FROM_HERE,
 283       base::Bind(&AppChildControllerImpl::Init, base::Unretained(&app_context),
 284                  base::Passed(platform_channel()), blocker.GetUnblocker()));
 285   // This will block, then run whatever the controller wants.
 286   blocker.Block();
 287
 288   app_context.Shutdown();
 289 }
 290
 291 }  // namespace shell
 292 }  // namespace mojo