content/child/child_process.h

   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 #ifndef CONTENT_CHILD_CHILD_PROCESS_H_
   6 #define CONTENT_CHILD_CHILD_PROCESS_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/memory/scoped_ptr.h"
  10 #include "base/synchronization/waitable_event.h"
  11 #include "base/threading/thread.h"
  12 #include "content/common/content_export.h"
  13
  14 namespace content {
  15 class ChildThreadImpl;
  16
  17 // Base class for child processes of the browser process (i.e. renderer and
  18 // plugin host). This is a singleton object for each child process.
  19 //
  20 // During process shutdown the following sequence of actions happens in
  21 // order.
  22 //
  23 // 1. ChildProcess::~ChildProcess() is called.
  24 //   2. Shutdown event is fired. Background threads should stop.
  25 //   3. ChildThreadImpl::Shutdown() is called. ChildThread is also deleted.
  26 //   4. IO thread is stopped.
  27 // 5. Main message loop exits.
  28 // 6. Child process is now fully stopped.
  29 //
  30 // Note: IO thread outlives the ChildThreadImpl object.
  31 class CONTENT_EXPORT ChildProcess {
  32  public:
  33   // Child processes should have an object that derives from this class.
  34   // Normally you would immediately call set_main_thread after construction.
  35   ChildProcess();
  36   virtual ~ChildProcess();
  37
  38   // May be NULL if the main thread hasn't been set explicitly.
  39   ChildThreadImpl* main_thread();
  40
  41   // Sets the object associated with the main thread of this process.
  42   // Takes ownership of the pointer.
  43   void set_main_thread(ChildThreadImpl* thread);
  44
  45   base::MessageLoop* io_message_loop() { return io_thread_.message_loop(); }
  46   base::SingleThreadTaskRunner* io_task_runner() {
  47     return io_thread_.task_runner().get();
  48   }
  49
  50   // A global event object that is signalled when the main thread's message
  51   // loop exits.  This gives background threads a way to observe the main
  52   // thread shutting down.  This can be useful when a background thread is
  53   // waiting for some information from the browser process.  If the browser
  54   // process goes away prematurely, the background thread can at least notice
  55   // the child processes's main thread exiting to determine that it should give
  56   // up waiting.
  57   // For example, see the renderer code used to implement GetCookies().
  58   base::WaitableEvent* GetShutDownEvent();
  59
  60   // These are used for ref-counting the child process.  The process shuts
  61   // itself down when the ref count reaches 0.
  62   // For example, in the renderer process, generally each tab managed by this
  63   // process will hold a reference to the process, and release when closed.
  64   void AddRefProcess();
  65   void ReleaseProcess();
  66
  67   // Getter for the one ChildProcess object for this process. Can only be called
  68   // on the main thread.
  69   static ChildProcess* current();
  70
  71   static void WaitForDebugger(const std::string& label);
  72  private:
  73   int ref_count_;
  74
  75   // An event that will be signalled when we shutdown.
  76   base::WaitableEvent shutdown_event_;
  77
  78   // The thread that handles IO events.
  79   base::Thread io_thread_;
  80
  81   // NOTE: make sure that main_thread_ is listed after shutdown_event_, since
  82   // it depends on it (indirectly through IPC::SyncChannel).  Same for
  83   // io_thread_.
  84   scoped_ptr<ChildThreadImpl> main_thread_;
  85
  86   DISALLOW_COPY_AND_ASSIGN(ChildProcess);
  87 };
  88
  89 }  // namespace content
  90
  91 #endif  // CONTENT_CHILD_CHILD_PROCESS_H_