1// Copyright (c) 2010 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 CHROME_BROWSER_HANG_MONITOR_HUNG_WINDOW_DETECTOR_H__
6#define CHROME_BROWSER_HANG_MONITOR_HUNG_WINDOW_DETECTOR_H__
7#pragma once
8
9#include "base/synchronization/lock.h"
10#include "chrome/common/worker_thread_ticker.h"
11
12// This class provides the following functionality:
13// Given a top-level window handle, it enumerates all descendant windows
14// of that window and, on finding a window that belongs to a different
15// thread from that of the top-level window, it tests to see if that window
16// is responding to messages. It does this test by first calling the
17// IsHungAppWindow API and, additionally (since the IsHungAppWindow API
18// does not deal correctly with suspended threads), send a dummy message
19// (WM_NULL) to the window and verifies that the call does not timeout.
20// This class is typically used in conjunction with the WorkerThreadTicker
21// class so that the checking can happen on a periodic basis.
22// If a hung window is detected it calls back the specified implementation of
23// the HungWindowNotification interface. Currently this class only supports
24// a single callback but it can be extended later to support multiple
25// callbacks.
26class HungWindowDetector : public WorkerThreadTicker::Callback {
27 public:
28  // This property specifies the message timeout for a child window.
29  static const wchar_t kHungChildWindowTimeout[];
30  // This is the notification callback interface that is used to notify
31  // callers about a non-responsive window
32  class HungWindowNotification  {
33   public:
34    enum ActionOnHungWindow {
35      HUNG_WINDOW_IGNORE,
36      HUNG_WINDOW_TERMINATE_THREAD,
37      HUNG_WINDOW_TERMINATE_PROCESS,
38    };
39
40    // This callback method is invoked when a hung window is detected.
41    // A return value of false indicates that we should stop enumerating the
42    // child windows of the browser window to check if they are hung.
43    virtual bool OnHungWindowDetected(HWND hung_window, HWND top_level_window,
44                                      ActionOnHungWindow* action) = 0;
45  };
46
47  // The notification object is not owned by this class. It is assumed that
48  // this pointer will be valid throughout the lifetime of this class.
49  // Ownership of this pointer is not transferred to this class.
50  // Note that the Initialize method needs to be called to initiate monitoring
51  // of hung windows.
52  explicit HungWindowDetector(HungWindowNotification* notification);
53  ~HungWindowDetector();
54
55  // This method initialized the monitoring of hung windows. All descendant
56  // windows of the passed-in top-level window which belong to a thread
57  // different from that of the top-level window are monitored. The
58  // message_response_timeout parameter indicates how long this class must
59  // wait for a window to respond to a sent message before it is considered
60  // to be non-responsive.
61  // Initialize can be called multiple times to change the actual window to
62  // be monitored as well as the message response timeout
63  bool Initialize(HWND top_level_window,
64                  int message_response_timeout);
65
66  // Implementation of the WorkerThreadTicker::Callback interface
67  virtual void OnTick();
68
69 private:
70  // Helper function that checks whether the specified child window is hung.
71  // If so, it invokes the HungWindowNotification interface implementation
72  bool CheckChildWindow(HWND child_window);
73
74  static BOOL CALLBACK ChildWndEnumProc(HWND child_window, LPARAM param);
75
76  // Pointer to the HungWindowNotification callback interface. This class does
77  // not RefCount this pointer and it is assumed that the pointer will be valid
78  // throughout the lifetime of this class.
79  HungWindowNotification* notification_;
80  HWND top_level_window_;
81
82  // How long do we wait before we consider a window hung (in ms)
83  int message_response_timeout_;
84  base::Lock hang_detection_lock_;
85  // Indicates if this object is currently enumerating hung windows
86  bool enumerating_;
87
88  DISALLOW_COPY_AND_ASSIGN(HungWindowDetector);
89};
90
91
92#endif  // CHROME_BROWSER_HANG_MONITOR_HUNG_WINDOW_DETECTOR_H__
93