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      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.
     26 class 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