root/chrome/browser/hang_monitor/hung_window_detector.cc

DEFINITIONS

1. enumerating_
2. Initialize
3. OnTick
4. CheckChildWindow
5. ChildWndEnumProc

// 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 "chrome/browser/hang_monitor/hung_window_detector.h"

#include <windows.h>
#include <atlbase.h>

#include "base/logging.h"
#include "chrome/browser/hang_monitor/hang_crash_dump_win.h"
#include "content/public/common/result_codes.h"

namespace {

// How long do we wait for the terminated thread or process to die (in ms)
static const int kTerminateTimeout = 2000;

}  // namespace

const wchar_t HungWindowDetector::kHungChildWindowTimeout[] =
    L"Chrome_HungChildWindowTimeout";

HungWindowDetector::HungWindowDetector(HungWindowNotification* notification)
    : notification_(notification),
      top_level_window_(NULL),
      message_response_timeout_(0),
      enumerating_(false) {
  DCHECK(NULL != notification_);
}
// NOTE: It is the caller's responsibility to make sure that
// callbacks on this object have been stopped before
// destroying this object
HungWindowDetector::~HungWindowDetector() {
}

bool HungWindowDetector::Initialize(HWND top_level_window,
                                    int message_response_timeout) {
  if (NULL ==  notification_) {
    return false;
  }
  if (NULL == top_level_window) {
    return false;
  }
  // It is OK to call Initialize on this object repeatedly
  // with different top lebel HWNDs and timeout values each time.
  // And we do not need a lock for this because we are just
  // swapping DWORDs.
  top_level_window_ = top_level_window;
  message_response_timeout_ = message_response_timeout;
  return true;
}

void HungWindowDetector::OnTick() {
  do {
    base::AutoLock lock(hang_detection_lock_);
    // If we already are checking for hung windows on another thread,
    // don't do this again.
    if (enumerating_) {
      return;
    }
    enumerating_ = true;
  } while (false);  // To scope the AutoLock

  EnumChildWindows(top_level_window_, ChildWndEnumProc,
                   reinterpret_cast<LPARAM>(this));

  // The window shouldn't be disabled unless we're showing a modal dialog.
  // If we're not, then reenable the window.
  if (!::IsWindowEnabled(top_level_window_) &&
      !::GetWindow(top_level_window_, GW_ENABLEDPOPUP)) {
    ::EnableWindow(top_level_window_, TRUE);
  }

  enumerating_ = false;
}

bool HungWindowDetector::CheckChildWindow(HWND child_window) {
  // It can happen that the window is DOA. It specifically happens
  // when we have just killed a plugin process and the enum is still
  // enumerating windows from that process.
  if (!IsWindow(child_window))  {
    return true;
  }

  DWORD top_level_window_thread_id =
      GetWindowThreadProcessId(top_level_window_, NULL);

  DWORD child_window_process_id = 0;
  DWORD child_window_thread_id =
      GetWindowThreadProcessId(child_window, &child_window_process_id);
  bool continue_hang_detection = true;

  if (top_level_window_thread_id != child_window_thread_id) {
    // The message timeout for a child window starts of with a default
    // value specified by the message_response_timeout_ member. It is
    // tracked by a property on the child window.
#pragma warning(disable:4311)
    int child_window_message_timeout =
        reinterpret_cast<int>(GetProp(child_window, kHungChildWindowTimeout));
#pragma warning(default:4311)
    if (!child_window_message_timeout) {
      child_window_message_timeout = message_response_timeout_;
    }

    DWORD_PTR result = 0;
    if (0 == SendMessageTimeout(child_window,
                                WM_NULL,
                                0,
                                0,
                                SMTO_BLOCK,
                                child_window_message_timeout,
                                &result)) {
      HungWindowNotification::ActionOnHungWindow action =
          HungWindowNotification::HUNG_WINDOW_IGNORE;
#pragma warning(disable:4312)
      SetProp(child_window, kHungChildWindowTimeout,
              reinterpret_cast<HANDLE>(child_window_message_timeout));
#pragma warning(default:4312)
      continue_hang_detection =
        notification_->OnHungWindowDetected(child_window, top_level_window_,
                                            &action);
      // Make sure this window still a child of our top-level parent
      if (!IsChild(top_level_window_, child_window)) {
        return continue_hang_detection;
      }

      if (action == HungWindowNotification::HUNG_WINDOW_TERMINATE_PROCESS) {
        RemoveProp(child_window, kHungChildWindowTimeout);
        CHandle child_process(OpenProcess(PROCESS_ALL_ACCESS,
                                          FALSE,
                                          child_window_process_id));

        if (NULL == child_process.m_h) {
          return continue_hang_detection;
        }
        // Before swinging the axe, do some sanity checks to make
        // sure this window still belongs to the same process
        DWORD process_id_check = 0;
        GetWindowThreadProcessId(child_window, &process_id_check);
        if (process_id_check !=  child_window_process_id) {
          return continue_hang_detection;
        }

        // Before terminating the process we try collecting a dump. Which
        // a transient thread in the child process will do for us.
        CrashDumpAndTerminateHungChildProcess(child_process);
        child_process.Close();
      }
    } else {
      RemoveProp(child_window, kHungChildWindowTimeout);
    }
  }

  return continue_hang_detection;
}

BOOL CALLBACK HungWindowDetector::ChildWndEnumProc(HWND child_window,
                                                   LPARAM param) {
  HungWindowDetector* detector_instance =
      reinterpret_cast<HungWindowDetector*>(param);
  if (NULL == detector_instance) {
    NOTREACHED();
    return FALSE;
  }

  return detector_instance->CheckChildWindow(child_window);
}