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  1. JDK
  2. JDK-4068651

Win32: Deadlock while hiding a Dialog

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    Details

    • Subcomponent:
    • Resolved In Build:
      1.1.4
    • CPU:
      x86
    • OS:
      windows_nt
    • Verification:
      Not verified

      Description

      Bug Description from Christopher Harrison (Oracle) email:

      ===========================================================
      We have run in to a deadlock caused by Javasoft's fix for bug #4048664.
      Here is a descriptionof the problem, in case you haven't seen this yet:

      AWT-Window Thread AWT-EventQueue Thread
      ----------------- ---------------------
                                               calls WDialogPeer.hide()
                                                 calls AwtDialog::EndModal()
                                                   enters critical section
      receives a WM_AWT_COMPONENT_SHOW
        calls ShowWindow()
          receives a WM_KILLFOCUS for Dialog
            calls SendFocusEvent()
              blocks to enter critical section
                                                     posts WM_AWT_QUEUE_SYNC to the
                                                     Window Thread and waits for it
                                                     to be processed


      I have stopped this deadlock from occurring by removing the critical
      section from ~AwtDialog and reducing the scope of the critical section
      in AwtDialog::EndModal() as shown below. Exiting the critical section
      before waiting for the AWT-Window Thread to process WM_AWT_QUEUE_SYNC
      prevents the deadlock.

      I am not sure whether this fix is thread safe however. Is it safe to
      leave this critical section before executing the rest of this function?
      If not the bug fix for #4048664 will have to be modified.


      AwtDialog::~AwtDialog() {
          // Oracle Bug #515756: Critical section is entered in EndModal
      --> // CriticalSection::Lock l(GetLock());
          if (m_modalWnd != NULL) {
              EndModal();
          }
          if (m_disabledWnds != NULL) {
              delete[] m_disabledWnds;
          }
      }

      void AwtDialog::EndModal()
      {
          if (AwtToolkit::GetInstance().GetModalDialog() != this) { // Fix for bug #4045610 -
      Oracle problem with
                                                                       // "deadlocking" (more accurately, failing to
                                                                       // re-enable the modal dialog's parent...)
                                                                       // when closing nested dialogs (out of order).
              return;
          }
          if ((GetStyle() & WS_VISIBLE) == 0) {
              return;
          }

      // Oracle Bug #515756: Release critical section after posting messages, so that we
      // don't deadlock waiting for the Window Thread.
      --> {
      --> CriticalSection::Lock l(GetLock());

      AwtToolkit::GetInstance().ResetModal(m_previousModalDialog);
      Hide();

      // Enable all previously disabled windows.
      if (m_disabledWnds != NULL) {
      for (int i = 0; i < m_nWnds; i++) {
      // Post "enable" messages, since this object is locked. This is necessary because one
      // of them may yank focus from this object, causing a FocusEvent to be fired -- posting
      // that event requires this component's lock.
      ::PostMessage(m_disabledWnds[i], WM_AWT_COMPONENT_ENABLE, TRUE, 0);
      }
      delete[] m_disabledWnds;
      m_disabledWnds = NULL;
      m_nWnds = 0;
      }
      ---> }

          // Bug #4048664 (Hide does not work on modal dialog)
          // Wait for all posted messages to be processed
          HANDLE hevt = CreateEvent(NULL, TRUE, FALSE, NULL);
          ASSERT(hevt);
          ::PostMessage(GetHWnd(), WM_AWT_QUEUE_SYNC, (WPARAM)hevt, 0);
          WaitForSingleObject(hevt, INFINITE);
          CloseHandle(hevt);

          if (m_onMainThread) {
              AwtToolkit::GetInstance().StopMessagePump();
          } else {
              Hsun_awt_windows_WDialogPeer* peer = GetPeer();
              monitorEnter(obj_monitor(peer));
              monitorNotifyAll(obj_monitor(peer));
              monitorExit(obj_monitor(peer));
          }

          if (m_previousModalDialog != NULL) {
              ::SetForegroundWindow(m_previousModalDialog->GetHWnd());
              m_previousModalDialog = NULL;
          } else {
              AwtComponent* parent = GetParent();
              if (parent != NULL) {
                  ::SetForegroundWindow(parent->GetHWnd());
              }
          }

          // Bug #4048664 (Hide does not work on modal dialog)
          m_modalWnd = NULL;
          ::SetProp(GetHWnd(), "hidden", (HANDLE)1);
      }
       
       

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            Assignee:
            tballsunw Tom Ball (Inactive)
            Reporter:
            tyao Ting-Yun Ingrid Yao (Inactive)
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              Updated:
              Resolved:
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