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POWindows hang in WM_WINDOWPOSCHANGED
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copied!<p>I have a DirectX9 application that sporadically runs into a hang in WM_WINDOWPOSCHANGED. The hang occurs only rarely when alt+tabbing into and out of fullscreen exclusive mode.</p> <p>The application is hung because the main window message processing thread is stuck at WaitForSingleObject() in the DefWindowProc handler. Other threads we have created are operating normally.</p> <p>Call Stack on Stuck Main Thread:</p> <pre><code> ntdll.dll!_NtWaitForSingleObject@12() + 0x15 bytes ntdll.dll!_NtWaitForSingleObject@12() + 0x15 bytes kernel32.dll!_WaitForSingleObjectExImplementation@12() + 0x43 bytes kernel32.dll!_WaitForSingleObject@8() + 0x12 bytes d3d9.dll!WindowProc() + 0x27e95 bytes user32.dll!_InternalCallWinProc@20() + 0x23 bytes user32.dll!_UserCallWinProcCheckWow@32() + 0xb7 bytes user32.dll!_DispatchClientMessage@24() + 0x51 bytes user32.dll!___fnDWORD@4() + 0x2b bytes ntdll.dll!_KiUserCallbackDispatcher@12() + 0x2e bytes user32.dll!_NtUserMessageCall@28() + 0x15 bytes user32.dll!_RealDefWindowProcWorker@24() + 0x26afe bytes user32.dll!_RealDefWindowProcW@16() + 0x2a bytes uxtheme.dll!_ThemeDefWindowProc() + 0x152 bytes uxtheme.dll!_ThemeDefWindowProcW@16() + 0x18 bytes user32.dll!_DefWindowProcW@16() + 0x805 bytes > Player.exe!cnWindowProc(HWND__ * hWnd=0x006507f4, unsigned int message=0x00000047, unsigned int wParam=0x00000000, long lParam=0x0034eea8) Line 502 + 0x18 bytes C++ </code></pre> <p>I am wondering what Windows is waiting for here. DirectX is created and owned by a separate thread, but that thread is not stuck. We seem to be handling things correctly for lost devices (freeing up video memory resources and calling Reset()). </p> <p>If anyone has ideas on why windows is hanging here, I would appreciate it.</p>

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