WinForms关闭时WM_SETTINGCHANGE引发OnUserPreferenceChanging挂起的非延迟解决方案咨询

在一款关闭时会修改桌面布局的Windows Forms应用中，Windows Forms处理WM_SETTINGCHANGE消息时出现挂起，该问题会在应用关闭流程期间收到任何WM_SETTINGCHANGE消息时触发。除了添加任意延迟外，是否存在其他方法可以避免此挂起？

事件时间线 #

1. 主线程关闭唯一窗体时，触发桌面布局修改（具体通过SHAppBarMessage(ABM_REMOVE, ...)移除AppBar）
2. 主线程开始关闭流程，释放控件、窗体等资源
3. ".NET System Events"线程收到WM_SETTINGCHANGE消息，尝试调用主线程执行处理逻辑
4. 由于主线程尚未完全关闭，WindowsFormsSynchronizationContext.Send:82处的检测通过，允许跨线程调用
5. ".NET System Events"线程进入WaitHandle等待状态，等待主线程执行完成
6. 主线程在主窗体关闭后退出消息循环，Main方法返回
7. 应用陷入挂起状态

挂起时调用栈 #

主线程（仅原生栈，无.NET栈） #

win32u.dll!NtUserMsgWaitForMultipleObjectsEx()
combase.dll!CCliModalLoop::BlockFn(void * * ahEvent, unsigned long cEvents, unsigned long * lpdwSignaled) Line 2108
combase.dll!ClassicSTAThreadWaitForHandles(unsigned long dwFlags, unsigned long dwTimeout, unsigned long cHandles, void * * pHandles, unsigned long * pdwIndex) Line 54
combase.dll!CoWaitForMultipleHandles(unsigned long dwFlags, unsigned long dwTimeout, unsigned long cHandles, void * * pHandles, unsigned long * pdwindex) Line 126
[Inline Frame] hostpolicy.dll!coreclr_t::shutdown(int *) Line 152
hostpolicy.dll!run_app_for_context(const hostpolicy_context_t & context, int argc, const wchar_t * * argv) Line 264
...snip...

.NET System Events线程 #

System.Private.CoreLib.dll!System.Threading.WaitHandle.WaitOneNoCheck(int millisecondsTimeout) Line 139
    at /_/src/libraries/System.Private.CoreLib/src/System/Threading/WaitHandle.cs(139)
System.Windows.Forms.dll!System.Windows.Forms.Control.WaitForWaitHandle(System.Threading.WaitHandle waitHandle) Line 3967
    at /_/src/System.Windows.Forms/src/System/Windows/Forms/Control.cs(3967)
System.Windows.Forms.dll!System.Windows.Forms.Control.MarshaledInvoke(System.Windows.Forms.Control caller, System.Delegate method, object[] args, bool synchronous) Line 7141
    at /_/src/System.Windows.Forms/src/System/Windows/Forms/Control.cs(7141)
System.Windows.Forms.dll!System.Windows.Forms.Control.Invoke(System.Delegate method, object[] args) Line 6587
    at /_/src/System.Windows.Forms/src/System/Windows/Forms/Control.cs(6587)
System.Windows.Forms.dll!System.Windows.Forms.WindowsFormsSynchronizationContext.Send(System.Threading.SendOrPostCallback d, object state) Line 88
    at /_/src/System.Windows.Forms/src/System/Windows/Forms/WindowsFormsSynchronizationContext.cs(88)
Microsoft.Win32.SystemEvents.dll!Microsoft.Win32.SystemEvents.SystemEventInvokeInfo.Invoke(bool checkFinalization, object[] args) Line 35
    at Microsoft.Win32\SystemEvents.cs(35)
Microsoft.Win32.SystemEvents.dll!Microsoft.Win32.SystemEvents.RaiseEvent(bool checkFinalization, object key, object[] args) Line 850
    at Microsoft.Win32\SystemEvents.cs(850)
    locals:
        array[0] 
            ._delegate = System.Windows.Forms.VisualStyles.VisualStyleRenderer.OnUserPreferenceChanging
            ._syncCtx = System.Windows.Forms.WindowsFormsSynchronizationContext
Microsoft.Win32.SystemEvents.dll!Microsoft.Win32.SystemEvents.WindowProc(nint hWnd, int msg, nint wParam, nint lParam) Line 961
    at Microsoft.Win32\SystemEvents.cs(961)
    locals:
        msg = 8218
        wParam = 0x2f
        lParam = 0
[Native to Managed Transition]
[Managed to Native Transition]
Microsoft.Win32.SystemEvents.dll!Interop.User32.DispatchMessageW.____PInvoke|210_0(Interop.User32.MSG* msg)
Microsoft.Win32.SystemEvents.dll!Microsoft.Win32.SystemEvents.WindowThreadProc() Line 1038
    at Microsoft.Win32\SystemEvents.cs(1038)

关键注意事项 #

• 未在后台线程创建控件，因此常规的跨线程控件创建挂起排查方案不适用
• 该问题属于已知的WinForms系统事件挂起场景，已有相关讨论案例
• 已向.NET WinForms官方提交Issue：关闭期间收到WM_SETTINGCHANGE时出现挂起
• 复现条件：窗体上至少包含一个控件（通过VisualStyleRenderer..cctor触发SystemEvents.UserPreferenceChanging事件注册）
• 复现代码分为两类：基于SHAppBarMessage的真实场景复现，以及基于SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE, ...)的极简复现，同时提供了内存转储文件用于分析

内容的提问来源于stack exchange，提问作者Mitch