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Fix silent startup deadlock on Windows 11 due to premature FreeLibrary - #1155
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sabrogden merged 2 commits intoSep 22, 2026
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In CPowerManager::Start, powrprof.dll was loaded, PowerRegisterSuspendResumeNotification was called, and ::FreeLibrary(powrprof) was immediately invoked. On modern Windows 11 builds, calling FreeLibrary on powrprof.dll while a suspend/resume notification callback is active causes powrprof to invoke UMPDC.dll, which executes WaitForSingleObjectEx during DLL unload under the loader lock, deadlocking the main UI thread synchronously during CMainFrame::OnCreate. As a result, Ditto hangs permanently on startup without creating its systray icon or showing any windows. In addition, PowerUnregisterSuspendResumeNotification takes HPOWERNOTIFY by value, not by pointer. This fix: 1. Retains HMODULE m_hPowrProf as a member of CPowerManager across the application lifetime. 2. Keeps powrprof.dll loaded while notifications are registered. 3. Corrects the function signature and invocation for PowerUnregisterSuspendResumeNotification. 4. Safely unregisters notifications and frees powrprof.dll only during CPowerManager::Close().
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Copilot review overview
🟡 Changes recommended
Unregister failures are ignored, allowing the module to be unloaded while notifications may remain registered.
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Review effort: Lite
Findings: 1
What changed in this PR
Fixes a Windows startup deadlock by retaining powrprof.dll while power notifications are registered and correcting notification cleanup.
Changes:
- Retains the DLL handle across the manager lifecycle.
- Corrects notification unregistration usage.
- Defers unregistering and unloading until shutdown.
| File | Description |
|---|---|
src/PowerManager.h |
Adds persistent power-management DLL state and updates cleanup declarations. |
src/PowerManager.cpp |
Updates DLL loading, notification registration, unregistration, and cleanup. |
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| PowerUnregisterSuspendResumeNotification(m_registrationHandle); | ||
| } | ||
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| ::FreeLibrary(powrprof); | ||
| m_registrationHandle = 0; | ||
| } | ||
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| ::FreeLibrary(m_hPowrProf); |
sabrogden
approved these changes
Sep 22, 2026
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In CPowerManager::Start, powrprof.dll was loaded, PowerRegisterSuspendResumeNotification was called, and ::FreeLibrary(powrprof) was immediately invoked.
On modern Windows 11 builds, calling FreeLibrary on powrprof.dll while a suspend/resume notification callback is active causes powrprof to invoke UMPDC.dll, which executes WaitForSingleObjectEx during DLL unload under the loader lock, deadlocking the main UI thread synchronously during CMainFrame::OnCreate. As a result, Ditto hangs permanently on startup without creating its systray icon or showing any windows.
In addition, PowerUnregisterSuspendResumeNotification takes HPOWERNOTIFY by value, not by pointer.
This fix:
Windows 11 Pro for Workstations Insider Preview
Dev 29634.1000