Prevent deadlock in DeInitVCL() on Windows

Seen in local make check build:

1. A unit test is being finished, calling DeInitVCL() in main thread, which
holds solar mutex; it is now attempting to dispose clipboard listener,
which needs to lock CWinClipbImpl::s_aMutex:

=====
sysdtrans.dll!osl::Guard<osl::Mutex>::Guard<osl::Mutex>(osl::Mutex & t) Line 136
at C:\lo\src\core\include\osl\mutex.hxx(136)
sysdtrans.dll!CWinClipbImpl::~CWinClipbImpl() Line 67
at C:\lo\src\core\dtrans\source\win32\clipb\WinClipbImpl.cxx(67)
sysdtrans.dll!CWinClipbImpl::`scalar deleting destructor'(unsigned int)
sysdtrans.dll!std::default_delete<CWinClipbImpl>::operator()(CWinClipbImpl * _Ptr) Line 1765
at C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.24.28314\include\memory(1765)
sysdtrans.dll!std::unique_ptr<CWinClipbImpl,std::default_delete<CWinClipbImpl>>::reset(CWinClipbImpl * _Ptr) Line 1908
at C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.24.28314\include\memory(1908)
sysdtrans.dll!CWinClipboard::disposing() Line 220
at C:\lo\src\core\dtrans\source\win32\clipb\WinClipboard.cxx(220)
cppuhelper3MSC.dll!cppu::WeakComponentImplHelperBase::dispose() Line 102
at C:\lo\src\core\cppuhelper\source\implbase.cxx(102)
sysdtrans.dll!cppu::PartialWeakComponentImplHelper<com::sun::star::datatransfer::clipboard::XSystemClipboard,com::sun::star::datatransfer::clipboard::XFlushableClipboard,com::sun::star::lang::XServiceInfo>::dispose() Line 90
at C:\lo\src\core\include\cppuhelper\compbase.hxx(90)
vcllo.dll!DeInitVCL() Line 492
at C:\lo\src\core\vcl\source\app\svmain.cxx(492)
vclbootstrapprotector.dll!`anonymous namespace'::Protector::~Protector() Line 32
at C:\lo\src\core\test\source\vclbootstrapprotector.cxx(32)
vclbootstrapprotector.dll!`anonymous namespace'::Protector::`scalar deleting destructor'(unsigned int)
cppunitd_dll.dll!CppUnit::ProtectorChain::pop() Line 56
at C:\lo\src\build\workdir\UnpackedTarball\cppunit\src\cppunit\ProtectorChain.cpp(56)
cppunitd_dll.dll!CppUnit::TestResult::popProtector() Line 197
at C:\lo\src\build\workdir\UnpackedTarball\cppunit\src\cppunit\TestResult.cpp(197)
cppunittester.exe!`anonymous namespace'::ProtectedFixtureFunctor::run() Line 325
at C:\lo\src\core\sal\cppunittester\cppunittester.cxx(325)
cppunittester.exe!sal_main() Line 466
at C:\lo\src\core\sal\cppunittester\cppunittester.cxx(466)
cppunittester.exe!main(int argc, char * * argv) Line 373
at C:\lo\src\core\sal\cppunittester\cppunittester.cxx(373)
=====

2. Simultaneously, clipboard listener thread calls onClipboardContentChanged,
which has locked CWinClipbImpl::s_aMutex, and now it's trying to post user
event in SfxClipboardChangeListener::changedContents, which needs to lock
solar mutex in ImplGetDefaultContextWindow:

=====
comphelper.dll!comphelper::SolarMutex::acquire(unsigned long nLockCount) Line 87
at C:\lo\src\core\include\comphelper\solarmutex.hxx(87)
vcllo.dll!osl::Guard<comphelper::SolarMutex>::Guard<comphelper::SolarMutex>(comphelper::SolarMutex & t) Line 136
at C:\lo\src\core\include\osl\mutex.hxx(136)
vcllo.dll!SolarMutexGuard::SolarMutexGuard() Line 1343
at C:\lo\src\core\include\vcl\svapp.hxx(1343)
vcllo.dll!ImplGetDefaultContextWindow() Line 227
at C:\lo\src\core\vcl\source\app\svdata.cxx(227)
vcllo.dll!ImplGetDefaultWindow() Line 217
at C:\lo\src\core\vcl\source\app\svdata.cxx(217)
vcllo.dll!Application::PostUserEvent(const Link<void *,void> & rLink, void * pCaller, bool bReferenceLink) Line 1000
at C:\lo\src\core\vcl\source\app\svapp.cxx(1000)
sfxlo.dll!SfxClipboardChangeListener::changedContents(const com::sun::star::datatransfer::clipboard::ClipboardEvent & __formal) Line 215
at C:\lo\src\core\sfx2\source\view\viewsh.cxx(215)
sysdtrans.dll!CWinClipboard::notifyAllClipboardListener() Line 189
at C:\lo\src\core\dtrans\source\win32\clipb\WinClipboard.cxx(189)
sysdtrans.dll!CWinClipbImpl::onClipboardContentChanged() Line 179
at C:\lo\src\core\dtrans\source\win32\clipb\WinClipbImpl.cxx(179)
sysdtrans.dll!CMtaOleClipboard::clipboardChangedNotifierThreadProc(void * pParam) Line 705
at C:\lo\src\core\dtrans\source\win32\clipb\MtaOleClipb.cxx(705)
ucrtbased.dll!thread_start<unsigned int (__cdecl*)(void *),1>(void * const parameter) Line 97
at minkernel\crts\ucrt\src\appcrt\startup\thread.cpp(97)
kernel32.dll!BaseThreadInitThunk()
ntdll.dll!RtlUserThreadStart()
=====

=> the two threads deadlock waiting for mutexes locked in each other.

Resolve it by using SolarMutexReleaser around the call disposing the clipboard
listener in DeInitVCL. An alternative could be using solar mutex instead of
CWinClipbImpl::s_aMutex.

Change-Id: Ifd76ce5a7d969a568539602eae2139b4ef0c5858
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/87318
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/vcl/source/app/svmain.cxx b/vcl/source/app/svmain.cxx
index bfa5279ca4ca..998ece19dc21 100644
--- a/vcl/source/app/svmain.cxx
+++ b/vcl/source/app/svmain.cxx
@@ -489,7 +489,8 @@ void DeInitVCL()
     if (auto const comp = css::uno::Reference<css::lang::XComponent>(
             pSVData->m_xSystemClipboard, css::uno::UNO_QUERY))
     {
-        comp->dispose();
+        SolarMutexReleaser r; // unblock pending "clipboard content changed" notifications
+        comp->dispose(); // will use CWinClipbImpl::s_aMutex
     }
 #endif