SalInstance::DoYield: Don't drop SolarMutex when accessing user event queue

<https://ci.libreoffice.org/job/lo_tb_master_linux_dbg/14468/console> fails with
the assert in the OSL_DEBUG_LEVEL > 0 test code in
Scheduler::ProcessEventsToIdle firing (see below), indicating that (even though
the SolarMutex is locked one frame up in VCLXToolkit::processEventsToIdle), when
Application::Reschedule(true) returned, there are unprocessed events in the
queue.

That failure is with the headless plugin, and looking at
SvpSalInstance::DoYield, there was a window of time after m_aEventGuard has been
released and before the SolarMutex has been re-acquired, where other threads
could enqueue events.

If Application::Reschedule(true) can thus not guarantee that the queue is empty
when it returned, that would mean that the assert in
Scheduler::ProcessEventsToIdle (introduced with
c0710abfebd320903a3edb23d4b1441ea351b0be "Add some Scheduler unit tests and
logging") is bogus.

However, at least the two SalInstance::DoYield implementations
SvpSalInstance::DoYield and AquaSalInstance::DoYield appear to have no reason
in the first place to drop the SolarMutex when accessing the user event queue.
So removing that dropping should make the assert in
Scheduler::ProcessEventsToIdle faithful, at least for these two implementations.

But I have no idea whether the other three implementations
(X11SalInstance::DoYield in vcl/unx/generic/app/salinst.cxx,
GtkInstance::DoYield in vcl/unx/gtk/gtkinst.cxx, and WinSalInstance::DoYield in
vcl/win/app/salinst.cxx) have similar issues---i.e., whether everything is good
after this change, whether those other implementations need similar changes, or
whether ultimately Application::Reschedule(true) cannot guarantee the queue to
be empty upon return (in which case the assert in Scheduler::ProcessEventsToIdle
would need to go).

> warn:vcl.schedule:27575:54:vcl/source/app/svapp.cxx:535: Unprocessed Idle: vcl::Window maPaintIdle
> soffice.bin: /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/vcl/source/app/svapp.cxx:540: static void Scheduler::ProcessEventsToIdle(): Assertion `!bAnyIdle' failed.
[...]
> Thread 2 (Thread 0x2b12bf1e4a00 (LWP 27575)):
> #0  0x00002b12bfb1a69d in poll () at /lib64/libc.so.6
> #1  0x00002b12ca9129e7 in SvpSalInstance::DoReleaseYield(int) (this=0x1be8b40, nTimeoutMS=5) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/vcl/headless/svpinst.cxx:392
>         aPoll = {fd = 6, events = 1, revents = 0}
>         nAcquireCount = 1
> #2  0x00002b12ca9128c9 in SvpSalInstance::DoYield(bool, bool, unsigned long) (this=0x1be8b40, bWait=true, bHandleAllCurrentEvents=false, nReleased=0) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/vcl/headless/svpinst.cxx:375
>         nTimeoutMS = 5
>         __PRETTY_FUNCTION__ = "virtual bool SvpSalInstance::DoYield(bool, bool, sal_uLong)"
>         aEvents = empty std::__debug::list
>         nAcquireCount = 1
>         bEvent = false
> #3  0x00002b12ca7a98cd in ImplYield(bool, bool, unsigned long) (i_bWait=true, i_bAllEvents=false, nReleased=0) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/vcl/source/app/svapp.cxx:484
>         pSVData = 0x2b12cb2a9e00 <rtl::Static<ImplSVData, (anonymous namespace)::private_aImplSVData>::get()::instance>
>         bProcessedEvent = false
> #4  0x00002b12ca7a5796 in Application::Yield() () at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/vcl/source/app/svapp.cxx:555
> #5  0x00002b12ca7a52f5 in Application::Execute() () at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/vcl/source/app/svapp.cxx:461
>         pSVData = 0x2b12cb2a9e00 <rtl::Static<ImplSVData, (anonymous namespace)::private_aImplSVData>::get()::instance>
> #6  0x00002b12bf69c7e5 in desktop::Desktop::DoExecute() () at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/desktop/source/app/app.cxx:1350
> #7  0x00002b12bf69d9c4 in desktop::Desktop::Main() (this=0x7fff49ea9ac0) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/desktop/source/app/app.cxx:1735
>         layer2 = {m_aEnvTypeName = "gcc3", m_xPreviousContext = uno::Reference to (desktop::DesktopContext *) 0x1bebdf8}
>         rCmdLineArgs = @0x2b12bfa2c6a0: {m_cwdUrl = boost::optional "file:///home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/workdir/JunitTest/sd_unoapi/user", m_minimized = false, m_invisible = false, m_norestore = true, m_headless = true, m_eventtesting = false, m_quickstart = false, m_noquickstart = true, m_terminateafterinit = false, m_nologo = true, m_nolockcheck = false, m_nodefault = false, m_help = false, m_writer = false, m_calc = false, m_draw = false, m_impress = false, m_global = false, m_math = false, m_web = false, m_base = false, m_helpwriter = false, m_helpcalc = false, m_helpdraw = false, m_helpbasic = false, m_helpmath = false, m_helpimpress = false, m_helpbase = false, m_version = false, m_splashpipe = false, m_textcat = false, m_scriptcat = false, m_safemode = false, m_unknown = "", m_bEmpty = false, m_bDocumentArgs = false, m_accept = std::__debug::vector of length 1, capacity 1 = {"pipe,name=oootest16264f8c-0bcc-4a4f-9c1b-52af72b78eb5;urp"}, m_unaccept = std::__debug::vector of length 0, capacity 0, m_openlist = std::__debug::vector of length 0, capacity 0, m_viewlist = std::__debug::vector of length 0, capacity 0, m_startlist = std::__debug::vector of length 0, capacity 0, m_forceopenlist = std::__debug::vector of length 0, capacity 0, m_forcenewlist = std::__debug::vector of length 0, capacity 0, m_printlist = std::__debug::vector of length 0, capacity 0, m_printtolist = std::__debug::vector of length 0, capacity 0, m_printername = "", m_conversionlist = std::__debug::vector of length 0, capacity 0, m_conversionparams = "", m_conversionout = "", m_infilter = std::__debug::vector of length 0, capacity 0, m_language = "", m_pidfile = ""}
>         xRestartManager = uno::Reference to (comphelper::OOfficeRestartManager *) 0x29a7bf8
>         layer = {m_aEnvTypeName = "gcc3", m_xPreviousContext = uno::Reference to (DesktopEnvironmentContext *) 0x1bebc38}
>         xContext = uno::Reference to (cppu::ComponentContext *) 0x1d200b0
>         aOptions = {<utl::detail::Options> = {<utl::ConfigurationBroadcaster> = {_vptr.ConfigurationBroadcaster = 0x2b12c8a3dfb0 <vtable for SvtAccessibilityOptions+16>, mpList = std::unique_ptr<std::__debug::vector<utl::ConfigurationListener*, std::allocator<utl::ConfigurationListener*> >> containing 0x0, m_nBroadcastBlocked = 0, m_nBlockedHint = NONE}, <utl::ConfigurationListener> = {_vptr.ConfigurationListener = 0x2b12c8a3dfe8 <vtable for SvtAccessibilityOptions+72>}, <No data fields>}, <SfxListener> = {_vptr.SfxListener = 0x2b12c8a3e010 <vtable for SvtAccessibilityOptions+112>, mpImpl = std::unique_ptr<SfxListener::Impl> containing 0x2a46530}, static sm_pSingleImplConfig = 0x2a47e60, static sm_nAccessibilityRefCount = 16}
>         eStatus = desktop::Desktop::BS_OK
>         aUnknown = ""
>         inst_fin = desktop::userinstall::EXISTED
>         xDesktop = uno::Reference to (framework::Desktop *) 0x29cb3a8
>         aAppearanceCfg = {<utl::ConfigItem> = {<utl::ConfigurationBroadcaster> = {_vptr.ConfigurationBroadcaster = 0x2b12c8a3e090 <vtable for SvtTabAppearanceCfg+16>, mpList = std::unique_ptr<std::__debug::vector<utl::ConfigurationListener*, std::allocator<utl::ConfigurationListener*> >> containing 0x0, m_nBroadcastBlocked = 0, m_nBlockedHint = NONE}, sSubTree = "Office.Common/View", m_xHierarchyAccess = uno::Reference to (configmgr::RootAccess *) 0x29ca3f8, xChangeLstnr = empty uno::Reference, m_nMode = DelayedUpdate, m_bIsModified = false, m_bEnableInternalNotification = false, m_nInValueChange = 0}, nDragMode = SystemDep, nSnapMode = NONE, nMiddleMouse = (unknown: 2), nAAMinPixelHeight = 8, bMenuMouseFollow = true, bFontAntialiasing = true, static bInitialized = true}
> #8  0x00002b12ca7b33d0 in ImplSVMain() () at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/vcl/source/app/svmain.cxx:194
>         pSVData = 0x2b12cb2a9e00 <rtl::Static<ImplSVData, (anonymous namespace)::private_aImplSVData>::get()::instance>
>         nReturn = 1
>         bInit = true
> #9  0x00002b12ca7b3539 in SVMain() () at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/vcl/source/app/svmain.cxx:232
>         nRet = 0
> #10 0x00002b12bf6f1ff1 in soffice_main() () at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/desktop/source/app/sofficemain.cxx:163
>         bSuccess = true
>         aDesktop = {<Application> = {_vptr.Application = 0x2b12bfa269b0 <vtable for desktop::Desktop+16>}, m_rSplashScreen = empty uno::Reference, m_bCleanedExtensionCache = false, m_bServicesRegistered = true, m_aBootstrapError = desktop::Desktop::BE_OK, m_aBootstrapErrorMessage = "", m_aBootstrapStatus = desktop::Desktop::BS_OK, m_xLockfile = std::unique_ptr<desktop::Lockfile> containing 0x29c9b10, m_firstRunTimer = {<Task> = {_vptr.Task = 0x2b12cb2911b0 <vtable for Timer+16>, mpSchedulerData = 0x0, mpDebugName = 0x2b12bf777570 "desktop::Desktop m_firstRunTimer", mePriority = DEFAULT, mbActive = false}, maInvokeHandler = {function_ = 0x2b12bf6a2c6c <desktop::Desktop::LinkStubAsyncInitFirstRun(void*, Timer*)>, instance_ = 0x7fff49ea9ac0}, mnTimeout = 3000, mbAuto = false}, m_aUpdateThread = {_M_id = {_M_thread = 0}}, static pResMgr = 0x0}
>         rCmdLineArgs = @0x2b12bfa2c6a0: {m_cwdUrl = boost::optional "file:///home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/workdir/JunitTest/sd_unoapi/user", m_minimized = false, m_invisible = false, m_norestore = true, m_headless = true, m_eventtesting = false, m_quickstart = false, m_noquickstart = true, m_terminateafterinit = false, m_nologo = true, m_nolockcheck = false, m_nodefault = false, m_help = false, m_writer = false, m_calc = false, m_draw = false, m_impress = false, m_global = false, m_math = false, m_web = false, m_base = false, m_helpwriter = false, m_helpcalc = false, m_helpdraw = false, m_helpbasic = false, m_helpmath = false, m_helpimpress = false, m_helpbase = false, m_version = false, m_splashpipe = false, m_textcat = false, m_scriptcat = false, m_safemode = false, m_unknown = "", m_bEmpty = false, m_bDocumentArgs = false, m_accept = std::__debug::vector of length 1, capacity 1 = {"pipe,name=oootest16264f8c-0bcc-4a4f-9c1b-52af72b78eb5;urp"}, m_unaccept = std::__debug::vector of length 0, capacity 0, m_openlist = std::__debug::vector of length 0, capacity 0, m_viewlist = std::__debug::vector of length 0, capacity 0, m_startlist = std::__debug::vector of length 0, capacity 0, m_forceopenlist = std::__debug::vector of length 0, capacity 0, m_forcenewlist = std::__debug::vector of length 0, capacity 0, m_printlist = std::__debug::vector of length 0, capacity 0, m_printtolist = std::__debug::vector of length 0, capacity 0, m_printername = "", m_conversionlist = std::__debug::vector of length 0, capacity 0, m_conversionparams = "", m_conversionout = "", m_infilter = std::__debug::vector of length 0, capacity 0, m_language = "", m_pidfile = ""}
>         aUnknown = ""
> #11 0x0000000000400957 in sal_main () at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/desktop/source/app/main.c:48
>         ret = 0
> #12 0x000000000040093d in main (argc=8, argv=0x7fff49ea9df8) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/desktop/source/app/main.c:47
>         ret = 0
>
> Thread 1 (Thread 0x2b12e6862700 (LWP 11663)):
> #0  0x00002b12bfa635f7 in raise () at /lib64/libc.so.6
> #1  0x00002b12bfa64ce8 in abort () at /lib64/libc.so.6
> #2  0x00002b12bf406165 in (anonymous namespace)::callSystemHandler(int, siginfo_t*, void*) (signal=6, info=0x2b12e68607f0, context=0x2b12e68606c0) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/sal/osl/unx/signal.cxx:389
>         act = {__sigaction_handler = {sa_handler = 0x0, sa_sigaction = 0x0}, sa_mask = {__val = {0 <repeats 16 times>}}, sa_flags = 0, sa_restorer = 0xe6860b90}
>         i = 5
> #3  0x00002b12bf406472 in (anonymous namespace)::signalHandlerFunction(int, siginfo_t*, void*) (signal=6, info=0x2b12e68607f0, context=0x2b12e68606c0) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/sal/osl/unx/signal.cxx:486
>         act = {__sigaction_handler = {sa_handler = 0x2b12e68607e0, sa_sigaction = 0x2b12e68607e0}, sa_mask = {__val = {0, 18446744069414584320, 0, 0, 61329184, 47360176948768, 47356309405696, 0, 47356309405696, 47356309405696, 4294967295, 47356309405696, 0, 0, 47359528444352, 47360176950400}}, sa_flags = -72537977, sa_restorer = 0x2b12bfdea1c0 <_IO_2_1_stderr_>}
>         Info = {Signal = osl_Signal_AccessViolation, UserSignal = 6, UserData = 0x0}
> #4  0x00002b12bfa63670 in <signal handler called> () at /lib64/libc.so.6
> #5  0x00002b12bfa635f7 in raise () at /lib64/libc.so.6
> #6  0x00002b12bfa64ce8 in abort () at /lib64/libc.so.6
> #7  0x00002b12bfa5c566 in __assert_fail_base () at /lib64/libc.so.6
> #8  0x00002b12bfa5c612 in  () at /lib64/libc.so.6
> #9  0x00002b12ca7a56ba in Scheduler::ProcessEventsToIdle() () at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/vcl/source/app/svapp.cxx:540
>         pSVData = 0x2b12cb2a9e00 <rtl::Static<ImplSVData, (anonymous namespace)::private_aImplSVData>::get()::instance>
>         bAnyIdle = true
>         __PRETTY_FUNCTION__ = "static void Scheduler::ProcessEventsToIdle()"
>         nSanity = 1
>         pSchedulerData = 0x0
> #10 0x00002b12c8c8c554 in (anonymous namespace)::VCLXToolkit::processEventsToIdle() (this=0x3abc2a0) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/toolkit/source/awt/vclxtoolkit.cxx:1897
>         aSolarGuard = {m_solarMutex = @0x1be9610}
>         aZone = {m_sProfileId = 0x2b12c8e672a2 "processEvents", m_aCreateTime = 0}
> #11 0x00002b12e317751d in gcc3::callVirtualMethod(void*, unsigned int, void*, _typelib_TypeDescriptionReference*, bool, unsigned long*, unsigned int, unsigned long*, double*) (pThis=0x3abc2f0, nVtableIndex=9, pRegisterReturn=0x0, pReturnTypeRef=0x1c07390, bSimpleReturn=true, pStack=0x2b12e6861170, nStack=0, pGPR=0x2b12e68612d0, pFPR=0x2b12e6861300) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/bridges/source/cpp_uno/gcc3_linux_x86-64/callvirtualmethod.cxx:133
>         data = {pMethod = 47359678006708, pStack = 0x2b12e6861170, nStack = 0, pGPR = 0x2b12e68612d0, pFPR = 0x2b12e6861300, rax = 0, rdx = 47360176951616, xmm0 = 2.3399007939816937e-310, xmm1 = 3.0079874608688941e-316}
>         pMethod = 47359683834264
> #12 0x00002b12e317615c in cpp_call(bridges::cpp_uno::shared::UnoInterfaceProxy*, bridges::cpp_uno::shared::VtableSlot, typelib_TypeDescriptionReference*, sal_Int32, typelib_MethodParameter*, void*, void**, uno_Any**) (pThis=0x3ab9a80, aVtableSlot=..., pReturnTypeRef=0x1c07390, nParams=0, pParams=0x0, pUnoReturn=0x0, pUnoArgs=0x0, ppUnoExc=0x2b12e6861488) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/bridges/source/cpp_uno/gcc3_linux_x86-64/uno2cpp.cxx:237
>         pStack = 0x2b12e6861170
>         pFPR = {2.3399036413000935e-310, 2.3399017635979741e-310, 1.9097962118687451e-313, 2.3399036413020203e-310, 2.9003052604790195e-316, -1.3614915359519845e+193, 2.339903641302465e-310, 0}
>         __PRETTY_FUNCTION__ = "void cpp_call(bridges::cpp_uno::shared::UnoInterfaceProxy*, bridges::cpp_uno::shared::VtableSlot, typelib_TypeDescriptionReference*, sal_Int32, typelib_MethodParameter*, void*, void**, uno_Any**)"
>         pCppArgs = 0x2b12e6861160
>         pStackStart = 0x2b12e6861170
>         pGPR = {61588208, 9, 47360176952128, 47360119419570, 0, 58702832}
>         nTempIndices = 0
>         nFPR = 0
>         pAdjustedThisPtr = 0x3abc2f0
>         ppTempParamTypeDescr = 0x2b12e6861160
>         nGPR = 1
>         pReturnTypeDescr = 0x1c07390
>         pCppReturn = 0x0
>         bSimpleReturn = true
>         pTempIndices = 0x2b12e6861160
> #13 0x00002b12e3176bdb in bridges::cpp_uno::shared::unoInterfaceProxyDispatch(_uno_Interface*, _typelib_TypeDescription const*, void*, void**, _uno_Any**) (pUnoI=0x3ab9a80, pMemberDescr=0x37fbbf0, pReturn=0x0, pArgs=0x0, ppException=0x2b12e6861488) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/bridges/source/cpp_uno/gcc3_linux_x86-64/uno2cpp.cxx:425
>         nMemberPos = 27
>         aVtableSlot = {offset = 0, index = 9}
>         pThis = 0x3ab9a80
>         pTypeDescr = 0x2b14740
>         __PRETTY_FUNCTION__ = "void bridges::cpp_uno::shared::unoInterfaceProxyDispatch(uno_Interface*, const typelib_TypeDescription*, void*, void**, uno_Any**)"
> #14 0x00002b12e441cf28 in binaryurp::IncomingRequest::execute_throw(binaryurp::BinaryAny*, std::__debug::vector<binaryurp::BinaryAny, std::allocator<binaryurp::BinaryAny> >*) const (this=0x3a0fd50, returnValue=0x2b12e68618a0, outArguments=0x2b12e6861920) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/binaryurp/source/incomingrequest.cxx:242
>         exc = <error reading variable: Cannot access memory at address 0x7261686320747376>
>         pexc = 0x2b12e68614b0
>         retType = {_pTypeDescr = 0x1c07390}
>         nSize = 0
>         retBuf = std::__debug::vector of length 0, capacity 0
>         outBufs = empty std::__debug::list
>         args = std::__debug::vector of length 0, capacity 0
>         __PRETTY_FUNCTION__ = "bool binaryurp::IncomingRequest::execute_throw(binaryurp::BinaryAny*, std::__debug::vector<binaryurp::BinaryAny>*) const"
>         isExc = false
> #15 0x00002b12e441bd16 in binaryurp::IncomingRequest::execute() const (this=0x3a0fd50) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/binaryurp/source/incomingrequest.cxx:79
>         resetCc = true
>         oldCc = {m_pUnoI = 0x0}
>         ret = {data_ = _uno_Any(void)}
>         outArgs = std::__debug::vector of length 0, capacity 0
>         isExc = false
> #16 0x00002b12e443c7a4 in binaryurp::(anonymous namespace)::request(void*) (pThreadSpecificData=0x3a0fd50) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/binaryurp/source/reader.cxx:85
>         __PRETTY_FUNCTION__ = "void binaryurp::{anonymous}::request(void*)"
> #17 0x00002b12c2ce1f5f in cppu_threadpool::JobQueue::enter(long, bool) (this=0x3ab9da0, nDisposeId=61386512, bReturnWhenNoJob=true) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/cppu/source/threadpool/jobqueue.cxx:107
>         guard = {pT = 0x3ab9da0}
>         job = {pThreadSpecificData = 0x3a0fd50, doRequest = 0x2b12e443c73b <binaryurp::(anonymous namespace)::request(void*)>}
>         pReturn = 0x0
> #18 0x00002b12c2ce6bfd in cppu_threadpool::ORequestThread::run() (this=0x3a8af10) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/cppu/source/threadpool/thread.cxx:172
> #19 0x00002b12c2ce712b in osl::threadFunc(void*) (param=0x3a8af20) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/include/osl/thread.hxx:185
>         pObj = 0x3a8af20
> #20 0x00002b12bf40d7bd in osl_thread_start_Impl(void*) (pData=0x3a4c7e0) at /home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/sal/osl/unx/thread.cxx:237
>         terminate = false
>         pImpl = 0x3a4c7e0
>         __PRETTY_FUNCTION__ = "void* osl_thread_start_Impl(void*)"
> #21 0x00002b12bfdf7dc5 in start_thread () at /lib64/libpthread.so.0
> #22 0x00002b12bfb24ced in clone () at /lib64/libc.so.6
[...]
> make[1]: *** [/home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/workdir/JunitTest/sd_unoapi/done] Error 1

Change-Id: I7d034c02a49d315104d8329a4e1119e14e8e5e40
Reviewed-on: https://gerrit.libreoffice.org/40176
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>

2 files changed, 0 insertions, 7 deletions

diff --git a/vcl/headless/svpinst.cxx b/vcl/headless/svpinst.cxx
index 5140b27340b3..4b76f0c3fbec 100644
--- a/vcl/headless/svpinst.cxx
+++ b/vcl/headless/svpinst.cxx
@@ -310,9 +310,7 @@ bool SvpSalInstance::DoYield(bool bWait, bool bHandleAllCurrentEvents, sal_uLong
     assert(nReleased == 0); // not implemented
     // first, check for already queued events.
 
-    // release yield mutex
     std::list< SalUserEvent > aEvents;
-    sal_uLong nAcquireCount = ReleaseYieldMutex();
     {
         osl::MutexGuard g(m_aEventGuard);
         if( ! m_aUserEvents.empty() )
@@ -329,8 +327,6 @@ bool SvpSalInstance::DoYield(bool bWait, bool bHandleAllCurrentEvents, sal_uLong
             }
         }
     }
-    // acquire yield mutex again
-    AcquireYieldMutex( nAcquireCount );
 
     bool bEvent = !aEvents.empty();
     if( bEvent )
diff --git a/vcl/osx/salinst.cxx b/vcl/osx/salinst.cxx
index f06504cc9678..4f98d64cdb76 100644
--- a/vcl/osx/salinst.cxx
+++ b/vcl/osx/salinst.cxx
@@ -556,8 +556,6 @@ bool AquaSalInstance::DoYield(bool bWait, bool bHandleAllCurrentEvents, sal_uLon
     bool bDispatchUser = true;
     while( bDispatchUser )
     {
-        sal_uLong nCount = ReleaseYieldMutex();
-
         // get one user event
         SalUserEvent aEvent( nullptr, nullptr, SalEvent::NONE );
         {
@@ -571,7 +569,6 @@ bool AquaSalInstance::DoYield(bool bWait, bool bHandleAllCurrentEvents, sal_uLon
             else
                 bDispatchUser = false;
         }
-        AcquireYieldMutex( nCount );
 
         // dispatch it
         if( aEvent.mpFrame && AquaSalFrame::isAlive( aEvent.mpFrame ) )