[WinCairo] Dead lock in WTF::Thread::didExit() while WebKitNetworkProcess.exe is exiting By running run-webkit-tests, sometimes WebKitNetworkProcess.exe process doesn't exit. > python ./Tools/Scripts/run-webkit-tests --wincairo --debug --no-new-test-results --no-retry-failures --no-show-results -f fast There is only the main thread, and here is its callstack. Callstack: > ntdll.dll!NtWaitForAlertByThreadId() Unknown > ntdll.dll!RtlSleepConditionVariableSRW() Unknown > KernelBase.dll!SleepConditionVariableSRW() Unknown > WTF.dll!WTF::ThreadCondition::timedWait(WTF::Mutex & mutex={...}, WTF::WallTime absoluteTime={...}) Line 383 C++ > WTF.dll!WTF::ParkingLot::parkConditionallyImpl(const void * address=0x00007ffc1ec325ac, const WTF::ScopedLambda<bool __cdecl(void)> & validation={...}, const WTF::ScopedLambda<void __cdecl(void)> & beforeSleep={...}, const WTF::TimeWithDynamicClockType & timeout={...}) Line 604 C++ > WTF.dll!WTF::ParkingLot::parkConditionally<bool <lambda>(void),void <lambda>(void)>(const void * address=0x00007ffc1ec325ac, const WTF::ParkingLot::compareAndPark::__l2::bool <lambda>(void) & validation=bool <lambda>(void){...}, const WTF::ParkingLot::compareAndPark::__l2::void <lambda>(void) & beforeSleep=void <lambda>(void){...}, const WTF::TimeWithDynamicClockType & timeout={...}) Line 82 C++ > WTF.dll!WTF::ParkingLot::compareAndPark<unsigned char,unsigned char>(const WTF::Atomic<unsigned char> * address=0x00007ffc1ec325ac, unsigned char expected='\x3') Line 94 C++ > WTF.dll!WTF::LockAlgorithm<unsigned char,1,2,WTF::EmptyLockHooks<unsigned char>>::lockSlow(WTF::Atomic<unsigned char> & lock={...}) Line 83 C++ > WTF.dll!WTF::Lock::lockSlow() Line 41 C++ > WTF.dll!WTF::Lock::lock() Line 60 C++ > WTF.dll!WTF::Locker<WTF::Lock>::lock() Line 114 C++ > WTF.dll!WTF::Locker<WTF::Lock>::Locker<WTF::Lock>(WTF::Lock & lockable={...}) Line 55 C++ > WTF.dll!WTF::Thread::didExit() Line 226 C++ > WTF.dll!WTF::Thread::ThreadHolder::~ThreadHolder() Line 274 C++ > WTF.dll!WTF::`dynamic atexit destructor for 's_threadHolder''() C++ > WTF.dll!__dyn_tls_dtor(void * __formal=0x000000007ffe0385, const unsigned long dwReason, void * __formal) Line 119 C++ > ntdll.dll!LdrpCallInitRoutine() Unknown > ntdll.dll!LdrpCallTlsInitializers() Unknown > ntdll.dll!LdrShutdownProcess() Unknown > ntdll.dll!RtlExitUserProcess() Unknown > kernel32.dll!ExitProcessImplementation() Unknown > ucrtbase.dll!exit_or_terminate_process() Unknown > ucrtbase.dll!common_exit() Unknown > WebKitNetworkProcess.exe!__scrt_common_main_seh() Line 295 C++ > kernel32.dll!BaseThreadInitThunk() Unknown > ntdll.dll!RtlUserThreadStart() Unknown I don't know when this issue started to happen, but not so long time ago. I fixed very similar issue in 5 months ago. Bug 204192 – [WinCairo] dead lock in Thread::destructTLS