LLDB: calling SBProcess::Kill() and SBProcess::ReadMemory() at the same time from two threads hang the debugger

[xusheng6]

If two threads call SBProcess::Kill() and SBProcess::ReadMemory() at the same time, then the LLDB debugger hangs. Which will likely hang BN as well.

This can be triggered in several ways, first, as in #384, the string search thread is constantly reading the debugger memory, and trying to kill the target will cause the hang. Second, since a memory read can happen almost anytime during analysis, it is also very likely to happen when the debugger seems idle. Third, this can happen when the UI thread is updating the xref, leading to a BN hang directly.

This is likely an LLDB bug as well, because its API is said to be thread-safe, i.e., it should be fine to make concurrent calls from two threads since it internally uses lock to protect concurrent access.

Related to #384, #389

[xusheng6]

For the third case, here is the stack trace of the related threads:

1. main thread (updating xref)
   __psynch_mutexwait 0x00000001a9e2da9c
   _pthread_mutex_firstfit_lock_wait 0x00000001a9e67144
   _pthread_mutex_firstfit_lock_slow 0x00000001a9e64a9c
   std::__1::recursive_mutex::lock() 0x00000001a9db9b7c
   0x0000000116989504
   BNGetVariableType 0x00000001169a0f5c
   0x00000001073b8650
   CrossReferenceTreeModel::data(QModelIndex const&, int) const 0x000000010733d410
   QSortFilterProxyModel::data(QModelIndex const&, int) const 0x0000000106c05f10
   CrossReferenceFilterProxyModel::data(QModelIndex const&, int) const 0x000000010734e3bc
   CrossReferenceItemDelegate::paintTreeRow(QPainter*, QStyleOptionViewItem const&, QModelIndex const&) const 0x0000000107348dc4
   QTreeView::drawRow(QPainter*, QStyleOptionViewItem const&, QModelIndex const&) const 0x00000001079bdac4
   QTreeView::drawTree(QPainter*, QRegion const&) const 0x00000001079bbd98
   QTreeView::paintEvent(QPaintEvent*) 0x00000001079bbb68
   QWidget::event(QEvent*) 0x000000010772d620
   QFrame::event(QEvent*) 0x00000001077b07a0
   QAbstractItemView::viewportEvent(QEvent*) 0x000000010794d6f0
   QTreeView::viewportEvent(QEvent*) 0x00000001079bb844
   QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject*, QEvent*) 0x00000001069e2284
   QApplicationPrivate::notify_helper(QObject*, QEvent*) 0x00000001076e4970
   QApplication::notify(QObject*, QEvent*) 0x00000001076e6450
   QCoreApplication::notifyInternal2(QObject*, QEvent*) 0x00000001069e1fb0
   QWidgetPrivate::drawWidget(QPaintDevice*, QRegion const&, QPoint const&, QFlagsQWidgetPrivate::DrawWidgetFlag, QPainter*, QWidgetRepaintManager*) 0x00000001077210a8
   QWidgetRepaintManager::paintAndFlush() 0x000000010773ddf8
   QWidgetRepaintManager::sync() 0x000000010773e190
   QWidget::event(QEvent*) 0x000000010772dac0
   QMainWindow::event(QEvent*) 0x00000001078408f0
   QApplicationPrivate::notify_helper(QObject*, QEvent*) 0x00000001076e4990
   QApplication::notify(QObject*, QEvent*) 0x00000001076e6450
   QCoreApplication::notifyInternal2(QObject*, QEvent*) 0x00000001069e1fb0
   QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) 0x00000001069e32c4
   QCocoaEventDispatcherPrivate::processPostedEvents() 0x000000010a2aff38
   QCocoaEventDispatcherPrivate::postedEventsSourceCallback(void*) 0x000000010a2b05b4
   CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION 0x00000001a9f49a34
   __CFRunLoopDoSource0 0x00000001a9f499c8
   __CFRunLoopDoSources0 0x00000001a9f49738
   __CFRunLoopRun 0x00000001a9f4833c
   CFRunLoopRunSpecific 0x00000001a9f478a4
   RunCurrentEventLoopInMode 0x00000001b35bb3bc
   ReceiveNextEventCommon 0x00000001b35bb200
   _BlockUntilNextEventMatchingListInModeWithFilter 0x00000001b35baf48
   _DPSNextEvent 0x00000001ad1a0630
   -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] 0x00000001ad19f7c0
   -[NSApplication run] 0x00000001ad193bf0
   QCocoaEventDispatcher::processEvents(QFlagsQEventLoop::ProcessEventsFlag) 0x000000010a2af3c4
   QEventLoop::exec(QFlagsQEventLoop::ProcessEventsFlag) 0x00000001069eb3d0
   QCoreApplication::exec() 0x00000001069e264c
   0x0000000104dcfbb0
   start 0x00000001a9b3fe50

2. the thread that is calling Quit
   __ulock_wait 0x00000001a9e2cba4
   _pthread_join 0x00000001a9e6c394
   lldb_private::HostThreadPosix::Join(void**) 0x000000015ec005f4
   lldb_private::Process::ControlPrivateStateThread(unsigned int) 0x000000015ecaa530
   lldb_private::Process::DestroyImpl(bool) 0x000000015ec9f840
   lldb::SBProcess::Kill() 0x000000015eac38c8
   BinaryNinjaDebugger::LldbAdapter::Quit() lldbadapter.cpp:362
   BinaryNinjaDebugger::DebuggerController::ExecuteAdapterAndWait(BNDebuggerAdapterOperation) debuggercontroller.cpp:1629
   BinaryNinjaDebugger::DebuggerController::QuitAndWait() debuggercontroller.cpp:806
   BinaryNinjaDebugger::DebuggerController::Restart() debuggercontroller.cpp:684
   BNDebuggerRestart(BNDebuggerController *) ffi.cpp:369
   BinaryNinjaDebuggerAPI::DebuggerController::Restart() debuggercontroller.cpp:263
   $_12::operator()() const controlswidget.cpp:144
   std::__invoke<…>($_12 &&) type_traits:3918
   std::__thread_execute<…>(std::tuple<…> &, std::__tuple_indices<…>) thread:287
   std::__thread_proxy<…>(void *) thread:298
   _pthread_start 0x00000001a9e6a06c

3. the thread that is calling ReadMemory
   __psynch_mutexwait 0x00000001a9e2da9c
   _pthread_mutex_firstfit_lock_wait 0x00000001a9e67144
   _pthread_mutex_firstfit_lock_slow 0x00000001a9e64a9c
   std::__1::recursive_mutex::lock() 0x00000001a9db9b7c
   lldb::SBProcess::ReadMemory(unsigned long long, void*, unsigned long, lldb::SBError&) 0x000000015eac5368
   BinaryNinjaDebugger::LldbAdapter::ReadMemory(unsigned long, unsigned long) lldbadapter.cpp:676
   BinaryNinjaDebugger::DebuggerMemory::ReadMemory(unsigned long long, unsigned long) debuggerstate.cpp:608
   BinaryNinjaDebugger::DebuggerController::ReadMemory(unsigned long, unsigned long) debuggercontroller.cpp:1180
   BinaryNinjaDebugger::DebugProcessMemoryView::PerformRead(void *, unsigned long long, unsigned long) processview.cpp:164
   BinaryNinja::BinaryView::ReadCallback(void *, void *, unsigned long long, unsigned long) binaryview.cpp:1027
   0x00000001166b1ab4
   0x00000001166b1844
   0x00000001166b1b38
   0x0000000116943f18
   0x000000011695e28c
   0x00000001169ee988
   0x0000000116e96488
   0x0000000116f75e30
   0x0000000116f7567c
   _pthread_start 0x00000001a9e6a06c