The main problem you are running into is in async mode when you say "launch" or "continue", those calls will return immediately and you must consume the events to make sure it is safe to do things. If your process is stopped, then until your actually resume your process with process.Continue() or any thread.StepXXX() calls, your process will stay stopped. But when you ask to make it run, you must consume events to know what the process is actually doing...
> On Feb 12, 2016, at 10:02 AM, Greg Clayton via lldb-dev > <lldb-dev@lists.llvm.org> wrote: > > If you are going to set async to true, then you must consume the events by > waiting for events. See the following example: > > svn cat > http://llvm.org/svn/llvm-project/lldb/trunk/examples/python/process_events.py > > So you can rewrite your wait_for_process_stop to use the debugger to fetch > the events and do things correctly: > > def wait_for_process_stop(debugger): > event_timeout_in_seconds = 10 > listener = debugger.GetListener() > event = lldb.SBEvent() > stopped = False > while not stopped: > if listener.WaitForEvent (event_timeout_in_seconds, event): > if lldb.SBProcess.EventIsProcessEvent(event): > state = lldb.SBProcess.GetStateFromEvent (event) > if state == lldb.eStateStopped: > // Watch for something that stopped and restarted automatically > if SBProcess::GetRestartedFromEvent(event) == False: > stopped = True > > > The other option is to do it to set Async to False and then your > target.Launch won't return until the process is stopped. Also if you do > "process.Continue()" it won't return until the process is stopped. But you > lose your ability to stop the process if things go wrong... > > Greg > >> On Feb 4, 2016, at 9:09 PM, Jeffrey Tan via lldb-dev >> <lldb-dev@lists.llvm.org> wrote: >> >> After adding some logging I figured out that the race condition is caused by >> process.Continue() did not guarantee process has been really resumed yet in >> async mode, so the second wait_for_process_stop() is skipped immediately to >> kill listener thread and destroying debugger. I know I have a race condition >> bug here because of polling for process state, but why is lldb crashing when >> listener thread has exited and SBDebugger.Destroy() is called? What is the >> situation that SBDebugger.Destroy() can be called safely? >> >> ==================do_test================== >> Launch result: success >> <Listener> Listening Thread ID: 4660334592 >> WaitForEvent... >> Target event: ModulesLoaded >> WaitForEvent... >> Process event: StateChanged, Stopped >> Stop reason: 5 >> WaitForEvent... >> Breakpoint event: [Added] SBBreakpoint: id = 1, name = 'main', locations = 1 >> WaitForEvent... >> [main] killing listener thread >> Process event: StateChanged, Running >> Stop reason: 0 >> <Listener> Exiting listener thread >> [main] destroy debugger >> Segmentation fault: 11 >> >> On Thu, Feb 4, 2016 at 8:22 PM, Jeffrey Tan <jeffrey.fu...@gmail.com> wrote: >> Sorry, I have actually tried to exit the event listening thread before >> debugger destroy, but still go the crash randomly(1 out of 5 runs). Here is >> the code: >> >> >> ==========Main Thread========== >> def wait_for_process_stop(process): >> while not process.is_stopped: >> time.sleep(0.1) >> >> def launch_debugging(debugger, stop_at_entry): >> error = lldb.SBError() >> listener = lldb.SBListener('Chrome Dev Tools Listener') >> target = debugger.GetSelectedTarget() >> process = target.Launch (listener, >> None, # argv >> None, # envp >> None, # stdin_path >> None, # stdout_path >> None, # stderr_path >> None, # working directory >> 0, # launch flags >> stop_at_entry, # Stop at entry >> error) # error >> print 'Launch result: %s' % str(error) >> listener_thread = LLDBListenerThread(debugger) >> listener_thread.start() >> return listener_thread >> >> def do_test(): >> debugger = lldb.SBDebugger.Create() >> debugger.SetAsync(True) >> executable_path = '~/Personal/compiler/CompilerConstruction/code/compiler' >> target = debugger.CreateTargetWithFileAndArch(executable_path, >> lldb.LLDB_ARCH_DEFAULT) >> >> listener_thread = launch_debugging(debugger, stop_at_entry=True) >> process = debugger.GetSelectedTarget().process >> >> wait_for_process_stop(process) # wait for entry breakpoint. >> target.BreakpointCreateByName('main') >> process.Continue() >> wait_for_process_stop(process) # wait for main breakpoint. >> >> listener_thread.should_quit = True >> listener_thread.join() >> >> lldb.SBDebugger.Destroy(debugger) >> >> def main(): >> do_test() >> do_test() >> >> ==========Listening Thread========== >> class LLDBListenerThread(Thread): >> should_quit = False >> >> def __init__(self, debugger): >> Thread.__init__(self) >> process = debugger.GetSelectedTarget().process >> self.listener = debugger.GetListener() >> self._add_listener_to_process(process) >> self._add_listener_to_target(process.target) >> >> def _add_listener_to_target(self, target): >> # Listen for breakpoint/watchpoint events >> (Added/Removed/Disabled/etc). >> broadcaster = target.GetBroadcaster() >> mask = lldb.SBTarget.eBroadcastBitBreakpointChanged | >> lldb.SBTarget.eBroadcastBitWatchpointChanged | >> lldb.SBTarget.eBroadcastBitModulesLoaded >> broadcaster.AddListener(self.listener, mask) >> >> def _add_listener_to_process(self, process): >> # Listen for process events (Start/Stop/Interrupt/etc). >> broadcaster = process.GetBroadcaster() >> mask = lldb.SBProcess.eBroadcastBitStateChanged | >> lldb.SBProcess.eBroadcastBitSTDOUT | lldb.SBProcess.eBroadcastBitSTDERR | >> lldb.SBProcess.eBroadcastBitInterrupt >> broadcaster.AddListener(self.listener, mask) >> >> def run(self): >> while not self.should_quit: >> event = lldb.SBEvent() >> print 'WaitForEvent...' >> if self.listener.WaitForEvent(1, event): >> if lldb.SBTarget.EventIsTargetEvent(event): >> self._handle_target_event(event) >> elif lldb.SBProcess.EventIsProcessEvent(event): >> self._handle_process_event(event) >> elif lldb.SBBreakpoint.EventIsBreakpointEvent(event): >> self._handle_breakpoint_event(event) >> elif lldb.SBThread.EventIsThreadEvent(event): >> self._handle_thread_event(event) >> else: >> self._handle_unknown_event(event) >> >> _hand_XXX_event() methods just dump some logging information of the debug >> events. >> >> >> Crashed Thread: 0 Dispatch queue: com.apple.main-thread >> >> Exception Type: EXC_BAD_ACCESS (SIGSEGV) >> Exception Codes: EXC_I386_GPFLT >> >> Thread 0 Crashed:: Dispatch queue: com.apple.main-thread >> 0 _lldb.so 0x0000000111528179 >> EventMatcher::operator()(std::__1::shared_ptr<lldb_private::Event> const&) >> const + 21 >> 1 _lldb.so 0x00000001115275d2 >> lldb_private::Listener::FindNextEventInternal(lldb_private::Broadcaster*, >> lldb_private::ConstString const*, unsigned int, unsigned int, >> std::__1::shared_ptr<lldb_private::Event>&, bool) + 176 >> 2 _lldb.so 0x0000000111527952 >> lldb_private::Listener::WaitForEventsInternal(lldb_private::TimeValue >> const*, lldb_private::Broadcaster*, lldb_private::ConstString const*, >> unsigned int, unsigned int, std::__1::shared_ptr<lldb_private::Event>&) + 134 >> 3 _lldb.so 0x0000000111527ae9 >> lldb_private::Listener::WaitForEventForBroadcasterWithType(lldb_private::TimeValue >> const*, lldb_private::Broadcaster*, unsigned int, >> std::__1::shared_ptr<lldb_private::Event>&) + 27 >> 4 _lldb.so 0x000000011171de6c >> lldb_private::Process::WaitForStateChangedEvents(lldb_private::TimeValue >> const*, std::__1::shared_ptr<lldb_private::Event>&, lldb_private::Listener*) >> + 112 >> 5 _lldb.so 0x000000011171dc95 >> lldb_private::Process::WaitForProcessToStop(lldb_private::TimeValue const*, >> std::__1::shared_ptr<lldb_private::Event>*, bool, lldb_private::Listener*, >> lldb_private::Stream*) + 377 >> 6 _lldb.so 0x000000011172616a >> lldb_private::Process::HaltForDestroyOrDetach(std::__1::shared_ptr<lldb_private::Event>&) >> + 216 >> 7 _lldb.so 0x000000011171d8b0 >> lldb_private::Process::Destroy(bool) + 146 >> 8 _lldb.so 0x000000011171d56d >> lldb_private::Process::Finalize() + 91 >> 9 _lldb.so 0x00000001115173c4 >> lldb_private::Debugger::Clear() + 148 >> 10 _lldb.so 0x00000001115171fd >> lldb_private::Debugger::Destroy(std::__1::shared_ptr<lldb_private::Debugger>&) >> + 37 >> 11 _lldb.so 0x000000010f83c144 >> lldb::SBDebugger::Destroy(lldb::SBDebugger&) + 116 >> 12 _lldb.so 0x000000010f884daf >> _wrap_SBDebugger_Destroy(_object*, _object*) + 120 >> 13 org.python.python 0x000000010e53e75f PyEval_EvalFrameEx + >> 12761 >> >> >> On Thu, Feb 4, 2016 at 5:37 PM, Jim Ingham <jing...@apple.com> wrote: >> I don't know what: >> >> event_thread = LLDBListenerThread(debugger) >> >> does, but from your little sketch it looks like you are starting up a thread >> listening on this debugger, and so far as I can see you destroy the debugger >> out from under it without ever closing down that thread. That doesn't seem >> like a good idea. >> >> Jim >> >> >> >> >>> On Feb 4, 2016, at 5:27 PM, Jeffrey Tan via lldb-dev >>> <lldb-dev@lists.llvm.org> wrote: >>> >>> Hi, >>> >>> I am revising our lldb automation tests into async mode. However, I found >>> it randomly crashes depends on timing. And the crash happens mostly while >>> launching lldb twice in a row. I have narrowed down the code into a simple >>> repro below. Any assumption I made wrong with the LLDB API here? >>> >>> The crash stack seems to be not consistently. In the small repro below, the >>> crash stack is: >>> Crashed Thread: 0 Dispatch queue: com.apple.main-thread >>> >>> Exception Type: EXC_BAD_ACCESS (SIGSEGV) >>> Exception Codes: EXC_I386_GPFLT >>> >>> Thread 0 Crashed:: Dispatch queue: com.apple.main-thread >>> 0 _lldb.so 0x00000001088c7179 >>> EventMatcher::operator()(std::__1::shared_ptr<lldb_private::Event> const&) >>> const + 21 >>> 1 _lldb.so 0x00000001088c65d2 >>> lldb_private::Listener::FindNextEventInternal(lldb_private::Broadcaster*, >>> lldb_private::ConstString const*, unsigned int, unsigned int, >>> std::__1::shared_ptr<lldb_private::Event>&, bool) + 176 >>> 2 _lldb.so 0x00000001088c6952 >>> lldb_private::Listener::WaitForEventsInternal(lldb_private::TimeValue >>> const*, lldb_private::Broadcaster*, lldb_private::ConstString const*, >>> unsigned int, unsigned int, std::__1::shared_ptr<lldb_private::Event>&) + >>> 134 >>> 3 _lldb.so 0x00000001088c6ae9 >>> lldb_private::Listener::WaitForEventForBroadcasterWithType(lldb_private::TimeValue >>> const*, lldb_private::Broadcaster*, unsigned int, >>> std::__1::shared_ptr<lldb_private::Event>&) + 27 >>> 4 _lldb.so 0x0000000108abce6c >>> lldb_private::Process::WaitForStateChangedEvents(lldb_private::TimeValue >>> const*, std::__1::shared_ptr<lldb_private::Event>&, >>> lldb_private::Listener*) + 112 >>> 5 _lldb.so 0x0000000108abcc95 >>> lldb_private::Process::WaitForProcessToStop(lldb_private::TimeValue const*, >>> std::__1::shared_ptr<lldb_private::Event>*, bool, lldb_private::Listener*, >>> lldb_private::Stream*) + 377 >>> 6 _lldb.so 0x0000000108ac516a >>> lldb_private::Process::HaltForDestroyOrDetach(std::__1::shared_ptr<lldb_private::Event>&) >>> + 216 >>> 7 _lldb.so 0x0000000108abc8b0 >>> lldb_private::Process::Destroy(bool) + 146 >>> 8 _lldb.so 0x0000000108abc56d >>> lldb_private::Process::Finalize() + 91 >>> 9 _lldb.so 0x00000001088b63c4 >>> lldb_private::Debugger::Clear() + 148 >>> 10 _lldb.so 0x00000001088b61fd >>> lldb_private::Debugger::Destroy(std::__1::shared_ptr<lldb_private::Debugger>&) >>> + 37 >>> 11 _lldb.so 0x0000000106bdb144 >>> lldb::SBDebugger::Destroy(lldb::SBDebugger&) + 116 >>> 12 _lldb.so 0x0000000106c23daf >>> _wrap_SBDebugger_Destroy(_object*, _object*) + 120 >>> 13 org.python.python 0x00000001058dd75f PyEval_EvalFrameEx >>> + 12761 >>> >>> while in the real unit test it is crashing at: >>> Thread 12 Crashed: >>> 0 libsystem_kernel.dylib 0x00007fff8635a286 __pthread_kill + 10 >>> 1 libsystem_c.dylib 0x00007fff919409b3 abort + 129 >>> 2 libc++abi.dylib 0x00007fff8a94ea21 abort_message + 257 >>> 3 libc++abi.dylib 0x00007fff8a9769d1 >>> default_terminate_handler() + 267 >>> 4 libobjc.A.dylib 0x00007fff935e77eb _objc_terminate() >>> + 124 >>> 5 libc++abi.dylib 0x00007fff8a9740a1 >>> std::__terminate(void (*)()) + 8 >>> 6 libc++abi.dylib 0x00007fff8a973b30 __cxa_throw + 121 >>> 7 com.apple.LLDB.framework 0x000000010b994c6b >>> std::__1::shared_ptr<lldb_private::Process>::shared_ptr<lldb_private::Process>(std::__1::weak_ptr<lldb_private::Process> >>> const&, std::__1::enable_if<is_convertible<lldb_private::Process*, >>> lldb_private::Process*>::value, >>> std::__1::shared_ptr<lldb_private::Process>::__nat>::type) + 99 >>> 8 com.apple.LLDB.framework 0x000000010b8ac762 >>> lldb_private::Process::AppendSTDOUT(char const*, unsigned long) + 86 >>> 9 com.apple.LLDB.framework 0x000000010b6951d7 >>> lldb_private::Communication::ReadThread(void*) + 287 >>> 10 libsystem_pthread.dylib 0x00007fff8d92c05a _pthread_body + 131 >>> 11 libsystem_pthread.dylib 0x00007fff8d92bfd7 _pthread_start + >>> 176 >>> >>> >>> ================Repro Code==================== >>> >>> def wait_for_process_stop(process): >>> while not process.is_stopped: >>> time.sleep(0.1) >>> >>> def launch_debugging(debugger, stop_at_entry): >>> error = lldb.SBError() >>> listener = lldb.SBListener('Chrome Dev Tools Listener') >>> target = debugger.GetSelectedTarget() >>> process = target.Launch (listener, >>> None, # argv >>> None, # envp >>> None, # stdin_path >>> None, # stdout_path >>> None, # stderr_path >>> None, # working directory >>> 0, # launch flags >>> stop_at_entry, # Stop at entry >>> error) # error >>> print 'Launch result: %s' % str(error) >>> event_thread = LLDBListenerThread(debugger) >>> event_thread.start() >>> return process >>> >>> def do_test(): >>> debugger = lldb.SBDebugger.Create() >>> debugger.SetAsync(True) >>> target = debugger.CreateTargetWithFileAndArch(executable_path, >>> lldb.LLDB_ARCH_DEFAULT) >>> >>> process = launch_debugging(debugger, stop_at_entry=True) >>> >>> wait_for_process_stop(process) # wait for entry breakpoint. >>> target.BreakpointCreateByName('main') >>> process.Continue() >>> wait_for_process_stop(process) # wait for main breakpoint. >>> lldb.SBDebugger.Destroy(debugger) >>> >>> def main(): >>> do_test() >>> do_test() >>> _______________________________________________ >>> lldb-dev mailing list >>> lldb-dev@lists.llvm.org >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev >> >> >> >> _______________________________________________ >> lldb-dev mailing list >> lldb-dev@lists.llvm.org >> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev > > _______________________________________________ > lldb-dev mailing list > lldb-dev@lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev _______________________________________________ lldb-dev mailing list lldb-dev@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
