[lldb-dev] SBTarget::AttachToProcessWithID hangs

[Philippe Lavoie via lldb-dev]

It is a custom process plug-in using a proprietary protocol to communicate with the debug target.

In the process plugin's AsyncThread, I set the process private state to eStateStopped by calling process->SetPrivateState.
Is it enough to broadcast the state change?

The event is in the events log:

> 1442428969.471000000 004BC318 Broadcaster("lldb.process")::BroadcastEvent (event_sp = {00A723C8 Event: broadcaster = 004BC318 (lldb.process), type = 0x00000001(state-changed), data = { process = 004BC308 (pid = 1), state = stopped}}, unique =0) hijack = 00000000

-Philippe
________________________________________
From: Greg Clayton [gclayton at apple.com]
Sent: Wednesday, September 16, 2015 3:36 PM
To: Philippe Lavoie
Cc: lldb-dev at lists.llvm.org
Subject: Re: [lldb-dev] SBTarget::AttachToProcessWithID hangs

A few questions:

Which process plug-in does your debugging target use?
Is it a GDB Remote based debug session?
   If so is it using lldb-server?
   a custom GDB server?

In general, we expect to receive a eStateStopped process event if the attach is successful and this is what we are waiting for. If you have a custom Process subclass, you will need to make sure you stop your target and broadcast a eStateStopped event. If you are using GDB remote, please enable logging with the following line before calling AttachToProcessWithID:

debugger.HandleCommand("log enable -f /tmp/packets.txt gdb-remote packets");

Then run and watch things fail, and attach the log.

Greg Clayton

> On Sep 16, 2015, at 11:59 AM, Philippe Lavoie via lldb-dev <lldb-dev at lists.llvm.org> wrote:
>
>
> I am trying to attach to a stopped process on our dsp target using the SBTarget interface but the call hangs.
> What I understand is that it is waiting for events on the "lldb.process" broadcaster using the "lldb.Target.Attach.attach.hijack" listener.
>
> Enabling the logs, I see that the process is attached successfully and that the stop event is generated. It just seems that the event is not seen by the listener.
>
> 1442428969.321000000 004B9590 Listener::WaitForEventsInternal (timeout = { 00000000 }) for lldb.Target.Attach.attach.hijack
> 1442428969.321000000 004BC7F4 Broadcaster("opus.remote")::BroadcastEvent (event_sp = {00A72050 Event: broadcaster = 004BC7F4 (opus.remote), type = 0x00010000, data = <NULL>}, unique =0) hijack = 00000000
> 1442428969.341000000 0049AC50 Broadcaster("lldb.target")::BroadcastEvent (event_sp = {00A70C78 Event: broadcaster = 0049AC50 (lldb.target), type = 0x00000002 (modules-loaded), data = {}}, unique =0) hijack = 00000000
> 1442428969.341000000 004BC7F4 Broadcaster("opus.remote")::BroadcastEvent (event_sp = {00A723C8 Event: broadcaster = 004BC7F4 (opus.remote), type = 0x00010000, data = <NULL>}, unique =0) hijack = 00000000
> 1442428969.450000000 004BC394 Broadcaster("lldb.process.internal_state_broadcaster")::BroadcastEvent (event_sp = {00A723C8 Event: broadcaster = 004BC394 (lldb.process.internal_state_broadcaster), type = 0x00000001, data = { process = 004BC308 (pid = 1), state = stopped}}, unique =0) hijack = 00000000
> 1442428969.452000000 004BC42C Listener('lldb.process.internal_state_listener')::AddEvent (event_sp = {00A723C8})
> 1442428969.453000000 031CF700 Listener::WaitForEventsInternal (timeout = { 00000000 }) for ProcessOpusRemote::AsyncThread
> 1442428969.453000000 004BC42C 'lldb.process.internal_state_listener' Listener::FindNextEventInternal(broadcaster=00000000, broadcaster_names=00000000[0], event_type_mask=0x00000000, remove=1) event 00A723C8
> 1442428969.459000000 0309F8D4 Listener::StartListeningForEvents (broadcaster = 004BC5F4, mask = 0x00000020) acquired_mask = 0x00000020 for Communication::SyncronizeWithReadThread
> 1442428969.470000000 Process::ShouldBroadcastEvent (00A723C8) => new state: stopped, last broadcast state: stopped - YES
> 1442428969.471000000 004BC318 Broadcaster("lldb.process")::BroadcastEvent (event_sp = {00A723C8 Event: broadcaster = 004BC318 (lldb.process), type = 0x00000001(state-changed), data = { process = 004BC308 (pid = 1), state = stopped}}, unique =0) hijack = 00000000
> 1442428969.473000000 00402598 Listener('lldb.Debugger')::AddEvent (event_sp = {00A723C8})
> 1442428969.474000000 004BC42C Listener::WaitForEventsInternal (timeout = { 00000000 }) for lldb.process.internal_state_listener
>
> Here's the code I use to attach.
>
> SBDebugger::Initialize();
>
> SBDebugger debugger = lldb::SBDebugger::Create(false);
> debugger.SetAsync(true);
>
> const char* categories [] = { "process", "events", 0 };
> if (!debugger.EnableLog("lldb", categories))
> return -1;
>
> pid_t pid = 1;
>
> SBTarget target = debugger.CreateTargetWithFileAndArch(elffile_name, "opus2");
>
> SBError error;
> SBListener listener("test_listener");
>
> SBProcess process = target.AttachToProcessWithID(listener, pid, error);
>
> if (!process.IsValid())
> {
>    ...
>
>
> I would be grateful for any insight on the cause of this behavior.
>
> Thanks,
> -Philippe
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