[Lldb-commits] [lldb] r247852 - Add an OperatingSystem plugin to support goroutines

Fri Jul 14 12:14:28 PDT 2017

Thanks Pavel, I got a bounce from his work email too. I agree with your plan for this, I think this is the first time that we have a plugin/target without an active maintainer that may be bitrotting or in need of maintenance. I was experimenting with disabling the goroutine threads, the change for that is just

diff --git i/source/Plugins/OperatingSystem/Go/OperatingSystemGo.cpp w/source/Plugins/OperatingSystem/Go/OperatingSystemGo.cpp
index c5a3ddee484..704f38121dd 100644
--- i/source/Plugins/OperatingSystem/Go/OperatingSystemGo.cpp
+++ w/source/Plugins/OperatingSystem/Go/OperatingSystemGo.cpp
@@ -47,7 +47,7 @@ using namespace lldb_private;
 namespace {
 
 static PropertyDefinition g_properties[] = {
- {"enable", OptionValue::eTypeBoolean, true, true, nullptr, nullptr,
+ {"enable", OptionValue::eTypeBoolean, true, false, nullptr, nullptr,
 "Specify whether goroutines should be treated as threads."},
 {NULL, OptionValue::eTypeInvalid, false, 0, NULL, NULL, NULL}};


I see a lot of people developing with go, I would not be surprised if we get some motivated go developers who will fix up the existing plugin for newer runtimes eventually. As long as it's not crashing, I'm in favor of leaving the plugins enabled as much as we can.


On 07/14/17 02:01 AM, Pavel Labath  <labath at google.com> wrote: 
> 
> Hi Jason,
> 
> I believe Ryan is no longer working for google. Since the go plugin
> was his effort, I think that unfortunately leaves our go support
> without a maintainer. (Unless he happens to be reading this from a
> personal email). I have also recently disabled one of the go tests
> because it was failing with go 1.8 (in wasn't crashing though, so I'm
> not sure if it is related to your problem).
> 
> I'm not sure if we have a policy on what to do in these cases, but I
> propose the following course of action:
> - disable goroutine support via the setting you mentioned
> - send out a call for maintainers to lldb-dev (I can forward that to
> google go team, to see if anyone wants to pick up that effort)
> - if nobody responds within a certain timeframe, delete the relevant code
> 
> 
> On 14 July 2017 at 04:58, Jason Molenda via lldb-commits
> <lldb-commits at lists.llvm.org> wrote:
> > Hi Ryan, we're having a tiny problem with the Go OperatingSystem plugin at Apple. I know it's been a while since you've worked on this, but I wanted to see if you had an opinion about how we should address this.
> >
> > Some iPhone app developers download static libraries (aka ranlib archives aka collection of .o files) to build into their projects, and we've seen a few static libraries that are written in Go. I have no idea what compilers were used to generate these object files.
> >
> > We go through the OperatingSystemGo::Init and find
> >
> > ValueObjectSP allgs_sp = FindGlobal(target_sp, "runtime.allgs");
> > if (allgs_sp) {
> > m_allg_sp = allgs_sp->GetChildMemberWithName(ConstString("array"), true);
> > m_allglen_sp = allgs_sp->GetChildMemberWithName(ConstString("len"), true);
> >
> > Then when we're working on threads (and the plugin.os.goroutines.enable setting is enabled), OperatingSystemGo::UpdateThreadList is called to add extra threads ("goroutines"? sorry I haven't had a chance to play with the language yet, I'm not familiar with the terminology) into lldb's thread list. It starts by getting the runtime.allgs.len:
> >
> > uint64_t allglen = m_allglen_sp->GetValueAsUnsigned(0);
> >
> > and then iterates over that many goroutines:
> >
> > Error err;
> > for (uint64_t i = 0; i < allglen; ++i) {
> > goroutines.push_back(CreateGoroutineAtIndex(i, err));
> > if (err.Fail()) {
> > err.PutToLog(log, "OperatingSystemGo::UpdateThreadList");
> > return new_thread_list.GetSize(false) > 0;
> > }
> >
> > and in OperatingSystemGo::CreateGoroutineAtIndex we do
> >
> > ValueObjectSP g =
> > m_allg_sp->GetSyntheticArrayMember(idx, true)->Dereference(err);
> >
> >
> > and this is where we're crashing. For some reason the runtime.allgs.len says it has 8 but m_allg_sp->GetSyntheticArrayMember(0, true) returns an empty ValueObjectSP (shared pointer) so we crash when we dereference it.
> >
> > Of course the real question is why does m_allg_sp->GetSyntheticArrayMember(0, true) not return a child -- it should have 8 of them according to runtime.allgs.len -- but I'm not super interested in this, the people who are developing/debugging these apps are unaware that they have go code in their program and are not going to be debugging into it.
> >
> >
> > I can avoid the crash by checking to see if we were able to fetch the child. If not, set the error object and return. UpdateThreadList() detects the error and doesn't add any goroutines to the lldb thread list. e.g.
> >
> > diff --git i/source/Plugins/OperatingSystem/Go/OperatingSystemGo.cpp w/source/Plugins/OperatingSystem/Go/OperatingSystemGo.cpp
> > index c5a3ddee484..97875c7266d 100644
> > --- i/source/Plugins/OperatingSystem/Go/OperatingSystemGo.cpp
> > +++ w/source/Plugins/OperatingSystem/Go/OperatingSystemGo.cpp
> > @@ -451,8 +451,14 @@ OperatingSystemGo::Goroutine
> > OperatingSystemGo::CreateGoroutineAtIndex(uint64_t idx, Error &err) {
> > err.Clear();
> > Goroutine result = {};
> > - ValueObjectSP g =
> > - m_allg_sp->GetSyntheticArrayMember(idx, true)->Dereference(err);
> > + ValueObjectSP child_sp = m_allg_sp->GetSyntheticArrayMember(idx, true);
> > + if (!child_sp) {
> > + err.SetErrorToGenericError();
> > + err.SetErrorString("unable to find goroutines in array");
> > + return result;
> > + }
> > +
> > + ValueObjectSP g = child_sp->Dereference(err);
> > if (err.Fail()) {
> > return result;
> > }
> >
> >
> > I could also just disable goroutines in the lldb that we ship in Xcode. I'd rather not do that because it means people working in go on macos/ios need to re-enable it in their .lldbinit files before they get the expected debug experience.
> >
> >
> > If you have a chance to look at this, could you let me know what you think is best here?
> >
> >
> > Thanks
> >
> > Jason
> >
> >
> >
> >
> >> On Sep 16, 2015, at 2:20 PM, Ryan Brown via lldb-commits <lldb-commits at lists.llvm.org> wrote:
> >>
> >> Author: ribrdb
> >> Date: Wed Sep 16 16:20:44 2015
> >> New Revision: 247852
> >>
> >> URL: http://llvm.org/viewvc/llvm-project?rev=247852&view=rev
> >> Log:
> >> Add an OperatingSystem plugin to support goroutines
> >>
> >> The Go runtime schedules user level threads (goroutines) across real threads.
> >> This adds an OS plugin to create memory threads for goroutines.
> >> It supports the 1.4 and 1.5 go runtime.
> >>
> >> Differential Revision: http://reviews.llvm.org/D5871
> >>
> >> Added:
> >> lldb/trunk/source/Plugins/OperatingSystem/Go/
> >> lldb/trunk/source/Plugins/OperatingSystem/Go/CMakeLists.txt
> >> lldb/trunk/source/Plugins/OperatingSystem/Go/Makefile
> >> lldb/trunk/source/Plugins/OperatingSystem/Go/OperatingSystemGo.cpp
> >> lldb/trunk/source/Plugins/OperatingSystem/Go/OperatingSystemGo.h
> >> lldb/trunk/test/lang/go/goroutines/
> >> lldb/trunk/test/lang/go/goroutines/TestGoroutines.py
> >> lldb/trunk/test/lang/go/goroutines/main.go
> >> Modified:
> >> lldb/trunk/cmake/LLDBDependencies.cmake
> >> lldb/trunk/include/lldb/Core/PluginManager.h
> >> lldb/trunk/include/lldb/lldb-enumerations.h
> >> lldb/trunk/lib/Makefile
> >> lldb/trunk/lldb.xcodeproj/project.pbxproj
> >> lldb/trunk/source/Core/PluginManager.cpp
> >> lldb/trunk/source/Initialization/SystemInitializerCommon.cpp
> >> lldb/trunk/source/Plugins/Makefile
> >> lldb/trunk/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
> >> lldb/trunk/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
> >> lldb/trunk/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp
> >> lldb/trunk/source/Plugins/OperatingSystem/CMakeLists.txt
> >> lldb/trunk/source/Plugins/OperatingSystem/Python/OperatingSystemPython.cpp
> >> lldb/trunk/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
> >> lldb/trunk/source/Symbol/ObjectFile.cpp
> >> lldb/trunk/source/Target/Process.cpp
> >> lldb/trunk/source/Target/StackFrameList.cpp
> >> lldb/trunk/source/Target/ThreadList.cpp
> >> lldb/trunk/source/Utility/ConvertEnum.cpp
> >>
> >
> > _______________________________________________
> > lldb-commits mailing list
> > lldb-commits at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
> 
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