[Lldb-commits] [PATCH] fix lldb-mi hang on OSX

Tue Dec 2 01:58:09 PST 2014

Thank you for reviewing!

On Fri, Nov 28, 2014 at 10:02:33AM +0000, Abid, Hafiz wrote:
> Hi Dawn,
> I looked at the patch a bit. It looks ok to use select to check if the input is available before blocking on fgets. But I am still wondering why you need extra "return" in case of -exec-run. It seems to work ok on Linux. Where is it blocking in OSX? Btw, if the problem is only with gdb-exit then an extra check for it where we check for "quit" will work too.

I can't explain why it works on Linux (although I assumed it must), but on
OSX, if you attach you'll see that it is waiting on a mutex.  You can see
where in the following example:

debug session in lldb-mi showing hang after -exec-run:
    yippie:~/llvm_trunk$$LLDBMI_EXEC --interpreter
    (gdb)
    -file-exec-and-symbols ~/tmp/a.out
    ^done
    -break-insert -f main
    =breakpoint-modified,bkpt={number="1",type="breakpoint",disp="keep",enabled="y",addr="0xffffffff",func="main",file="x.cpp",fullname="/Users/dawn/tmp/x.cpp",line="5",pending=["main"],times="0",original-location="main"}
    ^done,bkpt={number="1",type="breakpoint",disp="keep",enabled="y",addr="0xffffffff",func="main",file="x.cpp",fullname="/Users/dawn/tmp/x.cpp",line="5",pending=["main"],times="1",original-location="main"}
    -exec-run

attaching to lldb-mi to see what's up:
    yippie:~/cppstd/source$~/llvm_delphi/build_ninja/bin/lldb
    (lldb) attach 27893
    Process 27893 stopped
    * thread #1: tid = 0xf7a813, 0x00007fff90dad746 libsystem_kernel.dylib`__psynch_mutexwait + 10, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
	frame #0: 0x00007fff90dad746 libsystem_kernel.dylib`__psynch_mutexwait + 10
    -> 0x7fff90dad746 <__psynch_mutexwait+10>: jae    0x7fff90dad750            ; __psynch_mutexwait + 20
    0x7fff90dad748 <__psynch_mutexwait+12>: movq   %rax, %rdi
    0x7fff90dad74b <__psynch_mutexwait+15>: jmp    0x7fff90daa175            ; cerror_nocancel
    0x7fff90dad750 <__psynch_mutexwait+20>: retq

    Executable module set to "/Users/dawn/llvm_trunk/build_ninja/bin/lldb-mi".
    Architecture set to: x86_64-apple-macosx.
    (lldb) bt
    * thread #1: tid = 0xf7a813, 0x00007fff90dad746 libsystem_kernel.dylib`__psynch_mutexwait + 10, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
    * frame #0: 0x00007fff90dad746 libsystem_kernel.dylib`__psynch_mutexwait + 10
	frame #1: 0x00007fff8f51b779 libsystem_pthread.dylib`_pthread_mutex_lock + 372
	frame #2: 0x00007fff92ea5edd libsystem_c.dylib`flockfile + 37
	frame #3: 0x00007fff92ea6e74 libsystem_c.dylib`fileno + 15
	frame #4: 0x0000000107dff2b8 liblldb.3.6.0.dylib`lldb_private::File::GetDescriptor(this=0x00007fe9b94420d8) const + 88 at File.cpp:146
	frame #5: 0x0000000107ec557c liblldb.3.6.0.dylib`lldb_private::IOHandler::GetInputFD(this=0x00007fe9b965f4d0) + 92 at IOHandler.cpp:85
	frame #6: 0x00000001082831b8 liblldb.3.6.0.dylib`IOHandlerProcessSTDIO(this=0x00007fe9b965f4d0, process=0x00007fe9ba031800, write_fd=5) + 184 at Process.cpp:4910
	frame #7: 0x00000001082797c3 liblldb.3.6.0.dylib`IOHandlerProcessSTDIO(this=0x00007fe9b965f4d0, process=0x00007fe9ba031800, write_fd=5) + 35 at Process.cpp:4911
	frame #8: 0x000000010826df42 liblldb.3.6.0.dylib`lldb_private::Process::SetSTDIOFileDescriptor(this=0x00007fe9ba031800, fd=5) + 642 at Process.cpp:5100
	frame #9: 0x000000010824fd8e liblldb.3.6.0.dylib`lldb_private::Platform::DebugProcess(this=0x00007fe9b9528c10, launch_info=0x00007fff598962a8, debugger=0x00007fe9b9870c00, target=0x00007fe9b9880000, error=0x00007fff59896270) + 1406 at Platform.cpp:1138
	frame #10: 0x00000001085349f4 liblldb.3.6.0.dylib`PlatformPOSIX::DebugProcess(this=0x00007fe9b9528c10, launch_info=0x00007fff598962a8, debugger=0x00007fe9b9870c00, target=0x00007fe9b9880000, error=0x00007fff59896270) + 244 at PlatformPOSIX.cpp:875
	frame #11: 0x00000001082cfde8 liblldb.3.6.0.dylib`lldb_private::Target::Launch(this=0x00007fe9b9880000, launch_info=0x00007fff598962a8, stream=0x0000000000000000) + 1944 at Target.cpp:2462
	frame #12: 0x0000000108672c58 liblldb.3.6.0.dylib`lldb::SBTarget::Launch(this=0x0000000106469178, listener=0x0000000106469400, argv=0x0000000000000000, envp=0x0000000000000000, stdin_path=0x0000000000000000, stdout_path=0x0000000000000000, stderr_path=0x0000000000000000, working_directory=0x0000000000000000, launch_flags=2, stop_at_entry=false, error=0x00007fff59896838) + 2088 at SBTarget.cpp:779
	frame #13: 0x00000001063aabea lldb-mi`CMICmdCmdExecRun::Execute(this=0x00007fe9ba851200) + 234 at MICmdCmdExec.cpp:94
	frame #14: 0x00000001063ab3cc lldb-mi`non-virtual thunk to CMICmdCmdExecRun::Execute(this=0x00007fe9ba851240) + 28 at MICmdCmdExec.cpp:113
	frame #15: 0x00000001063e5230 lldb-mi`CMICmdInvoker::CmdExecute(this=0x00000001064688e0, vCmd=0x00007fe9ba851200) + 272 at MICmdInvoker.cpp:216
	frame #16: 0x00000001063ea1b4 lldb-mi`CMICmdMgr::CmdExecute(this=0x00000001064698a0, vCmdData=0x00007fff598976b8) + 804 at MICmdMgr.cpp:211
	frame #17: 0x0000000106434ea6 lldb-mi`CMIDriver::ExecuteCommand(this=0x0000000106468bc0, vCmdData=0x00007fff598976b8) + 38 at MIDriver.cpp:1057
	frame #18: 0x0000000106433e23 lldb-mi`CMIDriver::InterpretCommandThisDriver(this=0x0000000106468bc0, vTextLine=0x00007fff59897d68, vwbCmdYesValid=0x00007fff59897cff) + 195 at MIDriver.cpp:1009
	frame #19: 0x0000000106433477 lldb-mi`CMIDriver::InterpretCommand(this=0x0000000106468bc0, vTextLine=0x00007fff59897d68) + 55 at MIDriver.cpp:973
	frame #20: 0x00000001064332eb lldb-mi`CMIDriver::ReadStdinLineQueue(this=0x0000000106468bc0) + 651 at MIDriver.cpp:690
	frame #21: 0x0000000106432f9f lldb-mi`CMIDriver::DoMainLoop(this=0x0000000106468bc0) + 447 at MIDriver.cpp:630
	frame #22: 0x000000010643342c lldb-mi`non-virtual thunk to CMIDriver::DoMainLoop(this=0x0000000106468c00) + 28 at MIDriver.cpp:647
	frame #23: 0x0000000106442722 lldb-mi`CMIDriverMgr::DriverMainLoop(this=0x0000000106469500) + 66 at MIDriverMgr.cpp:344
	frame #24: 0x0000000106440311 lldb-mi`main(argc=2, argv=0x00007fff59898308) + 321 at MIDriverMain.cpp:352
	frame #25: 0x00007fff8b32a5fd libdyld.dylib`start + 1
	frame #26: 0x00007fff8b32a5fd libdyld.dylib`start + 1
    (lldb)

I've offered to make the patch OSX-specific if that is preferred?

Thanks,
-Dawn