[all-commits] [llvm/llvm-project] 1a8d9a: [lldb] Fix data race in ThreadedCommunication

[Jonas Devlieghere via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1a8d9a7657bba79099e6e2a6b0568db53d1e9a23
      https://github.com/llvm/llvm-project/commit/1a8d9a7657bba79099e6e2a6b0568db53d1e9a23
  Author: Jonas Devlieghere <jonas at devlieghere.com>
  Date:   2023-08-09 (Wed, 09 Aug 2023)

  Changed paths:
    M lldb/include/lldb/Core/ThreadedCommunication.h
    M lldb/source/Core/ThreadedCommunication.cpp

  Log Message:
  -----------
  [lldb] Fix data race in ThreadedCommunication

TSan reports the following race:

  Write of size 8 at 0x000107707ee8 by main thread:
    #0 lldb_private::ThreadedCommunication::StartReadThread(...) ThreadedCommunication.cpp:175
    #1 lldb_private::Process::SetSTDIOFileDescriptor(...) Process.cpp:4533
    #2 lldb_private::Platform::DebugProcess(...) Platform.cpp:1121
    #3 lldb_private::PlatformDarwin::DebugProcess(...) PlatformDarwin.cpp:711
    #4 lldb_private::Target::Launch(...) Target.cpp:3235
    #5 CommandObjectProcessLaunch::DoExecute(...) CommandObjectProcess.cpp:256
    #6 lldb_private::CommandObjectParsed::Execute(...) CommandObject.cpp:751
    #7 lldb_private::CommandInterpreter::HandleCommand(...) CommandInterpreter.cpp:2054

  Previous read of size 8 at 0x000107707ee8 by thread T5:
    #0 lldb_private::HostThread::IsJoinable(...) const HostThread.cpp:30
    #1 lldb_private::ThreadedCommunication::StopReadThread(...) ThreadedCommunication.cpp:192
    #2 lldb_private::Process::ShouldBroadcastEvent(...) Process.cpp:3420
    #3 lldb_private::Process::HandlePrivateEvent(...) Process.cpp:3728
    #4 lldb_private::Process::RunPrivateStateThread(...) Process.cpp:3914
    #5 std::__1::__function::__func<lldb_private::Process::StartPrivateStateThread(...) function.h:356
    #6 lldb_private::HostNativeThreadBase::ThreadCreateTrampoline(...) HostNativeThreadBase.cpp:62
    #7 lldb_private::HostThreadMacOSX::ThreadCreateTrampoline(...) HostThreadMacOSX.mm:18

The problem is the lack of synchronization between starting and stopping
the read thread. This patch fixes that by protecting those operations
with a mutex.

Differential revision: https://reviews.llvm.org/D157361