[all-commits] [llvm/llvm-project] 0bdbe7: [lldb] Fix data race in ConnectionFileDescriptor

[Jonas Devlieghere via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0bdbe7bd7f1589817495a60cc8422df49575b17b
      https://github.com/llvm/llvm-project/commit/0bdbe7bd7f1589817495a60cc8422df49575b17b
  Author: Jonas Devlieghere <jonas at devlieghere.com>
  Date:   2023-08-07 (Mon, 07 Aug 2023)

  Changed paths:
    M lldb/include/lldb/Host/posix/ConnectionFileDescriptorPosix.h
    M lldb/source/Host/posix/ConnectionFileDescriptorPosix.cpp

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

TSan reports the following data race:

  Write of size 4 at 0x000109e0b160 by thread T2 (mutexes: write M0, write M1):
    #0 NativeFile::Close() File.cpp:329
    #1 ConnectionFileDescriptor::Disconnect(lldb_private::Status*) ConnectionFileDescriptorPosix.cpp:232
    #2 Communication::Disconnect(lldb_private::Status*) Communication.cpp:61
    #3 process_gdb_remote::ProcessGDBRemote::DidExit() ProcessGDBRemote.cpp:1164
    #4 Process::SetExitStatus(int, char const*) Process.cpp:1097
    #5 process_gdb_remote::ProcessGDBRemote::MonitorDebugserverProcess(...) ProcessGDBRemote.cpp:3387

  Previous read of size 4 at 0x000109e0b160 by main thread (mutexes: write M2):
    #0 NativeFile::IsValid() const File.h:393
    #1 ConnectionFileDescriptor::IsConnected() const ConnectionFileDescriptorPosix.cpp:121
    #2 Communication::IsConnected() const Communication.cpp:79
    #3 process_gdb_remote::GDBRemoteCommunication::WaitForPacketNoLock(...) GDBRemoteCommunication.cpp:256
    #4 process_gdb_remote::GDBRemoteCommunication::WaitForPacketNoLock(...l) GDBRemoteCommunication.cpp:244
    #5 process_gdb_remote::GDBRemoteClientBase::SendPacketAndWaitForResponseNoLock(llvm::StringRef, StringExtractorGDBRemote&) GDBRemoteClientBase.cpp:246

The problem is that in WaitForPacketNoLock's run loop, it checks that
the connection is still connected. This races with the
ConnectionFileDescriptor disconnecting. Most (but not all) access to the
IOObject in ConnectionFileDescriptorPosix is already gated by the mutex.
This patch just protects IsConnected in the same way.

Differential revision: https://reviews.llvm.org/D157347