[lldb] [llgs] Improve stdio forwarding in multiprocess+nonstop

Enable stdio forwarding when nonstop mode is enabled, and disable it
once it is disabled.  This makes it possible to cleanly handle stdio
forwarding while running multiple processes in non-stop mode.

Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.llvm.org/D128932

1 files changed, 17 insertions, 7 deletions

diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
index be789bd..5804c13 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
@@ -1113,14 +1113,16 @@ void GDBRemoteCommunicationServerLLGS::ProcessStateChanged(
     SendProcessOutput();
     // Then stop the forwarding, so that any late output (see llvm.org/pr25652)
     // does not interfere with our protocol.
-    StopSTDIOForwarding();
+    if (!m_non_stop)
+      StopSTDIOForwarding();
     HandleInferiorState_Stopped(process);
     break;
 
   case StateType::eStateExited:
     // Same as above
     SendProcessOutput();
-    StopSTDIOForwarding();
+    if (!m_non_stop)
+      StopSTDIOForwarding();
     HandleInferiorState_Exited(process);
     break;
 
@@ -1425,7 +1427,8 @@ GDBRemoteCommunication::PacketResult
 GDBRemoteCommunicationServerLLGS::Handle_k(StringExtractorGDBRemote &packet) {
   Log *log = GetLog(LLDBLog::Process);
 
-  StopSTDIOForwarding();
+  if (!m_non_stop)
+    StopSTDIOForwarding();
 
   if (m_debugged_processes.empty()) {
     LLDB_LOG(log, "No debugged process found.");
@@ -1451,7 +1454,8 @@ GDBRemoteCommunicationServerLLGS::Handle_k(StringExtractorGDBRemote &packet) {
 GDBRemoteCommunication::PacketResult
 GDBRemoteCommunicationServerLLGS::Handle_vKill(
     StringExtractorGDBRemote &packet) {
-  StopSTDIOForwarding();
+  if (!m_non_stop)
+    StopSTDIOForwarding();
 
   packet.SetFilePos(6); // vKill;
   uint32_t pid = packet.GetU32(LLDB_INVALID_PROCESS_ID, 16);
@@ -3524,7 +3528,8 @@ GDBRemoteCommunicationServerLLGS::Handle_vRun(
 GDBRemoteCommunication::PacketResult
 GDBRemoteCommunicationServerLLGS::Handle_D(StringExtractorGDBRemote &packet) {
   Log *log = GetLog(LLDBLog::Process);
-  StopSTDIOForwarding();
+  if (!m_non_stop)
+    StopSTDIOForwarding();
 
   lldb::pid_t pid = LLDB_INVALID_PROCESS_ID;
 
@@ -3923,6 +3928,8 @@ GDBRemoteCommunicationServerLLGS::Handle_QNonStop(
   assert(packet_str.startswith("QNonStop:"));
   packet_str.consume_front("QNonStop:");
   if (packet_str == "0") {
+    if (m_non_stop)
+      StopSTDIOForwarding();
     for (auto &process_it : m_debugged_processes) {
       if (process_it.second.process_up->IsRunning()) {
         assert(m_non_stop);
@@ -3945,6 +3952,8 @@ GDBRemoteCommunicationServerLLGS::Handle_QNonStop(
     if (m_disabling_non_stop)
       return PacketResult::Success;
   } else if (packet_str == "1") {
+    if (!m_non_stop)
+      StartSTDIOForwarding();
     m_non_stop = true;
   } else
     return SendErrorResponse(Status("Invalid QNonStop packet"));
@@ -4238,9 +4247,10 @@ void GDBRemoteCommunicationServerLLGS::SetEnabledExtensions(
 
 GDBRemoteCommunication::PacketResult
 GDBRemoteCommunicationServerLLGS::SendContinueSuccessResponse() {
-  // TODO: how to handle forwarding in non-stop mode?
+  if (m_non_stop)
+    return SendOKResponse();
   StartSTDIOForwarding();
-  return m_non_stop ? SendOKResponse() : PacketResult::Success;
+  return PacketResult::Success;
 }
 
 void GDBRemoteCommunicationServerLLGS::AppendThreadIDToResponse(