[lldb] Synchronize output through the IOHandler

Add synchronization to the IOHandler to prevent multiple threads from
writing concurrently to the output or error stream.

A scenario where this could happen is when a thread (the default event
thread for example) is using the debugger's asynchronous stream. We
would delegate this operation to the IOHandler which might be running on
another thread. Until this patch there was nothing to synchronize the
two at the IOHandler level.

Differential revision: https://reviews.llvm.org/D121500

lldb/include/lldb/Core/IOHandler.h

@@ -165,11 +165,14 @@ public:
 
   virtual void PrintAsync(const char *s, size_t len, bool is_stdout);
 
+  std::mutex &GetOutputMutex() { return m_output_mutex; }
+
 protected:
   Debugger &m_debugger;
   lldb::FileSP m_input_sp;
   lldb::StreamFileSP m_output_sp;
   lldb::StreamFileSP m_error_sp;
+  std::mutex m_output_mutex;
   repro::DataRecorder *m_data_recorder;
   Predicate<bool> m_popped;
   Flags m_flags;

lldb/include/lldb/Host/Editline.h

@@ -154,7 +154,7 @@ using namespace line_editor;
 class Editline {
 public:
   Editline(const char *editor_name, FILE *input_file, FILE *output_file,
-           FILE *error_file, bool color_prompts);
+           FILE *error_file, std::mutex &output_mutex, bool color_prompts);
 
   ~Editline();
 
@@ -402,7 +402,7 @@ private:
   std::string m_suggestion_ansi_suffix;
 
   std::size_t m_previous_autosuggestion_size = 0;
-  std::mutex m_output_mutex;
+  std::mutex &m_output_mutex;
 };
 }
 

lldb/include/lldb/Interpreter/CommandInterpreter.h

@@ -655,7 +655,8 @@ private:
                               const CommandObject::CommandMap &command_map);
 
   // An interruptible wrapper around the stream output
-  void PrintCommandOutput(Stream &stream, llvm::StringRef str);
+  void PrintCommandOutput(IOHandler &io_handler, llvm::StringRef str,
+                          bool is_stdout);
 
   bool EchoCommandNonInteractive(llvm::StringRef line,
                                  const Flags &io_handler_flags) const;

lldb/source/Core/IOHandler.cpp

@@ -123,6 +123,7 @@ void IOHandler::SetPopped(bool b) { m_popped.SetValue(b, eBroadcastOnChange); }
 void IOHandler::WaitForPop() { m_popped.WaitForValueEqualTo(true); }
 
 void IOHandler::PrintAsync(const char *s, size_t len, bool is_stdout) {
+  std::lock_guard<std::mutex> guard(m_output_mutex);
   lldb::StreamFileSP stream = is_stdout ? m_output_sp : m_error_sp;
   stream->Write(s, len);
   stream->Flush();
@@ -266,9 +267,9 @@ IOHandlerEditline::IOHandlerEditline(
                  m_input_sp && m_input_sp->GetIsRealTerminal();
 
   if (use_editline) {
-    m_editline_up = std::make_unique<Editline>(editline_name, GetInputFILE(),
-                                               GetOutputFILE(), GetErrorFILE(),
-                                               m_color_prompts);
+    m_editline_up = std::make_unique<Editline>(
+        editline_name, GetInputFILE(), GetOutputFILE(), GetErrorFILE(),
+        GetOutputMutex(), m_color_prompts);
     m_editline_up->SetIsInputCompleteCallback(
         [this](Editline *editline, StringList &lines) {
           return this->IsInputCompleteCallback(editline, lines);
@@ -619,6 +620,7 @@ void IOHandlerEditline::GotEOF() {
 void IOHandlerEditline::PrintAsync(const char *s, size_t len, bool is_stdout) {
 #if LLDB_ENABLE_LIBEDIT
   if (m_editline_up) {
+    std::lock_guard<std::mutex> guard(m_output_mutex);
     lldb::StreamFileSP stream = is_stdout ? m_output_sp : m_error_sp;
     m_editline_up->PrintAsync(stream.get(), s, len);
   } else

lldb/source/Host/common/Editline.cpp

@@ -1376,10 +1376,12 @@ Editline *Editline::InstanceFor(EditLine *editline) {
 }
 
 Editline::Editline(const char *editline_name, FILE *input_file,
-                   FILE *output_file, FILE *error_file, bool color_prompts)
+                   FILE *output_file, FILE *error_file,
+                   std::mutex &output_mutex, bool color_prompts)
     : m_editor_status(EditorStatus::Complete), m_color_prompts(color_prompts),
       m_input_file(input_file), m_output_file(output_file),
-      m_error_file(error_file), m_input_connection(fileno(input_file), false) {
+      m_error_file(error_file), m_input_connection(fileno(input_file), false),
+      m_output_mutex(output_mutex) {
   // Get a shared history instance
   m_editor_name = (editline_name == nullptr) ? "lldb-tmp" : editline_name;
   m_history_sp = EditlineHistory::GetHistory(m_editor_name);

lldb/source/Interpreter/CommandInterpreter.cpp

@@ -2975,8 +2975,12 @@ bool CommandInterpreter::WasInterrupted() const {
   return was_interrupted;
 }
 
-void CommandInterpreter::PrintCommandOutput(Stream &stream,
-                                            llvm::StringRef str) {
+void CommandInterpreter::PrintCommandOutput(IOHandler &io_handler,
+                                            llvm::StringRef str,
+                                            bool is_stdout) {
+
+  lldb::StreamFileSP stream = is_stdout ? io_handler.GetOutputStreamFileSP()
+                                        : io_handler.GetErrorStreamFileSP();
   // Split the output into lines and poll for interrupt requests
   const char *data = str.data();
   size_t size = str.size();
@@ -2989,15 +2993,19 @@ void CommandInterpreter::PrintCommandOutput(Stream &stream,
         break;
       }
     }
-    chunk_size = stream.Write(data, chunk_size);
+    {
+      std::lock_guard<std::mutex> guard(io_handler.GetOutputMutex());
+      chunk_size = stream->Write(data, chunk_size);
+    }
     lldbassert(size >= chunk_size);
     data += chunk_size;
     size -= chunk_size;
   }
-  if (size > 0) {
-    stream.Printf("\n... Interrupted.\n");
-  }
-  stream.Flush();
+
+  std::lock_guard<std::mutex> guard(io_handler.GetOutputMutex());
+  if (size > 0)
+    stream->Printf("\n... Interrupted.\n");
+  stream->Flush();
 }
 
 bool CommandInterpreter::EchoCommandNonInteractive(
@@ -3033,9 +3041,11 @@ void CommandInterpreter::IOHandlerInputComplete(IOHandler &io_handler,
     // When using a non-interactive file handle (like when sourcing commands
     // from a file) we need to echo the command out so we don't just see the
     // command output and no command...
-    if (EchoCommandNonInteractive(line, io_handler.GetFlags()))
+    if (EchoCommandNonInteractive(line, io_handler.GetFlags())) {
+      std::lock_guard<std::mutex> guard(io_handler.GetOutputMutex());
       io_handler.GetOutputStreamFileSP()->Printf(
           "%s%s\n", io_handler.GetPrompt(), line.c_str());
+    }
   }
 
   StartHandlingCommand();
@@ -3057,13 +3067,13 @@ void CommandInterpreter::IOHandlerInputComplete(IOHandler &io_handler,
 
     if (!result.GetImmediateOutputStream()) {
       llvm::StringRef output = result.GetOutputData();
-      PrintCommandOutput(*io_handler.GetOutputStreamFileSP(), output);
+      PrintCommandOutput(io_handler, output, true);
     }
 
     // Now emit the command error text from the command we just executed
     if (!result.GetImmediateErrorStream()) {
       llvm::StringRef error = result.GetErrorData();
-      PrintCommandOutput(*io_handler.GetErrorStreamFileSP(), error);
+      PrintCommandOutput(io_handler, error, false);
     }
   }
 

lldb/unittests/Editline/EditlineTest.cpp

@@ -84,6 +84,7 @@ private:
   bool IsInputComplete(lldb_private::Editline *editline,
                        lldb_private::StringList &lines);
 
+  std::mutex output_mutex;
   std::unique_ptr<lldb_private::Editline> _editline_sp;
 
   PseudoTerminal _pty;
@@ -117,7 +118,7 @@ EditlineAdapter::EditlineAdapter()
   // Create an Editline instance.
   _editline_sp.reset(new lldb_private::Editline(
       "gtest editor", *_el_secondary_file, *_el_secondary_file,
-      *_el_secondary_file, false));
+      *_el_secondary_file, output_mutex, false));
   _editline_sp->SetPrompt("> ");
 
   // Hookup our input complete callback.