Re-land "[lldb] Synchronize output through the IOHandler"

JDevlieghere · JDevlieghere · commit 5418f63390a3 · 2022-03-29T13:42:28.000-07:00
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 (cherry picked from commit 8e776bb)
diff --git a/lldb/include/lldb/Core/IOHandler.h b/lldb/include/lldb/Core/IOHandler.h
@@ -34,7 +34,7 @@ class Debugger;
 namespace repro {
 class DataRecorder;
 }
-}
+} // namespace lldb_private
 
 namespace curses {
 class Application;
@@ -165,11 +165,14 @@ class IOHandler {
 
   virtual void PrintAsync(const char *s, size_t len, bool is_stdout);
 
+  std::recursive_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::recursive_mutex m_output_mutex;
   repro::DataRecorder *m_data_recorder;
   Predicate<bool> m_popped;
   Flags m_flags;
diff --git a/lldb/include/lldb/Host/Editline.h b/lldb/include/lldb/Host/Editline.h
@@ -154,7 +154,8 @@ 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::recursive_mutex &output_mutex,
+           bool color_prompts);
 
   ~Editline();
 
@@ -402,7 +403,7 @@ class Editline {
   std::string m_suggestion_ansi_suffix;
 
   std::size_t m_previous_autosuggestion_size = 0;
-  std::mutex m_output_mutex;
+  std::recursive_mutex &m_output_mutex;
 };
 }
 
diff --git a/lldb/include/lldb/Interpreter/CommandInterpreter.h b/lldb/include/lldb/Interpreter/CommandInterpreter.h
@@ -654,7 +654,8 @@ class CommandInterpreter : public Broadcaster,
                               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;
diff --git a/lldb/source/Core/IOHandler.cpp b/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::recursive_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);
@@ -622,6 +623,7 @@ 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::recursive_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
diff --git a/lldb/source/Host/common/Editline.cpp b/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::recursive_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);
@@ -1388,20 +1390,22 @@ Editline::Editline(const char *editline_name, FILE *input_file,
   if (m_output_file) {
     const int term_fd = fileno(m_output_file);
     if (term_fd != -1) {
-      static std::mutex *g_init_terminal_fds_mutex_ptr = nullptr;
+      static std::recursive_mutex *g_init_terminal_fds_mutex_ptr = nullptr;
       static std::set<int> *g_init_terminal_fds_ptr = nullptr;
       static llvm::once_flag g_once_flag;
       llvm::call_once(g_once_flag, [&]() {
         g_init_terminal_fds_mutex_ptr =
-            new std::mutex(); // NOTE: Leak to avoid C++ destructor chain issues
+            new std::recursive_mutex(); // NOTE: Leak to avoid C++ destructor
+                                        // chain issues
         g_init_terminal_fds_ptr = new std::set<int>(); // NOTE: Leak to avoid
                                                        // C++ destructor chain
                                                        // issues
       });
 
       // We must make sure to initialize the terminal a given file descriptor
       // only once. If we do this multiple times, we start leaking memory.
-      std::lock_guard<std::mutex> guard(*g_init_terminal_fds_mutex_ptr);
+      std::lock_guard<std::recursive_mutex> guard(
+          *g_init_terminal_fds_mutex_ptr);
       if (g_init_terminal_fds_ptr->find(term_fd) ==
           g_init_terminal_fds_ptr->end()) {
         g_init_terminal_fds_ptr->insert(term_fd);
@@ -1473,7 +1477,7 @@ uint32_t Editline::GetCurrentLine() { return m_current_line_index; }
 
 bool Editline::Interrupt() {
   bool result = true;
-  std::lock_guard<std::mutex> guard(m_output_mutex);
+  std::lock_guard<std::recursive_mutex> guard(m_output_mutex);
   if (m_editor_status == EditorStatus::Editing) {
     fprintf(m_output_file, "^C\n");
     result = m_input_connection.InterruptRead();
@@ -1484,7 +1488,7 @@ bool Editline::Interrupt() {
 
 bool Editline::Cancel() {
   bool result = true;
-  std::lock_guard<std::mutex> guard(m_output_mutex);
+  std::lock_guard<std::recursive_mutex> guard(m_output_mutex);
   if (m_editor_status == EditorStatus::Editing) {
     MoveCursor(CursorLocation::EditingCursor, CursorLocation::BlockStart);
     fprintf(m_output_file, ANSI_CLEAR_BELOW);
@@ -1499,7 +1503,7 @@ bool Editline::GetLine(std::string &line, bool &interrupted) {
   m_input_lines = std::vector<EditLineStringType>();
   m_input_lines.insert(m_input_lines.begin(), EditLineConstString(""));
 
-  std::lock_guard<std::mutex> guard(m_output_mutex);
+  std::lock_guard<std::recursive_mutex> guard(m_output_mutex);
 
   lldbassert(m_editor_status != EditorStatus::Editing);
   if (m_editor_status == EditorStatus::Interrupted) {
@@ -1544,7 +1548,7 @@ bool Editline::GetLines(int first_line_number, StringList &lines,
   m_input_lines = std::vector<EditLineStringType>();
   m_input_lines.insert(m_input_lines.begin(), EditLineConstString(""));
 
-  std::lock_guard<std::mutex> guard(m_output_mutex);
+  std::lock_guard<std::recursive_mutex> guard(m_output_mutex);
   // Begin the line editing loop
   DisplayInput();
   SetCurrentLine(0);
@@ -1574,7 +1578,7 @@ bool Editline::GetLines(int first_line_number, StringList &lines,
 }
 
 void Editline::PrintAsync(Stream *stream, const char *s, size_t len) {
-  std::lock_guard<std::mutex> guard(m_output_mutex);
+  std::lock_guard<std::recursive_mutex> guard(m_output_mutex);
   if (m_editor_status == EditorStatus::Editing) {
     MoveCursor(CursorLocation::EditingCursor, CursorLocation::BlockStart);
     fprintf(m_output_file, ANSI_CLEAR_BELOW);
diff --git a/lldb/source/Interpreter/CommandInterpreter.cpp b/lldb/source/Interpreter/CommandInterpreter.cpp
@@ -2969,8 +2969,12 @@ 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();
@@ -2983,14 +2987,19 @@ void CommandInterpreter::PrintCommandOutput(Stream &stream,
         break;
       }
     }
-    chunk_size = stream.Write(data, chunk_size);
+    {
+      std::lock_guard<std::recursive_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");
-  }
+
+  std::lock_guard<std::recursive_mutex> guard(io_handler.GetOutputMutex());
+  if (size > 0)
+    stream->Printf("\n... Interrupted.\n");
+  stream->Flush();
 }
 
 bool CommandInterpreter::EchoCommandNonInteractive(
@@ -3026,9 +3035,11 @@ 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::recursive_mutex> guard(io_handler.GetOutputMutex());
       io_handler.GetOutputStreamFileSP()->Printf(
           "%s%s\n", io_handler.GetPrompt(), line.c_str());
+    }
   }
 
   StartHandlingCommand();
@@ -3050,13 +3061,13 @@ 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);
     }
   }
 
diff --git a/lldb/unittests/Editline/EditlineTest.cpp b/lldb/unittests/Editline/EditlineTest.cpp
@@ -84,6 +84,7 @@ class EditlineAdapter {
   bool IsInputComplete(lldb_private::Editline *editline,
                        lldb_private::StringList &lines);
 
+  std::recursive_mutex output_mutex;
   std::unique_ptr<lldb_private::Editline> _editline_sp;
 
   PseudoTerminal _pty;
@@ -118,7 +119,7 @@ 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.
