Fix a deadlock in the Python interpreter vrs. SIGINT.

The interpreter gets invoked in the sigint handler to cancel
long-running Python operations.  That requires the interpreter
lock, but that may be held by the Python operation that's getting
interrupted, so the mutex needs to be recursive.

<rdar://problem/33179086>

llvm-svn: 307942

lldb/include/lldb/Interpreter/CommandInterpreter.h

@@ -539,7 +539,7 @@ private:
   std::string m_repeat_command; // Stores the command that will be executed for
                                 // an empty command string.
   lldb::ScriptInterpreterSP m_script_interpreter_sp;
-  std::mutex m_script_interpreter_mutex;
+  std::recursive_mutex m_script_interpreter_mutex;
   lldb::IOHandlerSP m_command_io_handler_sp;
   char m_comment_char;
   bool m_batch_command_mode;

lldb/source/Interpreter/CommandInterpreter.cpp

@@ -2475,7 +2475,7 @@ void CommandInterpreter::HandleCommandsFromFile(
 }
 
 ScriptInterpreter *CommandInterpreter::GetScriptInterpreter(bool can_create) {
-  std::lock_guard<std::mutex> locker(m_script_interpreter_mutex);
+  std::lock_guard<std::recursive_mutex> locker(m_script_interpreter_mutex);
   if (!m_script_interpreter_sp) {
     if (!can_create)
       return nullptr;