add workaround to prohibit to pass arguments to thread_create helper …

…method

lib/fluent/plugin/output.rb

@@ -321,7 +321,9 @@ def start
           @buffer_config.flush_threads.times do |i|
             thread_title = "flush_thread_#{i}".to_sym
             thread_state = FlushThreadState.new(nil, nil)
-            thread = thread_create(thread_title, thread_state, &method(:flush_thread_run))
+            thread = thread_create(thread_title) do
+              flush_thread_run(thread_state)
+            end
             thread_state.thread = thread
             @output_flush_threads_mutex.synchronize do
               @output_flush_threads << thread_state

lib/fluent/plugin_helper/thread.rb

@@ -37,20 +37,27 @@ def thread_wait_until_start
         end
       end
 
-      def thread_create(title, *args)
+      # Ruby 2.2.3 or earlier (and all 2.1.x) cause bug about Threading ("Stack consistency error")
+      #  by passing splatted argument to `yield`
+      # https://bugs.ruby-lang.org/issues/11027
+      # We can enable to pass arguments after expire of Ruby 2.1 (& older 2.2.x)
+      # def thread_create(title, *args)
+      #   Thread.new(*args) do |*t_args|
+      #     yield *t_args
+      def thread_create(title)
         raise ArgumentError, "BUG: title must be a symbol" unless title.is_a? Symbol
         raise ArgumentError, "BUG: callback not specified" unless block_given?
         m = Mutex.new
         m.lock
-        thread = ::Thread.new(*args) do |*t_args|
+        thread = ::Thread.new do
           m.lock # run thread after that thread is successfully set into @_threads
           m.unlock
           thread_exit = false
           ::Thread.current[:_fluentd_plugin_helper_thread_title] = title
           ::Thread.current[:_fluentd_plugin_helper_thread_started] = true
           ::Thread.current[:_fluentd_plugin_helper_thread_running] = true
           begin
-            yield *t_args
+            yield
             thread_exit = true
           rescue => e
             log.warn "thread exited by unexpected error", plugin: self.class, title: title, error_class: e.class, error: e