Remove defer support, required for large execution stacks on Ruby 1.9

lib/sidekiq/processor.rb

@@ -34,7 +34,6 @@ module Sidekiq
       msgstr = work.message
       queue = work.queue_name
 
-      do_defer do
       @boss.async.real_thread(proxy_id, Thread.current)
 
       ack = true
@@ -60,7 +59,6 @@ module Sidekiq
       ensure
         work.acknowledge if ack
       end
-      end
 
       @boss.async.processor_done(current_actor)
     end
@@ -71,22 +69,6 @@ module Sidekiq
 
     private
 
-    # We use Celluloid's defer to workaround tiny little
-    # Fiber stacks (4kb!) in MRI 1.9.
-    #
-    # For some reason, Celluloid's thread dispatch, TaskThread,
-    # is unstable under heavy concurrency but TaskFiber has proven
-    # itself stable.
-    NEED_DEFER = (RUBY_ENGINE == 'ruby' && RUBY_VERSION < '2.0.0')
-
-    def do_defer(&block)
-      if NEED_DEFER
-        defer(&block)
-      else
-        yield
-      end
-    end
-
     def identity
       @str ||= "#{hostname}:#{process_id}-#{Thread.current.object_id}:default"
     end