ActiveRecord::Base#silence / BufferedLogger Threadsafety Issues

ActiveRecord::Base#silence temporarily sets the logger to a higher level which is a no-go in a multithreaded environment. In case of config.threadsafe! (and true concurrency with JRuby) this more or less immediately leads to a quiet logger:

1. first thread sets level from e.g. 0 to 3
   
2. second thread comes along sees 3 as original log level
   
3. first thread finishes and sets the level to 0
   
4. second thread finished and sets level to 3

=> log level is screwed up.

IMO Temporary log level changes should generally be disabled when config.threadsafe!

Workaround: monkey-patch the method
module ActiveRecord
class Base

def self.silence
  yield
end

end end

Add then I think there is a system-level threadsafety issue, too: The level accessor methods of BufferedLogger are not protected from simultaneous changes.