From: Grigory Petrov <grigory.v.p@...>
Date: 2012-02-14T22:11:30+09:00
Subject: Why GIL is not released on ruby/dl external function call.

Hello.

if i run following test code:

require 'dl/import'
module User32
  extend DL::Importer
  dlload 'user32'
  extern 'int MessageBoxA(int, char*, char*, int)'
end
Thread.new { User32.MessageBoxA( 0, "Text", "Caption", 0 ) }
loop { sleep 1; puts( "loop running" ) }

I will see no "loop running" messages while message box is visible. So
i can suggest that Ruby is not releasing GIL while calling external
function via Ruby\dl. Why such weird architectural decision? This
prevents me from calling blocking functions in background thread :(.