The following demonstrates that Thread#wakeup can be used in a signal trap to wake up the thread that had control when the signal was raised. I have verified same behaviour in MRI (1.8.7, 1.9.3, 2.0.1, 2.1.1), JRuby (1.7.4, 1.9 mode), Rubinius (2.2.1), but testing signals is hard and I'm unsure how to verify this programatically.

gistfile1.txt

$ ruby ~/Desktop/sleepy.rb
signals registered.
^CCAUGHT INT!
4

sleepy.rb

# encoding: utf-8

module Sleepy
  def self.run(timeout)
    @sleepy = Thread.new do
      time = sleep(timeout)
      puts time.inspect
      time
    end

    %w(INT).each do |sig|
      trap(sig) do
        puts "CAUGHT #{sig}!"
        @sleepy.wakeup
      end
    end
    puts "signals registered."

    @sleepy.join
  end
end

Sleepy.run(20)