demonstrating the behaviour of Mutex#sleep

gistfile1.rb

require 'thread'

mutex = Mutex.new

t1 = Thread.new do 
  mutex.synchronize do
    mutex.sleep
    # we've now been woken up, and we'll try and reacquire the mutex
    puts "woken up - mutex locked: #{mutex.locked?}"
  end
end

t2 = Thread.new do
  loop { break if t1.status == 'sleep' }
  # t1 is now sleeping on the mutex, so the mutex will be unlocked
  puts "t1 is sleeping - mutex locked: #{mutex.locked?}"
  # let's wake up t1
  t1.run
end

[t1, t2].map(&:join)