waitpid_timeout_deadlock.rb

#!/usr/bin/env ruby

require 'timeout'

trap(:CHLD) { }

x = 0
while true
  puts "loop #{x += 1}"
  pid = Process.spawn('sleep 1')
  Timeout.timeout(30) do
    Process.waitpid(pid)
  end
end

waitpid_timeout_hang.rb

#!/usr/bin/env ruby

require 'timeout'

self_pipe = IO.pipe
signal_queue = []

def wake_up(self_pipe)
  self_pipe[1].write_nonblock('.', exception: false)
end

trap(:CHLD) { signal_queue << :CHLD; wake_up(self_pipe)  }

signal_processor = Thread.new do
  loop do
    self_pipe[0].read(1)
    signal_queue.pop
  end
end

x = 0
while true
  puts "loop #{x += 1}"
  pid = Process.spawn('sleep 1')
  Timeout.timeout(30) do
    Process.waitpid(pid)
  end
end