From: Alex Young <alex@...>
Date: 2011-02-10T20:59:27+09:00
Subject: What should TCPSocket#close do to a blocked #readline?

Take the following code:

  require 'socket'
  require 'thread'

  server = TCPServer.new("localhost", 0)
  serv_thread = Thread.new{ server.accept }
  sleep(0.1)
  sock = TCPSocket.new("localhost", server.addr[1])

  q = Queue.new
  client_thread = Thread.new{
    begin
      sock.readline
    rescue StandardError => e
      q.push(e)
    end
  }


  sleep(0.1) while client_thread.status == "run"
  sock.close
  # client_thread.wakeup rescue nil
  err = q.pop
  client_thread.join
  fail "Failure!" unless err.is_a?(IOError)
  puts "Success!"


So, we've got one thread blocked on a #readline, and another thread
closes the socket out from under it. On 1.8.7-p302, this completes
successfully. On 1.9.2-p136, it hangs at q.pop.

If I uncomment the client_thread.wakeup call, both complete (although
the rescue is necessary to prevent a ThreadError on 1.8.7).

Is this expected? Which is "correct"?

Thanks,
--
Alex

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