From: Alex Young <alex@...>
Date: 2011-02-11T01:10:48+09:00
Subject: Re: What should TCPSocket#close do to a blocked #readline?

Robert Klemme wrote in post #980828:
> On Thu, Feb 10, 2011 at 12:59 PM, Alex Young <alex@blackkettle.org>
> wrote:
>>
>> sleep(0.1) while client_thread.status == "run"
>> successfully. On 1.9.2-p136, it hangs at q.pop.
> I cannot confirm this:
>
> 15:40:10 Temp$ ruby19 -v
> ruby 1.9.2p136 (2010-12-25 revision 30365) [i386-cygwin]

$ ruby -v
ruby 1.9.2p136 (2010-12-25 revision 30365) [x86_64-linux]

is mine. Might it be an architecture issue? I don't have a 32bit machine
handy to compare.

> 15:40:50 Temp$ ruby19 s.rb
> #<IOError: closed stream>
> Success!
> 15:41:31 Temp$ cat s.rb
> 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
>      q.push "OK"
>    rescue StandardError => e
>      p 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!"
>
> 15:41:36 Temp$
>
>
>> 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"?
>
> Hm...  I would expect your 1.9.2 to also throw.

That's what I thought, but rubinius doesn't throw either, so I wasn't
sure.

>
> Btw, one thing is odd about your test case: you have two mechanisms to
> synchronize threads - you read from the queue and you join
> client_thread.

Yes, the #join was a bit of leftover that I forgot to trim.

> If you really only want to track status of the thread
> you could as well use Thread#value:
>
>  client_thread = Thread.new{
>    begin
>      sock.readline
>      nil
>    rescue StandardError => e
>      e
>    end
>  }
>
> err = client_thread.value
>

That's a bit neater, though. I like that.


Thanks,
--
Alex

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