Groups > comp.lang.java.programmer > #12607

Re: Strange Socket problem

From	Lew <noone@lewscanon.com>
Newsgroups	comp.lang.java.programmer
Subject	Re: Strange Socket problem
Date	2012-03-02 16:00 -0800
Organization	albasani.net
Message-ID	<jirmv1$1gj$1@news.albasani.net> (permalink)
References	<jiojsa$5ol$1@dont-email.me> <4f512b27$0$26687$65785112@news.neostrada.pl> <jirjpg$rkb$1@news.albasani.net> <jirlma$bfm$1@dont-email.me>

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Knute Johnson wrote:
> The volatiles exist because the methods that access them can be called from
> other threads. I could have synchronized the start() stop() methods but not
> easily the socket variable in the run() method. I thought it was cleaner to
> just use volatile.

I see a problem right there.

>     public void disconnect() {
>         if (isConnected())
>             if (socket != null)
>                 try {
>                     socket.close();
>                 } catch (IOException ioe) {
>                     ioe.printStackTrace();
>                 }
>     }

Since these are controlled by separate synchronization (different 'volatile' 
variables) there's a race condition trying to work with both at once.

Also, 'socket' can become 'null' between the check for not 'null' and the 
'close()' call.

You need to synchronize with 'synchronized' or other strong mechanism.

-- 
Lew
Honi soit qui mal y pense.
http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg

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Thread

Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-01 11:49 -0800
  Re: Strange Socket problem Steven Simpson <ss@domain.invalid> - 2012-03-01 20:59 +0000
    Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-01 13:30 -0800
      Re: Strange Socket problem Steven Simpson <ss@domain.invalid> - 2012-03-01 22:54 +0000
        Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-01 16:32 -0800
          Re: Strange Socket problem Steven Simpson <ss@domain.invalid> - 2012-03-03 09:08 +0000
            Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-03 17:48 -0800
  Re: Strange Socket problem markspace <-@.> - 2012-03-01 14:08 -0800
    Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-01 16:48 -0800
      Re: Strange Socket problem markspace <-@.> - 2012-03-02 08:33 -0800
        Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-02 15:29 -0800
          Re: Strange Socket problem markspace <-@.> - 2012-03-03 09:33 -0800
            Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-03 17:55 -0800
              Re: Strange Socket problem markspace <-@.> - 2012-03-03 20:06 -0800
                Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-03 21:02 -0800
                Re: Strange Socket problem "John B. Matthews" <nospam@nospam.invalid> - 2012-03-05 00:00 -0500
                Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-05 09:44 -0800
  Re: Strange Socket problem Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-01 22:15 +0000
    Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-01 16:43 -0800
      Re: Strange Socket problem Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-03 02:01 +0000
  Reiteration: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-01 16:51 -0800
    Re: Reiteration: Strange Socket problem Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-03 02:02 +0000
  Re: Strange Socket problem x <x@x.x> - 2012-03-02 21:18 +0100
    Re: Strange Socket problem Lew <noone@lewscanon.com> - 2012-03-02 15:06 -0800
      Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-02 15:38 -0800
        Re: Strange Socket problem Lew <noone@lewscanon.com> - 2012-03-02 16:00 -0800
          Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-02 17:18 -0800
            Re: Strange Socket problem Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-03 02:13 +0000
              Re: Strange Socket problem Steven Simpson <ss@domain.invalid> - 2012-03-03 08:41 +0000
                Re: Strange Socket problem Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-03 18:26 +0000
        Re: Strange Socket problem x <x@x.x> - 2012-03-03 11:32 +0100
          Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-03 17:59 -0800
          Re: Strange Socket problem Lew <noone@lewscanon.com> - 2012-03-03 23:21 -0800
      Re: Strange Socket problem x <x@x.x> - 2012-03-03 10:59 +0100
        Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-03 18:08 -0800
    Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-02 15:33 -0800
  Re: Strange Socket problem Paka Small <paka-en@tumia.org> - 2012-03-03 03:32 -0800
    Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-03 18:00 -0800
  Re: Strange Socket problem x <x@x.x> - 2012-03-03 12:45 +0100
    Re: Strange Socket problem Knute Johnson <nospam@knutejohnson.com> - 2012-03-03 18:02 -0800

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