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Date: Fri, 28 Apr 2006 12:42:15 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: rsync over ssh hang issue understood
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On Apr 28 06:25, Brett Serkez wrote:
> >This is really a tricky problem.  What I could do to circumvent this at
> >least for connections over ssh is to upload an OpenSSH test version
> >which uses socketpairs instead of pipes for the local connection to the
> >applications.  This avoids using pipes which are the culprit here,
> >apparently.    I would mark it as experimental version, but actually the
> >only difference would be that it would be a few per cent slower than the
> >version using pipes.  And that it probably doesn't hang.
> 
> It has been so long since I gave up on this that I forgot building my
> own version of rsync to do exactly this.
> 
> I've noticed multiple postings indicating issues with pipes.  Wouldn't
> it be better to track this down, it would likely fix multiple
> problems.

Sure, you're welcome to do this.  It's not exactly a problem to track it
down, it's to find a working solution which is the problem.  I wouldn't
offer the above temporary workaround if we had a solution.

The low-level problem is this: Cygwin's select(2) on the write end of
pipes always returns that the pipe is writable, since nobody has found a
test for the writablility of Windows pipes, which actually works correct.
For details see cygwin's source, file select.cc, function peek_pipe.

http://cygwin.com/acronyms/#PTC


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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