Date: Sat, 4 Sep 2010 11:26:26 +0200
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: 1.7.5: Occasional failure of CreatePipe or signal handing due to 	thread-unsafe code in cwdstuff::set
Message-ID: <20100904092626.GE16534@calimero.vinschen.de>
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On Sep  3 16:18, John Carey wrote:
> On Sep 03 12:37 Corinna Vinschen wrote:
> > On Sep  2 23:32, John Carey wrote:
> > > In Aug 17 10:15, Corinna Vinschen wrote:
> > > > I just released 1.7.6-1.
> > > ...
> > > > What changed since Cygwin 1.7.5:
> > > > ================================
> > > >
> > > > - Cygwin handles the current working directory entirely on its own.  The
> > > >   Win32 current working directory is set to an invalid path to be out of
> > > >   the way.  This affects calls to the Win32 file API (CreateFile, etc.).
> > > >   See http://cygwin.com/htdocs/cygwin-ug-net/using.html#pathnames-win32-api
> > >
> > > Thank you very much for the fix!
> > >
> > > I've been running tests against Cygwin 1.7.6, and then 1.7.7,
> > > and those sporadic, non-deterministic failures in CreatePipe
> > > did stop after the 1.7.6 upgrade, and are still gone in 1.7.7.
> > > I think it's been long enough to conclude that it is not just
> > > the non-determinism--it really is fixed, as expected.
> > >
> > > I understand that this issue opened a can of worms;
> > > thanks again for your efforts to overcome those difficulties.
> > 
> > I still don't like the final workaround, which is, to set the Win32 CWD
> > to the Cygwin CWD.  It would be nice if we could revert that change to
> > the pre-1.7.6 behaviour in a Vista-friendly way.  If you ever find out
> > how to make sure that the new handle in the PEB's user parameter block
> > is used even on Vista and later, pray tell me.
> 
> Thus far the only ideas I have come up with are somewhat
> shaky and go well beyond the documented Win32 API.
> (If only there was the equivalent of dup2(), but for Win32
> handles!!!)

ACK.

> Just how much undocumented behavior is
> tolerable, do you think?

Up to XP/2K3, we can simply set the handle in the user parameter block
and be done with it, just as in 1.7.5, but without the Vista workaround.

The problem only starts with Vista.  I have no objections to use
undocumented features, if they work.  If there's any way to replace the
cwd handle with our own *and* keep the Win32 API happy, I'll take it.


Corinna

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

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