X-Recipient: archive-cygwin AT delorie DOT com
X-SWARE-Spam-Status: No, hits=-1.2 required=5.0	tests=AWL,BAYES_00,T_RP_MATCHES_RCVD
X-Spam-Check-By: sourceware.org
Subject: Re: untarring symlinks with ../ fails randomly, silghtly OT
From: Wolf Geldmacher <wolf DOT geldmacher AT abacus DOT ch>
To: cygwin AT cygwin DOT com
In-Reply-To: <4E1301BC.3090809@cs.utoronto.ca>
References: <1309437783 DOT 2097 DOT 68 DOT camel AT geldmacher-pc>	 <20110630133703 DOT GE9552 AT calimero DOT vinschen DOT de> <4E0C90B2 DOT 2060409 AT cornell DOT edu>	 <1309447688 DOT 12904 DOT 21 DOT camel AT geldmacher-pc>	 <1309770955 DOT 22699 DOT 15 DOT camel AT geldmacher-pc>	 <20110704104656 DOT GA20822 AT calimero DOT vinschen DOT de>	 <20110705121059 DOT GI1457 AT calimero DOT vinschen DOT de>	 <4E1301BC DOT 3090809 AT cs DOT utoronto DOT ca>
Content-Type: text/plain; charset="UTF-8"
Date: Tue, 05 Jul 2011 19:01:41 +0200
Message-ID: <1309885301.331.1.camel@geldmacher-pc>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
X-IsSubscribed: yes
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
Precedence: bulk
List-Id: <cygwin.cygwin.com>
List-Unsubscribe: <mailto:cygwin-unsubscribe-archive-cygwin=delorie DOT com AT cygwin DOT com>
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sourceware.org/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com

On Tue, 2011-07-05 at 08:21 -0400, Ryan Johnson wrote:
> On 05/07/2011 8:10 AM, Corinna Vinschen wrote:
> > On Jul  4 12:46, Corinna Vinschen wrote:
> >> On Jul  4 11:15, Wolf Geldmacher wrote:
> >>> As an aside:
> >>> 	I also used to have some trouble with "rm -rf" of a directory
> >>> 	hierarchy failing more or less reproducibly (like: 80% of the
> >>> 	time) because files were presumably still "in use". Repeating
> >>> 	the command several times would succeed, though.
> >>>
> >>> 	Downgrading from cygwin1.dll/1.7.9.1 to cygwin1.dll/1.7.8.1
> >>> 	seems to have solved that issue as well - still have to see
> >>> 	the first "retry to delete".
> >>>
> >>> This may or may not be related to the original report, as it also reeks
> >>> of a race condition during file/directory operations.
> >> I can neither reproduce the tar problem, nor can I reprocude the rm
> >> problem.  I tried this under 2008R2 which is basically the same as your
> >> W7-64 bit.  I used local and remote drives to test the issue but to no
> >> avail.
> > Finally I managed to reproduce the problem and now I see what happens.
> >
> > Windows does not write back the file change timestamp unless the file
> > buffers are flushed.  This usually occurs at close time.  In contrast to
> > POSIX specifications the timestamps are *not* automatically updated when
> > a call to fetch file metadata is performed.
> >
> > Here's what tar does when creating the symlink:
> >
> >    1. create file with 000 permissions
> >    2. fstat
> >    3. close file
> >    [...]
> >    4. stat file
> >    5. if fstat.st_ctime != stat.st_ctime ==>  symlink placeholder has been
> >       overwritten.
> >
> > The problem is that the call to fstat on the opened handle gets some
> > value of the change time timestamp, but the subsequent close changes
> > the timestamp again.
> Wow. That must have been one hairy debug session... my hat goes off to you!
> 
> Ryan
Definitely agree! (Where's the "Like" button?)




--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple