Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
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
Message-ID:	<BAY19-F14865B312D569712E6C199B5450@phx.gbl>
X-Originating-Email:	[karlm30 AT hotmail DOT com]
X-Sender:	karlm30 AT hotmail DOT com
In-Reply-To:	<20050329084059.GH23860@cygbert.vinschen.de>
From:	"Karl M" <karlm30 AT hotmail DOT com>
To:	cygwin AT cygwin DOT com
Subject:	keychain locking problem (Was test -f occasionally fails on sym links)
Date:	Tue, 29 Mar 2005 06:47:37 -0800
Mime-Version:	1.0
X-OriginalArrivalTime:	29 Mar 2005 14:47:38.0176 (UTC) FILETIME=[406B7C00:01C5346E]
X-IsSubscribed:	yes

Hi All...

The reason I ask is that keychain uses

    if tl_error=`ln -s $$ "$lockf" 2>&1`; then

inside its takelock function as an atomic operation for creating a lock. It 
then uses

    if [ -f "$lockf" ]; then

to test for an old style lock file, and this sometimes fails (incorrectly 
succeeds) and generates an error message.

From what I can find, this is expected to be an atomic operation and one of 
the ways programs do file locking.

I ran into this when I did high load testing for the ssh-add hang problem.

In preparation for a keychain-service release, I provide an example, where I 
only run keychain on the first launched (login) shell (which also has the 
advantage of speeding things up substantially). To do this, I launch 
keychain as follows

    if (umask 0377; : > ~/.keychain/${HOSTNAME}-keys) 2>/dev/null; then
      keychain --quiet ~/.ssh/identity ~/.ssh/id_dsa ~/.ssh/id_rsa
    fi

and the lock file is cleaned up by the keychain-service. This does seem to 
be safe (only verified by load testing under Cygwin). I found this method in 
the UNIX CD Bookshelf.

So...my questions are

1) Is this a safe method?

2) Is there a better method for me to use in Cygwin?

3) Should this problem be fed to the upstream keychain maintainer?

Thanks,

...Karl

>From: Corinna Vinschen
>Subject: Re: test -f occasionally fails on sym links (keychain related)
>Date: Tue, 29 Mar 2005 10:40:59 +0200
>
>On Mar 25 09:37, Karl M wrote:
> > Sometimes doing a [ -f foo ]; will show a false true while the symlink 
>is
> > being created. You can see this by opening two bash shells and executing
>
>Creating symlinks is not an atomic process in Cygwin.  It requires
>several OS calls to create a symlink.
>
>
>Corinna



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

- Raw text -