X-Recipient:	archive-cygwin AT delorie DOT com
X-Spam-Check-By:	sourceware.org
Date:	Mon, 8 Mar 2010 14:56:57 -0500
From:	Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To:	"cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>,
	"Schmidt, Oliver" <oliv DOT schmidt AT sap DOT com>
Subject:	Re: Cygwin 1.7: Concurrency Issue with Shared State Initialization
Message-ID:	<20100308195656.GA17237@ednor.casa.cgf.cx>
Reply-To:	cygwin AT cygwin DOT com
Mail-Followup-To:	"cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>, "Schmidt, Oliver" <oliv DOT schmidt AT sap DOT com>
References:	<B10B50309DC54D45A855FD66F56015F71D07C78CAE AT DEWDFECCR03 DOT wdf DOT sap DOT corp>
MIME-Version:	1.0
In-Reply-To:	<B10B50309DC54D45A855FD66F56015F71D07C78CAE@DEWDFECCR03.wdf.sap.corp>
User-Agent:	Mutt/1.5.20 (2009-06-14)
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
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 Mon, Mar 08, 2010 at 06:35:02PM +0100, Schmidt, Oliver wrote:
>We call from a non-Cygwin shell a non-Cygwin gnumake.  The Makefile
>rules mostly call a non-Cygwin C compiler and linker.  However Makefile
>rules calling gawk, cat, cp, echo, mkdir, rm, sed, sh, ...  are calling
>Cygwin executables.
>
>If (and only if) we run gnumake in this scenario with the --jobs option
>to perform a parallel build then we experience sporadic failures of the
>Cygwin executables.  Fortunately these failures still happen now and
>then when running them with strace.  So it was quite easy to find out
>that the shared variable installation_root isn't correctly initialized
>when things go wrong.
>
>Checking out src/winsup/cygwin/shared.cc I stumbled over these lines
>
>    /* Initialize installation root dir. */
>     if (!installation_root[0])
>       init_installation_root ();

Yeah, that's one place that's missing synchronization.

I'll check in something tonight which attempts to solve this problem.
It's a somewhat tricky problem because adding a mutex here would slow
down every invocation of a cygwin program and we don't want to add to
the "Why is Cygwin so slow???" scenarios if we can help it.

cgf

--
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

- Raw text -