X-Recipient:	archive-cygwin AT delorie DOT com
DomainKey-Signature:	a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:subject:message-id:reply-to
	:references:mime-version:content-type:in-reply-to; q=dns; s=
	default; b=WnU9J7Qef6AYlZIm73E0sfsmRrF9NTZhPeGOeKhEg0CT37ltnJwgV
	/9cvaLosG9gj8GCAFim9q2MtMUxrzPqlIE4wGBeEwEPYN+XzTxT3m2Hapgr4HKMu
	bjm0BsOvq8yqp6wgI7tkpvdmAZvExzs9nclKlFfm831L6u4HK1f29c=
DKIM-Signature:	v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:subject:message-id:reply-to
	:references:mime-version:content-type:in-reply-to; s=default;
	bh=u0QOPlWv5wXhM5ifFB6hL32wgIM=; b=w5iew8Rr1lkLZtbyIF5tUuj1rF06
	0KwyDpkBa2m1nmVE8VOzxQRlGbqlmOe1mx9WDwp2OsICKmnY14oFdH24lofm5eOy
	x5oJzkFRT5DIXGlDuOPOYygmJ/nF1rk36cSSy9ug9GhAAaWkk103KcgySlIbgV/V
	KtcuU5iOyPTh5M8=
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id:	<cygwin.cygwin.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
Authentication-Results:	sourceware.org; auth=none
X-Virus-Found:	No
X-Spam-SWARE-Status:	No, score=-96.5 required=5.0 tests=AWL,BAYES_00,GOOD_FROM_CORINNA_CYGWIN,KAM_LAZY_DOMAIN_SECURITY,RCVD_IN_PBL,RDNS_DYNAMIC autolearn=ham version=3.3.2 spammy=incurred, Kevin, occasionally, hangs
X-HELO:	calimero.vinschen.de
Date:	Tue, 24 May 2016 12:20:57 +0200
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: spinlock.h timeout causing *** fatal error - add_item abort
Message-ID:	<20160524102057.GB32753@calimero.vinschen.de>
Reply-To:	cygwin AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
References:	<D348D3EA.10AEB%knomura AT vmware DOT com>
MIME-Version:	1.0
In-Reply-To:	<D348D3EA.10AEB%knomura@vmware.com>
User-Agent:	Mutt/1.6.1 (2016-04-27)

--rS8CxjVDS/+yyDmU
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Apr 29 16:03, Kevin Nomura wrote:
> Hi,
>=20
> We occasionally see an api_fatal abort during process startup like:
>=20
> *** fatal error - add_item ("somepath", "/", ...) failed, errno 1
>=20
> This happens if mountinfo.init(false) in user_info::initialize is
> called twice.  The error occurs on a second call when trying to add
> the root mount point when it already exists.
>=20
> mountinfo.init is guarded by a "spinlock" object that should only
> allow one process to call it.  But the spinlock has a timeout.  After
> 15 seconds, it stops waiting and returns a value of 0.  The fatal
> error can occur if two processes are starting around the same time
> and the first process takes a long time in internal_getpwsid().  We've
> seen this happen in our environment due to LDAP queries taking a long
> time.  (Incidentally we are using msys, but code in spinlock.h and
> shared.cc looks the same in cygwin).
>=20
> To solve the aborts it is tempting to make a local fix to remove the
> spinlock timeout.  I assume there was a rationale for it, and would
> like to understand what tradeoff is incurred if we remove it.

Actually I can't tell you.  You might just want to try it and see if
it has some weird side-effect.  The problem this *probably* was
supposed to handle is that some process hangs in the initialization
indefinitely, thus blocking out other processes.  15 secs is just some
arbitrary big value.

The original reason to use a spinlock here wasbased on the idea that
reading fstabs and passwd/group files is quick, thus a spinlock is the
least intrusive locking mechanism.  This is obviously not true anymore,
now that fetching the user info may require network access.

I put an item on my TODO list to revisit this code and introduce
another, more reliable locking here.

For the time being you might want to try a spinlock with a longer
timeout (2 mins, perhaps)


Corinna

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

--rS8CxjVDS/+yyDmU
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2
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=ZO/p
-----END PGP SIGNATURE-----

--rS8CxjVDS/+yyDmU--

- Raw text -