From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <binutils-return-68940-listarch-binutils=sources.redhat.com@sourceware.org>
Received: (qmail 3646 invoked by alias); 2 Dec 2010 18:40:01 -0000
Received: (qmail 3574 invoked by uid 22791); 2 Dec 2010 18:40:00 -0000
X-SWARE-Spam-Status: No, hits=-2.2 required=5.0	tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW
X-Spam-Check-By: sourceware.org
Received: from mail-qy0-f169.google.com (HELO mail-qy0-f169.google.com) (209.85.216.169)    by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 02 Dec 2010 18:39:55 +0000
Received: by qyk7 with SMTP id 7so4125444qyk.0        for <binutils@sourceware.org>; Thu, 02 Dec 2010 10:39:53 -0800 (PST)
MIME-Version: 1.0
Received: by 10.229.222.13 with SMTP id ie13mr296814qcb.283.1291315193383; Thu, 02 Dec 2010 10:39:53 -0800 (PST)
Received: by 10.220.61.13 with HTTP; Thu, 2 Dec 2010 10:39:53 -0800 (PST)
In-Reply-To: <20101202183231.GD16143@gmx.de>
References: <20101202170032.GA19376@intel.com>	<20101202180829.GA16143@gmx.de>	<AANLkTikDiv+z6DtpZ8DT64gKDtcxsdycJVdNwbExCs7-@mail.gmail.com>	<20101202182050.GB16143@gmx.de>	<20101202182235.GC16143@gmx.de>	<20101202183231.GD16143@gmx.de>
Date: Thu, 02 Dec 2010 18:40:00 -0000
Message-ID: <AANLkTinwvK4yoDWUhGj3dFhemwsKHhoyhf47bb8=AA5s@mail.gmail.com>
Subject: Re: PATCH: PR binutils/12283: bfd/doc doesn't support parallel build
From: "H.J. Lu" <hjl.tools@gmail.com>
To: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>
Cc: binutils@sourceware.org
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
X-IsSubscribed: yes
Mailing-List: contact binutils-help@sourceware.org; run by ezmlm
Precedence: bulk
List-Id: <binutils.sourceware.org>
List-Subscribe: <mailto:binutils-subscribe@sourceware.org>
List-Archive: <http://sourceware.org/ml/binutils/>
List-Post: <mailto:binutils@sourceware.org>
List-Help: <mailto:binutils-help@sourceware.org>, <http://sourceware.org/ml/#faqs>
Sender: binutils-owner@sourceware.org
X-SW-Source: 2010-12/txt/msg00088.txt.bz2

On Thu, Dec 2, 2010 at 10:32 AM, Ralf Wildenhues <Ralf.Wildenhues@gmx.de> w=
rote:
> * Ralf Wildenhues wrote on Thu, Dec 02, 2010 at 07:22:35PM CET:
>> * Ralf Wildenhues wrote on Thu, Dec 02, 2010 at 07:20:50PM CET:
>> > * H.J. Lu wrote on Thu, Dec 02, 2010 at 07:16:07PM CET:
>> > > Failure is very random. There is a race condition. "make -j8" on a 1=
6core
>> > > machine can start making $(MKDOC) at the same time. How can move-if-=
change
>> > > be 100% atomic?
>> >
>> > Well, 'mv -f' within a mount point is atomic, that's how.
>>
>> Ahh, move-if-change is broken: it doesn't ignore mv -f failure when the
>> target is equal. =A0Let's fix move-if-change.
>
> Does this alternative (untested) patch fix the race?
>
> Thanks,
> Ralf
>
> ChangeLog:
> 2010-12-02 =A0Ralf Wildenhues =A0<Ralf.Wildenhues@gmx.de>
>
> =A0 =A0 =A0 =A0PR binutils/12283
> =A0 =A0 =A0 =A0* move-if-change: Ignore failure of 'mv -f' if the destina=
tion
> =A0 =A0 =A0 =A0is equal to the source afterwards.
>
> diff --git a/move-if-change b/move-if-change
> index ff74a55..1d2dd09 100755
> --- a/move-if-change
> +++ b/move-if-change
> @@ -4,6 +4,8 @@
>
> =A0usage=3D"$0: usage: $0 SOURCE DEST"
>
> +cmpprog=3D${CMPPROG-cmp}
> +
> =A0case $# in
> =A02) ;;
> =A0*) echo "$usage" >&2; exit 1;;
> @@ -18,5 +20,8 @@ done
> =A0if test -r "$2" && cmp -s "$1" "$2"; then
> =A0 rm -f "$1"
> =A0else
> - =A0mv -f "$1" "$2"
> + =A0if mv -f "$1" "$2"; then :; else
> + =A0 =A0# Ignore failure due to a concurrent move-if-change.
> + =A0 =A0$cmpprog "$1" "$2" >/dev/null 2>&1
> + =A0fi
> =A0fi
>

It is hard to test since it happens very much at random.


--=20
H.J.