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Date: Sun, 19 Dec 2010 18:23:00 -0000
Message-ID: <AANLkTikAd7jWXN+2bi-OeR_-cQq7ivpSyVz+4165trVS@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
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On Sun, Dec 19, 2010 at 6:30 AM, Ralf Wildenhues <Ralf.Wildenhues@gmx.de> w=
rote:
> * Ralf Wildenhues wrote on Thu, Dec 02, 2010 at 07:32:31PM 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=
 16core
>> > > > machine can start making $(MKDOC) at the same time. How can move-i=
f-change
>> > > > be 100% atomic?
>
>> > 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?
>
> Have you had a chance to try this out?

It doesn't fail. But I couldn't reproduce the old problem anymore.


H.J.
> Thanks,
> Ralf
>
>> ChangeLog:
>> 2010-12-02 =A0Ralf Wildenhues =A0<Ralf.Wildenhues@gmx.de>
>>
>> =A0 =A0 =A0 PR binutils/12283
>> =A0 =A0 =A0 * move-if-change: Ignore failure of 'mv -f' if the destinati=
on
>> =A0 =A0 =A0 is 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 =A0rm -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
>



--=20
H.J.