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Re: PATCH: PR binutils/12283: bfd/doc doesn't support parallel build
* 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-if-change
> > > > be 100% atomic?
> > Ahh, move-if-change is broken: it doesn't ignore mv -f failure when the
> > target is equal. Let's fix move-if-change.
>
> Does this alternative (untested) patch fix the race?
Have you had a chance to try this out?
Thanks,
Ralf
> ChangeLog:
> 2010-12-02 Ralf Wildenhues <Ralf.Wildenhues@gmx.de>
>
> PR binutils/12283
> * move-if-change: Ignore failure of 'mv -f' if the destination
> 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 @@
>
> usage="$0: usage: $0 SOURCE DEST"
>
> +cmpprog=${CMPPROG-cmp}
> +
> case $# in
> 2) ;;
> *) echo "$usage" >&2; exit 1;;
> @@ -18,5 +20,8 @@ done
> if test -r "$2" && cmp -s "$1" "$2"; then
> rm -f "$1"
> else
> - mv -f "$1" "$2"
> + if mv -f "$1" "$2"; then :; else
> + # Ignore failure due to a concurrent move-if-change.
> + $cmpprog "$1" "$2" >/dev/null 2>&1
> + fi
> fi