Re: [Xen-devel] [PATCH v2] stubdom: modify ioemu linkfarm only if necessary

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Dec 13, 2016 at 02:58:27PM +0100, Juergen Gross wrote:
> Several stubdom libraries are being rebuilt each time a top level make
> is called as they depend on stubdom/ioemu/linkfarm.stamp which is
> depending on tools/qemu-xen-traditional-dir. Unfortunately this
> directory is modified by each "make tools" call.
> 
> This can be avoided by writing stubdom/ioemu/linkfarm.stamp only if
> a source file beneath tools/qemu-xen-traditional-dir has been added
> or removed.
> 
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

though ...

> ---
> V2: maintain a list of the to be linked files in linkfarm.stamp and
>     rebuild this list at each make call for detecting any change
> 
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
>  stubdom/Makefile | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/stubdom/Makefile b/stubdom/Makefile
> index bc49cfe..38f1688 100644
> --- a/stubdom/Makefile
> +++ b/stubdom/Makefile
> @@ -298,9 +298,13 @@ ioemu/linkfarm.stamp: 
> $(XEN_ROOT)/tools/qemu-xen-traditional-dir
>       (cd $$src && find *     ! -type l  -type f  $(addprefix ! -name ,       
> \
>                       '*.[oda1]' 'config-*' config.mak qemu-dm qemu-img-xen   
> \
>                       '*.html' '*.pod'                                        
> \
> -                     )) |                                                    
> \
> -         while read f; do rm -f "$$f"; ln -s "$$src/$$f" "$$f"; done
> -     touch ioemu/linkfarm.stamp
> +                     )) >linkfarm.stamp.tmp;                         \
> +     cmp linkfarm.stamp.tmp linkfarm.stamp 2>/dev/null &&            \

I think we want 'cmp -s' here.

> +             rm linkfarm.stamp.tmp || {                              \
> +             mv linkfarm.stamp.tmp linkfarm.stamp;                   \
> +             cat linkfarm.stamp | while read f;                      \
> +                     do rm -f "$$f"; ln -s "$$src/$$f" "$$f"; done;  \
> +     }
>  else
>  export QEMU_ROOT
>  
> -- 
> 2.10.2
> 

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