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Date: Tue, 14 Nov 2017 17:55:46 +0100 (CET)
From: Julia Lawall <julia.lawall@lip6.fr>
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To: "Luis R. Rodriguez" <mcgrof@kernel.org>
cc: Masahiro Yamada <yamada.masahiro@socionext.com>, cocci@systeme.lip6.fr,
        Michal Marek <michal.lkml@markovi.net>,
        Nicolas Palix <nicolas.palix@imag.fr>, linux-kernel@vger.kernel.org,
        linux-kbuild@vger.kernel.org
Subject: Re: [Cocci] [PATCH v3] coccinelle: fix parallel build with
 CHECK=scripts/coccicheck
In-Reply-To: <20171114165221.GF729@wotan.suse.de>
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On Tue, 14 Nov 2017, Luis R. Rodriguez wrote:

> On Tue, Nov 14, 2017 at 06:04:49PM +0900, Masahiro Yamada wrote:
> > diff --git a/scripts/coccicheck b/scripts/coccicheck
> > index 040a8b1..7da82a1 100755
> > --- a/scripts/coccicheck
> > +++ b/scripts/coccicheck
> > @@ -70,6 +64,13 @@ if [ "$C" = "1" -o "$C" = "2" ]; then
> >      # Take only the last argument, which is the C file to test
> >      shift $(( $# - 1 ))
> >      OPTIONS="$COCCIINCLUDE $1"
> > +
> > +    # If -j option is given to Make, scripts/coccicheck runs in parallel.
> > +    # If coccinelle also runs in parallel, it fails because multiple processes
> > +    # try to get access to the same subdirectory that stores stdout/stderr.
> > +    # No need to parallelize coccinelle in this case - this mode takes only
> > +    # one file input.
> > +    NPROC=1
>
> Shouldn't this also warn to the user, and recommend to use a proper form to
> parallelize coccinelle? Otherwise a user might get the impression they are
> parallelizing coccinelle where they really did not.

Coccinelle sees a file at a time when using C=1 or C=2.  There is nothing
to parallelize at the Coccinelle level, if you want to use these options.

julia


>
>   Luis
>
> >  else
> >      ONLINE=0
> >      if [ "$KBUILD_EXTMOD" = "" ] ; then
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